TILBURG UNIVERSITY FACULTY OF CATHOLIC THEOLOGY

Persian Perspectives on Prima Philosophia

The influence of Avicenna’s interpretation of Aristotelian ontology on the De ente et essentia by

Saint Thomas Aquinas

Submitted in partial fulfillment of the

requirements for the MA/MPhil Theology and Religious Studies (research) and the ecclesiastical degree Sacrae Theologiae Baccalaureus (STB)

Supervisor by Prof. Dr. Rudi te Velde Alexis Szejnoga

2013

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Table of contents

Preface

4

Introduction

5

Chapter 1: The wider context of the De ente et essentia 9

Historical-philosophical context 9

Aristotelianism 10

Avicenna 11

Other sources: Liber de causis, Fons vitae and Averroës 12

The intent and scope of the De ente et essentia 15

Bibliographical information 16

The structure of the De ente et essentia 17

Reception of the treatise

19

Chapter 2: Avicennian influence on the De ente et essentia 21

Explicit references to Avicenna and his works 21

Implicit references to Avicennian thought 25

Avicennian influence on the De ente et essentia: De Raeymaeker 26

The development of the real distinction between essence and existence 29

Conclusion

32

Chapter 3: The content of the De ente et essentia 34

The different meanings of the words “esse” and “essentia” 34

How essentia is found in diverse things 35

How essentia is found in composed substances 35

How essentia is found in simple substances 36

The difference between God and the other simple substances 37

The real distinction between esse and essentia in substances other than God 38

The three ways in which essentia is found in substances 40

How essentia is found in accidents 41

How essences are signified by terms of first and second intention 42

A rejection of Platonism 44

Thomas Aquinas on universals 45

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Conclusion

46

Selected bibliography

54

Table 1: Explicit references to Avicenna in the De ente et essentia

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Table 2: Implicit references to Avicenna in the De ente et essentia

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Abstract 61

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Preface

Since this master thesis marks the completion of the first cycle in Catholic theology, I would

like to take this opportunity to express my sincere gratitude to a number of people who have

influenced my decision to study theology, and who have supported me along the way. My

interest in theology as an academic discipline started during my time at the Department of

International Affairs at PYU: many thanks to John Butt for introducing me to the joy of

theological debate, and to Martha Butt for being a paragon of Christian charity. Thanks to

Carool Kersten, for making erudition look cool, and for sparking an enduring interest in

Islamic philosophy in me; to Jeff Moynihan, for his extensive knowledge of statisticals.

Thanks to all my coworkers at the International Programs Office, in particular to Phi Noi and

Phi Daeng, and to all the international students that studied at PYU in the years in which I was

responsible for their well-being: you did a great job staying alive and out of prison, making

my job that much easier! But most importantly, thanks to Peggy Imai for believing in me and

my abilities, and for putting me to work in an environment where I would meet all these great

people. Without her positivity, her kindness, and her patient encouragement, none of this

would have come to pass.

I would not have survived five years abroad without the love and support of my adopted

family members: much love and thanks to James Kozak, Joe Taheri, Casey Gramaglia and

Dirk-Jan Arts for being like brothers to me. I sincerely cherish your friendship.

Thanks to my teachers at the Faculty of Catholic Theology, especially to Rudi te Velde for

supervising the writing of this thesis; to the members of the Thomas Institute for letting me

participate in their academic activities. Many thanks to my fellow students, both from

Catholic Theology and from the Honors Program, for their support and camaraderie.

Thanks to my family, first and foremost to my parents, for providing me with a place to work,

for oftentimes looking after my children while I worked on this thesis, and for their ongoing

support of my academic efforts; to my brother and sister, for everything. But most of all,

thanks to my wife Yui, my son Yarek and my daughter Helena, for their patience and support,

and for their love which at times was the only thing that kept me going.

I would like to dedicate this thesis to the loving memory of my late godfather, Alex Szejnoga,

who passed away during its composition, but who will never be forgotten.

“Nihil sine Deo”

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Introduction

The choice of a subject for this master thesis has been easy and straightforward. That it would

concern some aspect of the work of Saint Thomas Aquinas was clear from a very early stage:

my appreciation of his philosophical and theological thought predated my enrollment in the

research master program for Theology and Religious Studies, and was only strengthened by

my participation in the meetings of the Thomas Institute in Utrecht. That the subject of the

thesis would be related to metaphysics was also apparent from the start, as it is one of my

prime interests. The combination of these two factors offered a solution: the tractate De ente

et essentia. This succinct compilation of Aristotelian ontology, written by Thomas infra

magisterium, represents a first display of his firm grasp on metaphysics. In addition, it makes

for a good subject for a master thesis because plenty of literature concerning the tractate has

already been published: apart from his encyclopedic summary of theological insights, the

Summa Theologiae, no other literary work of Thomas Aquinas has been commented upon as

frequently as the De ente et essentia.

However, a simple summary of the contents of the De ente et essentia would not suffice for a

master thesis. I needed specific perspectives and questions to engage the text with. The first

question presented itself effortlessly: what was the historical-philosophical context in which

the De ente et essentia was written? It did not originate in an intellectual vacuum; a plethora

of individual philosophers and schools of thought influenced the young Dominican and

helped shape his view on classical Greek metaphysics. In the early thirteenth century, the

philosophical landscape was primarily dominated by the interaction between Christian and

Arabic culture. Less characterized by conflict than the clash of Christians and Muslims on the

borders of the Eastern Roman Empire, the mingling of cultures on the Iberian Peninsula

generated an exchange on philosophical, theological, and literary levels. The Latin West was

reintroduced to literary works of the ancient Greeks formerly deemed lost, through

translations of Arabic commentaries by multilingual inhabitants of al-’Andalus.

Among these newly recovered works were commentaries on the Metaphysics of Aristotle by

Ibn Sīnā, who would become known in the West by his Latinized name, Avicenna. Upon a

first reading of the De ente et essentia, it immediately became apparent that Thomas refers to

Avicenna quite a lot. Therefore, it appeared to me that Avicenna’s interpretation of

Aristotelian metaphysics posed a major influence upon Thomas. Commentators on the

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metaphysical though of Saint Thomas have come to a similar conclusion regarding the De

ente et essentia, although their reasoning is not always explicitly stated. James Weisheipl, a

Dominican scholar who authored an extensive biography of Thomas Aquinas, says of the De

ente et essentia: “This work is highly original, even though it is heavily indebted to

Avicenna’s Metaphysics”.1 Armand Maurer comments in the introduction to his English

translation of the De ente et essentia that it has an affinity with Thomas’s commentary on the

Four Books of Sentences by Peter Lombard, “both in their metaphysical notions and their

dependence on Avicenna”.2 Anthony Kenny states of the De ente et essentia: “The treatise is

heavily influenced by the eleventh-century Arabic philosopher Ibn Sina or Avicenna, whose

Metaphysics is referred to in the very first lines of Aquinas’ prologue”.3

All three authors

cited above not only mention Avicenna as an influence on the metaphysical thought of

Thomas, but they also do so in an exclusive manner (besides Avicenna no other influence is

mentioned) and in terms which denote more than a casual or minor influence (“heavily

indebted”, “dependent” and “heavily influenced”). This pointed me to a second specific

question to engage the text with: how exactly does the influence of Avicennian thought upon

Thomas become apparent within De ente et essentia?

Thus, my examination of the text of the De ente et essentia will be guided by questions

regarding the historical-philosophical context of the tractate, and concerning visible signs of

Avicennian influence within the text. This will be done in three consecutive steps. The first

chapter will present the historical and philosophical context of the De ente et essentia, its

bibliographical minutiae, and a diachronic summary of its reception among theologians and

philosophers alike. The second chapter will focus on the influence of Avicenna, and his

reading of Aristotle’s Metaphysics, on the De ente et essentia. This influence will be

examined by looking at explicit and implicit references to Avicennian thought made by

Thomas in the text of the opusculum, and by briefly reviewing a comparative study of the

ontologies of Thomas and Avicenna prepared by De Raeymaeker. The metaphysical content

of the De ente et essentia will be briefly summarized in the third chapter, with special

attention for traces of the philosophical thought of Avicenna. Because this influence only

becomes apparent within the content of the treatise, there exists some overlap between the

second and third chapters, for example when discussing the real distinction between essence

1 JAMES WEISHEIPL, Friar Thomas d’Aquino: His Life, Thought and Works, Garden City 1974, 79. 2 THOMAS AQUINAS, ARMAND MAURER, On Being and Essence, Torento 1968, 9. 3 ANTHONY KENNY, Aquinas on Being, New York 2002, 1.

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and existence in created beings. The conclusion will then summarize the main points of each

of the preceding chapters and present some corollary findings.

A few further remarks seem in order. First, I would like to comment on the relevance of this

master thesis. In all honesty, I find the modern emphasis on relevance somewhat

objectionable: a genuine intellectual interest does not need an excuse. However, within the

modern world of academics, in which only a limited number of research projects can be

funded, social relevance has become a deciding factor. I experienced it as quite difficult to

formulate the relevance of this thesis beyond the simple satiation of my personal desire to

know the answers to the questions with which I had decided to engage the text. However, in

the later stages of the preparation of this thesis, some social relevance started to dawn on me,

and it lay in the context of the De ente et essentia, rather than in its content. If we look at the

attitude of Thomas, we see that he is apparently open to a wide range of interpretations of

Aristotelian metaphysics, regardless of the religious affiliation of its authors. His

understanding of Christian theology is based upon a metaphysics which incorporates the

thought of Greek polytheists, Jews and Muslims just as easily as their Christian counterparts.

In addition, the intermingling of cultures seems to boost the intellectual progress of the

thirteenth century, and the availability of resources in different languages seems to be a

driving force behind this progress. The social relevance that I see is that an examination of the

influence of various Arabic philosophers and theologians upon the work of Thomas Aquinas

might serve as a possible and careful critique on the popular notion that Europe is culturally

based on Jewish-Christian roots, especially if this notion is used to defend positions

advocating a closure of Europe toward other cultures. Saint Thomas Aquinas, whose

teachings are considered to be the apex of Christian theology, did not achieve intellectual

greatness by closing his mind to other cultures, or by limiting his sources on the grounds of

the religious affiliation of their authors. This is the relevance of Thomas’s work that goes

beyond the intellectual interests of systematic theologians and philosophers alike.

A final opening remark concerns matters of methodology. All citations of the Latin text of the

De ente et essentia are taken from the Editio Leonina, with reference to the chapter (or “P” for

proöemium or introduction) and line number(s).4

4 Sancti Thomae de Aquino Opera omnia, Tomus XLIII, Roma 1976.

Citations from the English text are taken

from Bobik’s Aquinas on Being and Essence: A Translation and Interpretation, with

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reference to the page number.5 Reference to the titles of philosophical works is in the original

language, with a translation in English within parentheses upon its first occurrence in the text.

Whenever an original text was not written in Latin, the Latin title is used whenever Thomas

refers to a Latin translation. Thus Avicenna’s Ilāhiyyāt (Metaphysics) refers to the Arabic

original, while Avicenna’s Metaphysica (Metaphysics) refers to the Latin translation of the

text. In those cases where Latin titles might be referring to different texts (for example, the

Sufficientia or the Metaphysica), the context should clarify which version is meant. I have

used the American-English way of spelling throughout this thesis, and followed The Chicago

Manual of Style for stylistic purposes.6

5 JOSPEPH BOBIK, Aquinas on Being and Essence: A Translation and Interpretation, Notre Dame 1965.

The critical apparatus and style of the bibliography

conform to the style taught at the Faculty of Catholic Theology.

6 The Chicago Manual of Style, Chicago/London 2010.

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Chapter 1: The wider context of the De ente et essentia

In this chapter, we will take a look at the context in which the De ente et essentia was written.

The first part will focus on historical-philosophical aspects, treating topics like the renewed

interest in Aristotelian philosophy, the attention being paid to translations of Arabian works

on theology and philosophy, notably of Avicenna and Averroës, and to two philosophical

treatises, the Fons vitae and the Liber de causis, which were at the time wrongly attributed to

Aristotle and an unknown Christian theologian. In addition, we will look at some

bibliographical details of the De ente et essentia: an approximation of the period in which it

was written, the rationale behind its structure, a summary of its intent and scope, and its

reception among medieval and modern philosophers.

Historical-philosophical context

In order to shed light on the historical-philosophical context of the De ente et essentia, it is

first necessary to determine precisely when this opusculum was written. Bartholomew of

Lucca (c. 1236 - c. 1327), disciple and confessor to Thomas Aquinas, mentioned the

manuscript in his list of works by his fellow Dominican as Tractatus de ente et essentia quem

scripsit ad fraters et socios nondum existens magister (Treatise on Being and Essence, which

he wrote for his Brothers and Colleagues, while not yet a Master). Thomas’s graduation at the

theological faculty of the University of Paris has been reliably determined to have taken place

in March 1256, and the De ente et essentia can therefore safely be assumed to have been

written before then. It is generally agreed upon that he wrote the treatise while lecturing on

the Libri quattuor sententiarum (Four Books of Sentences) of Peter Lombard (c. 1096 – 1164)

at the University of Paris. This means that the De ente et essentia was probably written after

his departure from Cologne, where he had been studying under Albert the Great (1193/1206 -

1280), in 1252. This limits the possible composition of the treatise within a four-year window.

Four more works survive from this period: the oration that Thomas held at the beginning of

his stint as baccalaureus sententiarius, his oration to commemorate his acceptance of the task

of a magister in sacra pagina, his commentary on the Libri quattuor sententiarum by Peter

Lombard (Scriptum super libros sententiarum), and the De principiis naturae (On the

Principles of Nature). As both orations have been composed at the limits of our possible

timeframe, the only question that remains is the order in which the other three works were

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written. Because Thomas probably wrote the Scriptum super libros sententiarum based on his

notes for classes, he must have worked on this work continuously while teaching in Paris.

Regarding the other two works, it is generally assumed that De principiis naturae was

composed before the De ente et essentia. However, for the purpose of this thesis, the date of

composition will be considered to be no earlier than Thomas’s arrival in Paris in 1252, and no

later than his graduation as magister in sacra pagina in 1256, without further delineation.

This means that for the construction of a summary of possible influences on Thomas’s

metaphysical thought, no events postdating 1252 will be considered.

Aristotelianism

In the broadest sense, Aristotelianism denotes the entire field of philosophy that is primarily

inspired by the thought of the Greek philosopher Aristotle (384-322 BCE). In a way, he

himself can be thought of as the founder of the tradition that bears his name, seeing as how he

started the Lyceum in Athens, a school that educated students in his peripatetic tradition.

Later philosophical movements became interested in his thought, causing renewed interest in

his teachings. The first resurgence of Aristotelian philosophy in the Common Era happened

with the advent of Neo-Platonism in the third century, starting with the philosophy of Plotinus

(204-270). Having become interested in the works of Plato (428-348 BCE), this school of

thought extended its view to include the writings of his student Aristotle, commentating and

expanding on them.

Starting in the ninth century, Islamic philosophers and theologians began translating and

commenting upon Aristotle’s work. Al-Kindī (801-873, also known by his Latin moniker

Alkindus), an Arabic polymath who has become known among Muslims as “the father of

Islamic philosophy”, wrote a commentary on Aristotelian logic. In the tenth century, al-Fārābī

(872-950, known in the West as Alpharabius) commented on Aristotle’s treatise on logic, the

Organon. At the turn of the millennium, the Persian physician Ibn Sīnā (980-1037, called

Avicenna in Latin) became interested in Aristotle’s Metaphysics, and wrote a commentary on

it. His influence on the metaphysics of Thomas Aquinas will be treated in detail below. The

Persian theologian al-Ghazālī (1058-1111, also called Algazel in Latin) wrote extensively on

Aristotle’s logic and metaphysics. Ibn Rushd (1126-1198, known as Averroës) was one of the

last of the Islamic philosophers to comment on the works of Aristotle, but he was also one of

the most prolific writers on Aristotelian topics. Because of his extensive writing on Aristotle,

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and because of the fact that he lived in al-‘Andalus rather than beyond the border of the

Eastern Roman Empire, he became one of the most influential philosophers in the Latin West,

after the translation of his work by Michael Scot (1175-1232) in the twelfth century.

That this new appreciation of Aristotelian thought was not always approved of by church

authorities became perfectly clear in 1210, when the provincial synod of Sens prohibited the

reading of Aristotle’s works on natural philosophy in the city of Paris, under threat of

excommunication. This prohibition also applied to commentaries on Aristotelian literary

works. However, the synod’s ruling was apparently limited to students of the faculty of arts at

the University of Paris, and theology students were still free to read Aristotle whenever they

wanted. This explains why Thomas had no qualms about writing, and making available, his

De ente et essentia.

Avicenna

The final influence on Thomas Aquinas to be individually treated here, and the one of which

the influence will be traced throughout the De ente et essentia, is that of Avicenna. This

Persian polymath, who had the reputation of being somewhat of a genius (he claimed to have

known the Qur’ān by heart at age seven), wrote extensively on such diverse subjects as

medicine, geology, metaphysics and psychology. In addition to this, Avicenna also wrote

multiple volumes of poetry, as well as composing parts of his scientific works in verse. He

was also a devout Muslim, and part of his intellectual calling was to synthesize kalām, or

Islamic theology, with the philosophical schools of Plato and Aristotle.

Avicenna was in fact so successful in reconciling Islamic theology with Greek philosophical

thought, that he became the main proponent of Islamic philosophy in the twelfth century.

However, in Europe his teachings would not be accepted as easily. His writings were met with

heated discussions, for example about the real distinction between being and essence and the

creation of the world through necessary emanation, which lead to a proscription of his work in

the city of Paris in 1210 (sharing the fate of Aristotle’s intellectual heritage). By the time that

Thomas Aquinas arrived in Paris in 1252, this prohibition must have been lifted or otherwise

weakened, as Maurer notes that Avicenna was “in vogue” while Thomas taught in Paris.1

1 THOMAS AQUINAS, ARMAND MAURER, On Being and Essence, Toronto 1968, 8-9.

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The thought of the real distinction between existence and essence, or between esse and

essentia to use Latin nomenclature, was arguably first formulated by Avicenna. It means that

on an ontological level, there is a difference between what an object is (its essentia or

essence), and that an object is (its esse or existence). Admittedly, the distinction itself was

already formulated by Aristotle in his Analytica posteria and his Metaphysics. However, it is

argued that Avicenna is the first to uphold the distinction on a metaphysical level, whereas

Aristotle limited it to an analytical level. The real distinction between being and essence will

be one of the specific points that will be traced in the De esse et essentia. Its formulation by

Avicenna and the context in which it arose will be treated in chapter 2 of this thesis.

The literary output of Avicenna was enormous. Most famous among his many works is the

Kitāb ash-Shifā’ (Book of Healing), an encyclopedia of philosophical thought. It was entitled

“Book of Healing” because through the wisdom that it held, it “healed” the reader of his

ignorance, which according to Avicenna should be regarded as a sickness of the mind. Parts

of this encyclopedia would be translated into Latin, and as such they were known to Thomas.

That part of the Kitāb ash-Shifā’ which had theological and metaphysical subjects as its topics

(Ilāhiyyāt), was translated into Latin as the Metaphysica. This was a new treatise on the

subject, not a commentary on the work of the same name by Aristotle. Likewise, the part

which treated on physics was translated into Latin and was known by the name of Sufficientia,

which is also the Latin title for the entire Kitāb ash-Shifā’. That part of the encyclopedia

dedicated to psychology (al-Nafs’) was translated as De anima. Finally, al-Mantiq, the part

that expounded Avicenna’s thought on logic, was known in Latin as the Logica. Although

only the Metaphysica and the De anima are explicitly referred to by Thomas, we can trace the

influence from all these four parts of the Kitāb ash-Shifā’ in the De ente et essentia.

Other sources: Liber the causis, Fons vitae and Averroës

A specific work of philosophy that deserves mention here is the Liber de causis (Book of

Causes), which in 1252 was still attributed to Aristotle. It treats the problematic relationship

between the One and the Many, or how multiplicity can originate from unity. To bridge the

apparent chasm between simplicity and diversity, the author posits the Spirit, which is both

singular and a principle of diversity, and which includes in itself the multiplicity of Forms.

Through the mediation of the Spirit, the One brings about the existence of the Soul, which in

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the Neo-Platonic tradition must be understood as the Soul of the World. It should be clear that

this mediated creation of the Soul posed a problem for Islamic and Christian philosophers, as

it touched upon certain tenets of Gnostic heresies.

Although unknown to Thomas Aquinas when he wrote the De ente et essentia, he later

discovered that the Liber de causis had in fact not been written by Aristotle, as its contents

were largely copied from the Stoicheiosis theologikè (Elements of Theology, better known by

its Latin title Elementatio theologica) by Proclus (412-485). Thomas made this discovery after

having received a translation of the works of Proclus from his friend and fellow Dominican

William of Moerbeke (1215-1286), and reported on his findings in the proöemium of his

Super librum de causis expositio (Commentary on the Book of Causes).2

Although the author

of the Liber de causis has still not been identified with certainty, it is believed that he was a

Muslim philosopher or theologian, who set forth to synthesize the Neo-Platonic doctrine of

emanation with the Islamic theology of creation. As such, the work is a combination of

thoughts from both Proclus and Plotinus (204-270).

Another proponent of Neo-Platonism that has exerted a major influence on the De ente et

essentia, was the Hebrew philosopher Solomon Ibn Gabirol (1021-1058) from al-’Andalus,

who became known in the Latin West as Avicebron. Although an accomplished poet, he will

primarily be remembered as one of the first philosophers to introduce Neo-Platonism to

Western Europe. A collection of five tractates on matter and form, known by its Latin title as

De materia et forma, or alternatively as Fons vitae (this is the name that Thomas refers to),

was translated from Arabic into Latin in 1150. It should be noted that Thomas Aquinas, and

his scholastic intellectual heirs, were of the opinion that the author of the Fons vitae was a

Christian philosopher. It was only in 1846, when Solomon Munk discovered a Hebrew

translation of the Arabic original of the Fons vitae, that it was concluded that Avicebron was

in fact none other than Solomon Ibn Gabirol.

The five tractates of the Fons vitae presented several aspects of the doctrine of matter and

form. Among these were the relationship between matter and form in physical substances, the

existence of substantiae simplices which form an intermediary level between the prima 2 THOMAS AQUINAS, VINCENT GUAGLIARDO O.P., CHARLES HESS O.P., RICHARD TAYLOR (TRANSLATORS), Commentary on the Book of Causes, Washington D.C. 1996, 4. For the Latin text: SANCTI THOMAE DE AQUINO, H.D. SAFFREY O.P. (EDT), Super librum De Causis expositio, Freiburg/Leuven 1954, or Sancti Thomae de Aquino Opera omnia, Tomus XLIX, Roma (in preparation).

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essentia (God) and physical creation, and the thought that all created substances are composed

of matter and form, even spiritual substances (a point of contention with Thomas). Moreover,

Avicebron posits that all matter is one, although it becomes less spiritual as it is farther

removed from the prima essentia. As Avicebron tried to strictly separate his philosophical

thoughts from his religious beliefs, it can be contested whether the Fons vitae presents an

attempt to reconcile Neo-Platonic philosophy with Jewish theology.

Among the commentaries upon the works of Aristotle, none were as valued by Thomas

Aquinas as those of Averroës, to which he routinely refers as “the Commentator”, rather than

by his given name. It is through the translation of his commentaries into Latin, in the twelfth

century, that the Latin West was reintroduced to the philosophy of Aristotle. Averroës wrote

commentaries on all the works of Aristotle with the sole exception of the Politics, which was

unavailable to him. Averroës attempted to reconcile Aristotelian philosophy with Islamic

theology and wrote against the resurgence of Neo-Platonism, for instance in the philosophical

works of Avicenna. His system of thought is referred to as Averroism.

The term Averroism has also been applied to the reception of his philosophy by such

Christian theologians as Siger of Brabant and Boetius of Dacia, who both went on to teach at

the university of Paris.3

However considering their ages, their thoughts on Averroës could not

have influenced Thomas Aquinas while writing the De ente et essentia. It is more likely that

Mosheh ben Maimon (1135-1204), a Jewish philosopher who was also known by his Latin

moniker Maimonides, introduced Thomas to Averroism. His writings proposed a synthesis of

Aristotelian philosophy and biblical theology which alarmed church authorities to the extent

that they confiscated rabbinic texts in Spain and the South of France.

The philosophy of Averroës included various standpoints that could be deemed problematic to

Christian theologians and to church authorities. For one, Averroës taught that the truth was

accessible by use of the intellect, and not just through faith. Another tenet of his school of

thought which went against Christian (and Islamic) theology was the belief that the world was

eternal, thus making impossible the creation of the world ex nihilo. Averroës also proposed

that there existed but a single intellect, which all humans share. This particular view was 3 The date of birth and precise date of death is not known for both these men. We know of Siger of Brabant that he was born between 1235 and 1240, and that he died between 1280 and 1284. Even less is known of Boetius of Dacia. His date of birth constitutes a completely unknown factor, while the date of his death is thought to be around 1284.

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attacked by Thomas in his De unitate intellectus contra Averroistas (On the unity of intellect

against the Averroists). Although Averroës exerted great influence upon the thought of

Thomas Aquinas, it must be noted that their relation was characterized by disagreement: most

of the time Thomas develops his own standpoint as a refutation of Averroës.

To summarize the historical-philosophical influences working on Thomas Aquinas while he

was writing the De ente et essentia, it can be stated that there existed two opposed movements.

First of all there was a renaissance of Greek philosophy as a result of recent translations into

Latin of the works of Aristotle and Neo-Platonists, which had been commented upon by

Islamic philosophers and theologians. The Muslim commentators had tried to reconcile, in

varying degrees of success, Aristotelian and Neo-Platonic thought with Islamic theology,

which made it all the more attractive to Christian thinkers. Added to these sources were the

occasional thoughts of Jewish philosophers living in al-’Andalus. The main aim of Muslim

intellectuals had been a synthesis of philosophy and theology.

On the other hand, a backlash occurred when church authorities learned of the new influence

of pagan philosophers at the universities of Europe. This resulted in prohibitions and

confiscations of philosophical treatises, under threat of excommunication. Thus resurgence

was met with repression. The intellectual climate was one of new challenges and possibilities,

while at the same time heated discussions flared between the proponents of opposing

viewpoints. It was in this era of renewed interest in Greek philosophy that Thomas Aquinas

wrote his De ente et essentia.

The intent and scope of De ente et essentia

Three different possibilities are documented as to why Thomas Aquinas composed the De

ente et essentia. The first possibility can be gleaned from the dedication “ad fratres et socios”,

added to the title given to the opusculum by Bartholomew of Lucca. This could refer to

Thomas’s fellow monks at Saint James, the Dominican study house where Thomas stayed

during his time as a baccalaureus sententiarius at the University of Paris. It is quite

conceivable that some of his associates at the house asked him to explain the basic notions of

Aristotelian ontology to them. A second possibility is that Thomas was asked by his teachers

at the theological faculty to write the treatise as a proof of his grasp of the metaphysics of

Aristotle, thus indicating that he was in fact ready to assume the tasks of a magister in sacra

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pagina. Yet another possibility would be that Thomas was asked to write the opusculum by

his Dominican superiors, to estimate Thomas’s position in the various discussions that raged

over Aristotelian topics. This is a feasible possibility because Thomas already had quite a

name as being well versed in Aristotelian philosophy. Moreover, he was new to the Parisian

scene, having just arrived from Cologne, where he had studied under the wing of Albert the

Great, who was known to be greatly influenced by Avicenna’s epistemology. However, in my

opinion, the first possibility is still the most plausible, considering the multitude of titles and

subtitles of known manuscripts of the De ente et essentia, in which the treatise is dedicated to

his fellow Dominicans at Saint James. In addition, there is no written evidence to support the

claim that either the Parisian teachers or Thomas’s superiors within the order doubted the

integrity and ability of the young Dominican.

Whatever the exact reason was for Thomas to write the De ente et essentia, its intent seems

perfectly clear: to summarize and comment upon certain elements of Aristotelian ontology, as

set forth in his Metaphysics. It is therefore a purely philosophical treatise, somewhat of an

anomaly within the mostly theological corpus Thomisticum. Specifically, the De ente et

essentia seeks to carefully explain exactly what is meant by the two terms mentioned in its

title: being (ens) and essence (essentia). However, the emphasis lies heavily on essence,

which Thomas also calls natura (nature) and quiditas (quiddity or “whatness”). As stated in

the prologue of the De ente et essentia, Thomas is not merely interested in explaining the

exact meaning of being and essence; he also wants to expound on the (three) ways in which

they can be found in substances, and on their relationship to the logical concepts of genus,

species and differentia.

Bibliographical information

The De ente et essentia is available to us through no less than 189 complete manuscripts, a

number only exceeded by Thomas’s Summa Theologiae. These manuscripts have been given

different titles by those who wished to catalogue the works of Saint Thomas. Bartholomew of

Lucca first recorded the opusculum as De quiditate et esse, and on a later occasion as

Tractatus de ente et essentia quem scripsit ad fraters et socios nondum existens magister. In

1319, when Bartholomew of Capua prepared a catalogue of the works of Thomas as one of

the necessary steps toward canonization, the treatise was called De ente et essentia. The

opusculum was recorded as Tractatus de quiditate entium seu De esse et essentia ad fraters et

17

socios by Dominican inquisitor Bernard Gui, Saint Antoninus of Florence and Ludwig von

Vallodolid.

Starting in the early fourteenth century, the treatise was also included under different titles in

the catalogues of several libraries. In France, the work was called De entium quiditate

(Avignon), Incipit tractatus de ente et essentia compositus a fratre Thoma de Aquino

(Bordeaux) or Tractatus de essentia (Paris). In a catalogue from Corpus Christi College in

Oxford, England, the opusculum was listed as tractatus fratris Thome de ente. The

identification of Thomas Aquinas as “brother” rather than “saint” points at an appellation

before 1323.

Martin Grabmann notes that the De ente et essentia of Saint Thomas is not the only treatise

bearing that name, although he persists that Thomas was the first to write a tractate on being

and essence, setting an example for later opuscula on this specific topic and thus acting as the

progenitor of this specific literary genre. He lists Giles of Rome, Bernard of Trilia, Hervaeus

Natalis and Theodoric of Freiberg as other authors who wrote on the topic, and whose work

has become known as De ente et essentia or similar titles.4

The structure of the De ente et essentia

The structure of the De ente et essentia is quite evident as Thomas remarks on the reasons

behind his organization of the text. Already in the proöemium of the treatise, Thomas presents

the threefold “agenda” of the De ente et essentia: “we must point out what is signified by the

words “being” and “essence,” and how they are found in diverse things, and how they are

related to the logical intentions, genus, species and difference”. 5

4 MARTIN GRABMANN, ‘Die Schrift “De Ente et Essentia” und die Seinsmetaphysik des heiligen Thomas von Aquin.’, in: MARTIN GRABMANN, Mittelalterliches Geistesleben, München 1926.

These three prime tasks

which Thomas sets himself constitute the key structuring elements of the De ente et essentia.

However, these three tasks are then further differentiated by another maxim: “we ought to

acquire knowledge of what is simple from what is composed, and come to what is prior from

what is posterior, so that, beginning with what is easier, we may progress more suitably in

5 “dicendum est quid nomine essentie et entis significetur, et quomodo in diversis inveniatur, et quomodo se habeat ad intentions logicas, genus, speciem et differentiam “. Leon. 43.P:7-10.

18

learning”.6

Because of this principle Thomas resolves to treat the word “being” before the

word “essence”, because being is prior to essence, at least with regard to intellectual

understanding.

With regard to the second task, the exposition of how being and essence are found in diverse

things, the idea of starting with what is composed or posterior is also used to apply further

differentiation. Thomas remarks how “being” can be used in two different ways: on the one

hand with regard to the things which can be determined into the ten genera of Aristotle

(substances and accidents), on the other hand “being” can be used to signify the truth of

(affirmative) propositions. Included in the use of the word “being” in this second sense are

negations and privations, which will not be treated in the De ente et essentia because they lack

essences. The things that are signified by the word “being” used in the first sense can be

subdivided in two different ways: first we differentiate between things which fall into

Aristotle’s first category and are called “substances” on account of their independent being,

and things which fall into the remaining nine categories and are called “accidents” on account

of their dependence on substances. Thomas will treat substances first because they may be

considered without any thought being given to accidents, but accidents can only be considered

in connection to substances. Secondly, we can further subdivide the substances into composed

or corporeal substances, of which we have sensory experience, and simple or incorporeal

substances of which we have no sensory experience (angels, for example). Here the maxim

applies that the composed should be considered before the simple and Thomas thus treats the

composed or corporeal substances first. It should be noted that the differentiation of the

second and third tasks stems from the execution of the first task, namely the examination of

the meaning of the word “being”.

Having taken all the above into consideration, the structure of the De ente et essentia becomes

clear: after the opening words of the proöemium, Thomas will deal with the first task of

examining the meaning of the words “being” and “essence”. Next, he takes a look at the

composition of existence and essence in corporeal substances. He then goes on to discuss the

relationship between essences and the logical intentions of genus, species and differentia. He

analyzes first intentions (formed from sensory experience) before second intentions (formed

from intellectual concepts). Then, he considers simple substances, followed by a chapter in

6 “ex compositis simplicium cognitionem accipere debemus et ex posterioribus in priora deuenire, ut a facilioribus incipientes conuenientior fiat disciplina”. Leon. 43.P :11-14.

19

which he presents a short summary of what came before, followed by special considerations

regarding simple substances: the real distinction between essence and existence and the

differentiation of simple substances based on their particular admixture of act and potency.

Lastly, he treats the accidents. So in addition to the ordering of the three tasks which he sets

himself, two ordering hierarchies have been used: substances before accidents and composed

substances before simple substances. The result is the following schematum, with the number

between parentheses representing the relevant chapter of the Editio Leonina:

(1) The meaning of “being” and “essence”;

(2) How essence is found in composite substances.

(3) How essences in composite substances relate to logical intentions.

(4) How essence is found in simple substances.

(5) The real distinction between essence and existence and the differentiation of simple

substances.

(6) How essence is found in accidents.

Reception of the treatise

As already noted above, with the exception of his Summa Theologiae, no other work of Saint

Thomas has been commented upon as frequently as the De ente et essentia. According to

Grabmann, this fact bears witness to the popularity of the treatise, although it must be noted

that most of these commentaries have been written by fellow Dominicans, and so this only

proves its popularity within the Dominican Order. However, the oldest commentary on the De

ente et essentia was written by Conrad of Prussia, probably before Thomas’s canonization in

1323, as he refers to Thomas as “brother”. Not much is known of Conrad of Prussia, but he

was probably a secular priest because there is no mention of him belonging to any monastic

order. Only one manuscript of this commentary is known to exist, although according to

Bobik this clearly is not the original, on account of numerous “uncorrected faulty readings”.

In 1974, Bobik published a transcription of this manuscript, including his comments, but

without a verbatim translation of the text.7

7 CONRADUS DE PRUSSIA, JOSEPH BOBIK, JAMES CORBETT (EDTS.), The Commentary of Conrad of Prussia on the De ente et essentia of St. Thomas Aquinas, The Hague 1974.

20

Later commentaries on the De ente et essentia refer to Thomas as “saint” and have therefore

been written after 1323. Fellow Dominican Armandus de Bellovisu composed a commentary

on the treatise between 1323 and 1328, in which he included discussions of various passages.

The fifteenth century would be the next fertile period for commentaries on the De ente et

essentia, with works by Gerardus de Monte, Joannes Versorius, Joannes de Glogovia and

Thomas de Vio Cardinal Cajetan. From the sixteenth to the nineteenth century, commentaries

in Latin were written by Petrus Crockaert (1510), Raphael Ripa (1598), Hieronymus

Contarenus (1606) and Michael de Maria (1886). The last Latin commentary, by the Jesuit

Charles Boyer, was published in 1933.

As early as the end of the nineteenth century, commentaries in languages other than Latin

begin to appear. In 1882, Joseph Cardinal Pecci presents a summary of the De ente et essentia

in Italian, along with a commentary by his own hand. Three translations with comments by

the translator appear in French: by Emile Bruneteau (1914), M.-D. Roland-Gosselin (1926)

and Catherine Capelle (1947). The Latin text presented by Roland-Gosselin is semi-critical,

based on fifteen manuscripts that were available to him in Paris. Until the publication of the

Latin text of the De ente et essentia of the Editio Leonina in 1976, which was the first real

critical edition, his text was used by many translators and commentators. Translations and

commentaries in German were published by Rudolf Allers (1953), Franz Beeretz (1987),

Horst Seidl (1988) and Dieter Knoch (2008). In 2010, a translation of the De ente et essentia

by Edith Stein was published, including facsimiles of a handwritten commentary. Two

translations with commentary were published in English: one by Armand Maurer (1949) and

one by Joseph Bobik (1965). Maurer’s commentary allows room for the historical context of

the De ente et essentia, Bobik comments exclusively on its content. In Dutch, only two

commentaries were published: the first one in 1941 in Flanders by A.M. van der

Mensbrugghen. This translation, entitled Over het wezen en de wezenheid, uses odd choices of

Dutch words to refer to technical terms in Latin, rendering it rather inaccessible to

contemporary readers. A more up to date translation was published in 1986 by B. Delfgaauw,

based on the (semi-)critical Latin texts of Roland-Gosselin and the Editio Leonina. This

publication, entitled Over het zijnde en het wezen, also includes much useful commentary on

the historical context in which the De ente et essentia was written.8

8 The commentaries and translations prior up to 1974 are listed in: JOSEPH BOBIK, JAMES CORBETT, The

Commentary of Conrad of Prussia on the De Ente et Essentia of St. Thomas Aquinas, The Hague 1974, 7-9.

21

Chapter 2: Avicennian influence on the De ente et essentia

In this chapter, we will take a look at the ways in which the influence of Avicenna on Thomas

becomes clear in the De ente et essentia. On some occasions, Thomas acknowledges the fact

that he is representing an opinion of Avicenna, whether on its own or to strengthen the

argument of himself or another philosopher. I will label these instances “explicit references”;

the first part of this chapter is dedicated to an inventory and short commentary on these

acknowledgements of Avicenna’s influence. However, in other passages of the De ente et

essentia, even though Thomas does not acknowledge it, the influence of Avicennian thought

has been proposed by scholars commenting on the text. Therefore, in the second part of this

chapter, I will look at the implicit influences proposed by Roland-Gosselin and the editors of

the Editio Leonina of the De ente et essentia; I will again present an inventory and a short

commentary. In the third part, I will review a treatise by Louis De Raeymaeker in which he

compares the ontologies of Avicenna and Thomas. The fourth part of this chapter is dedicated

to the development of the real distinction between essence and existence within the context of

the metaphysics of Avicenna, and to how Thomas adopts this philosophical doctrine. We will

see that there is a lot of common ground, and that Thomas was highly influenced by

Avicenna, but at the same time he added to the Persian philosopher’s work through an

innovative use of the Aristotelian relationship between act and potency. The chapter will be

concluded with a brief summary of the most important points.

Explicit references to Avicenna and his works

We will start by examining those instances in which Thomas thought it prudent to explicitly

refer to Avicenna and his works to construct or strengthen his argument. In total, there are

thirteen of these explicit references to be found in the De ente et essentia (cf. Table 1). In fact,

Avicenna is the most referenced author in the opusculum, with the exception of Aristotle.

However, the primacy of references to Aristotle should not come as a surprise to us, as the De

ente et essentia is basically a summary and partial commentary on parts of the Greek

philosopher’s Metaphysics. Avicenna is referenced more often than his fellow Arabian

philosopher Averroës, who is cited only nine times in the De ente et essentia. A notable

difference between the two Arabian philosophers is that Thomas always seems to agree with

Avicenna when he cites him, while Averroës is sometimes cited to present a counter

argument.1

1 For instance, Leon. 43.3:107-110.

However, both Arabian philosophers are cited more often than Boethius and

22

Avicebron, who are cited three and four times respectively. The sixth and final source that is

explicitly called upon in the De ente et essentia is the Liber de causis, which is cited three

times.

If we look at the explicit citations of Avicenna, we note that Thomas mentions the name of

the literary work to which he is referring in only six out of thirteen cases. In total, Avicenna’s

Metaphysica is referred to four times (nos. 1, 2, 7 and 12), while his De anima is mentioned

only two times (nos. 11 and 13), with both references being made to the beginning of the

work (first book, chapter one). If we take all explicit references to Avicenna into account, we

note the same skewed ratio: in ten out of thirteen explicit references, Avicenna’s Metaphysica

is used as a source, while reference is made to his De anima on only three occasions.

Furthermore, all references to De anima are made within the confines of the fifth chapter of

the De ente et essentia, in which Thomas discusses the composition of the intelligences. Of

the ten times that Thomas refers to Avicenna’s Metaphysica, eight times reference is made to

the fifth book of that literary work, the only two exceptions being references nos. 1 and 2.

This is quite understandable, as they occur not in the main narrative of the De ente et essentia,

but in the introduction in which the importance of the work is explained (no. 1), and in the

first chapter in which the different terms used to refer to essentia are listed (no. 2).

Considering the above, it would not seem to be an exaggeration to label the fifth book of the

Metaphysica as the main Avicennian influence on the De ente et essentia, with the first book

of his De anima as a remote and far less important second.

On several occasions, the reference to Avicenna does not introduce a new element to

Thomas’s argument; rather it strengthens a thought introduced by Thomas or others, and

therefore constitutes an appeal to authority. In two cases, Avicenna is referred to as agreeing

with other philosophers: once he is cited in agreement with Boethius and Averroës (no. 3),

and once in agreement solely with Averroës (no. 7). In both these cases, the keyword used in

the conjunctional clause is “etiam”. In other instances, Thomas uses a reference to Avicenna

as the natural outcome of his own argument. These references are all introduced by the

keywords “unde” (nos. 4, 5, 8 and 11), which is invariably translated by “whence”, and “ideo”

(nos. 6, 10 and 13), which is translated as “this is why”. The fourth and final keyword used by

Thomas to introduce a citation of Avicenna is “ut”, translated by Bobik with “as”. When this

keyword is used, a thought or principle of Avicenna is introduced which is new (nos. 1 and 2),

or which is cited in contrast to the preceding argument (nos. 9 and 12).

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The first explicit reference is worth commenting upon because it cites a general principle,

formulated by Avicenna, which is then combined by Thomas with a citation of Aristotle, in

order to accentuate the importance of the De ente et essentia. Considering that being and

essence (“ens et essentia”) are the first things conceived by the intellect, as Avicenna posits, it

is very important to understand these two concepts, as they constitute the fundament on which

all other philosophical and theological knowledge rests. The explicit mention of Avicenna in

this first sentence of the opusculum, in combination with a referral to Aristotle, could be

considered a clear indicator that the works and thought of Avicenna are going to represent a

major influence on the De ente et essentia.

However, it seems that Thomas severely misquotes Avicenna, as the Latin translation of his

Ilāhiyyāt reads “being and thing and necessity”.2 Robert Wisnovsky puts forward the thesis

that Avicenna introduced the Arabic word for essence (māhiyya), as a substitute for the

Arabic word for thing (shay’). This substitution occurred over time, while considering the

theological discussion on the distinction between things and existents, and had the abstract

noun “thingness” (shay’iyya) as an intermediary.3

Moreover, as Delfgaauw notes, being appears to be more intuitive as a first impression upon

the intellect than essence.

It is therefore possible that Thomas either

possessed a manuscript of the Latin translation of the Ilāhiyyāt of Avicenna in which the

translator used essentia instead of res, or Thomas might have substituted essentia for res

himself, having knowledge of Avicenna’s later work. Interestingly, the omission of necesse

implies a purely philosophical interest in Thomas, as necessity in the teachings of Avicenna

refers to necessary being, which is limited to the being of God, and to the origin of the world

through necessary emanation.

4

2 “ens et res et necesse”. M.-D. Roland-Gosselin o.p., Le De Ente et Essentia de s. Thomas D’Aquin, Kain 1926, 1 note 2.

But this is instantly explained by Delfgaauw: we should not

interpret Thomas here as positing that the understanding of an essence is a first impression

upon the intellect, but simply that being is instantly perceived as being in this or that manner.

A third complication regarding this explicit reference to Avicenna may occur in translating

the Latin word “ens”. Considering the lack of indefinite articles in Latin, this word may be

alternatively translated as “being” or as “a being”. The first possibility poses a problem as it

may be read as either an abstract noun or a gerund, and is therefore ambiguous. The

alternative seems to be synonymous to “thing” and should therefore be rejected; a thing

3 ROBERT WISNOVSKY, Avicenna’s Metaphysics in Context, London 2003, 145-180. 4 THOMAS VAN AQUINO, B. DELFGAAUW, Over het zijn en het wezen, Kampen 1986, 71-72 noot 4.

24

clearly refers to the composite of existence and essence, and should therefore not be used for

one of its principles.

The second explicit reference merits extra attention, not because of its content, but because of

the apparent uncertainty of its origin. Thomas refers to Avicenna to include the word “forma”

as another name for essentia in his list of synonyms in the first chapter of the De ente et

essentia. This is the only occasion in which Roland-Gosselin and the editors of the Editio

Leonina disagree on the place in the Metaphysica that is referred to. The Editio Leonina gives

two options: the sixth chapter of the first book or the second chapter of the second book.5

Since Thomas himself refers to the second book (“ut dicit Auicenna in II Metaphisice sue”),

the first option seems a bit puzzling, even more so because the word “forma” is not

encountered in the line cited from book 1, chapter 6 (“unaqueque res habet certitudinem

propriam que est eius quiditas”). To add to this enigma, Roland-Gosselin’s text, which is

based on eight Parisian manuscripts, reads “ut dicit Auicenna in tercio Methaphysice sue”. As

a possible source of this reference Roland-Gosselin proposes the fifth chapter of the third

book, but with caution.6 Roland-Gosselin’s critical apparatus notes no variations within the

eight Parisian manuscripts. However, the Editio Leonina notes five variations among its

sources, consisting of inversion of “Metaphisice” and “sue”, and different ways in which

“Metaphisice” is altered, but not one manuscript seems to refer to the third book of the

Metaphysica. Moreover, in their introduction, the editors of the Editio Leonina signal that

some of the earliest manuscripts gloss Avicenna’s Sufficientia, rather than his Metaphysica.

They evaluate this odd variation as an early misreading which was corrected at a very early

stage, because “the Sufficientia does not refer to forma in this sense”.7

5 Metaph. 1/6:72v a or Metaph. 2/2:76r a. See Leonina edition, book 43, page 369, note 36.

In conclusion, it would

appear that all manuscripts selected to be used by the editors of the Editio Leonina refer to the

second book of the Metaphysica, while all manuscripts which were used by Roland-Gosselin

refer to the third book. In addition, the exact place that is referred to by Thomas is uncertain,

both for Roland-Gosselin as for the editors of the Editio Leonina. That this reference to

Avicenna poses a problem also becomes evident from the commentary on the De ente et

essentia by Thomas (cardinal) Cajetan. Although the 1907 Roman printing of the Latin text

glosses “sicut dicit Avicenna in II Metaphysicae suae”, Kendzierski and Wade seem fit to

6 Metaph. 3/5:80 b. See M.-D. Roland-Gosselin o.p., idem, 4:2-3 and note 1. 7 “la Sufficientia ne touche pas ce sens de forma”. Leon. 43.350 :c.5, p25.

25

translate “as Avicenna says in III Metaphysicae” while referring to the fifth chapter of the

third book, their translation being based upon the 1934 printing by Marietti.8

At this point, it should be noted that Roland-Gosselin draws attention to the fact that the Latin

translation of the Ilāhiyyāt often uses the word “certitudo” where the Arabic word for essence

appears in the original text.

9 Taking into account all of the above, and the fact that Roland-

Gosselin’s text antedates the Editio Leonina of the De ente et essentia, the following solution

to the described enigma seems highly plausible: the text should read “II Metaphisice” and

refers to Metaph. 2/2:76r a “hec certitudo… est forma”, as suggested by the Editio Leonina.

The text variation of the Parisian manuscripts could be explained by a common original,

whether included in those eight or lost, in which the text was altered by mistake (creating a

corruption) or even on purpose by a scribe who thought he was correcting an error made by a

previous copier of the manuscript. The alternative source for the reference quoted by the

Editio Leonina (Metaph. 1/6:72v a) might be taken from Roland-Gosselin, who presents it as

an example of the use of the word “certitudo” by the translator of the Arabic original of the

Metaphysica, rather than a possible source of the explicit reference made to Avicenna by

Thomas. The seemingly incorrect translation of the work of Cajetan can also be explained by

a contrast between Italian and Parisian versions: in a footnote on the very first page of their

translation, Kendzierski and Wade remark that they have used two Latin texts. One prepared

in Turin by Laurent and printed by Marietti in 1934, and one prepared in Paris in 1883.10

Implicit references to Avicennian thought

This

seems to corroborate the thesis that the Parisian versions refer to the third book, while Italian

versions cite the second book.

In addition to the abovementioned cases in which Thomas himself felt it opportune to mention

the author of the incorporated influences on his opusculum, there are quite a few instances in

which commentators on the De ente et essentia have noticed a striking similarity with parts of

Avicenna’s work, where Thomas does not reference his sources. An inventory of these

implicit references is presented in Table 2.

8 S. THOMAE AQUINATIS, Opusculum De Ente et Essentia: Commentariis Caietani Illustratum, Romae 1907, 30. CAJETAN, LOTTIE KENDZIERSKI, FRANCIS WADE, Commentary on Being and Essence, Milwaukee 1964, 72. 9 Also in note 1, ibidem, 4. 10 CAJETAN, LOTTIE KENDZIERSKI, FRANCIS WADE, Commentary on Being and Essence, Milwaukee 1964, 39 note 1.

26

Three implicit references are included in Table 2 without specifying an Avicennian work as a

source. All three of these are taken from the notes of Roland-Gosselin. In no. 2 Thomas notes

that the opinion which he rallies against is that of Averroës, and that Thomas agrees with the

alternative opinion, as he himself wrote in his commentary on the Aristotelian Metaphysics11

Three longer tracks of text which betray Avicennian influence deserve more attention. The

editors of the Editio Leonina note that lines 105-150 of chapter 2 are comparable to Thomas’s

commentary on the Libri quattuor sententiarum of Peter Lombard, and that in that work

reference is made to Avicenna (no. 5).

.

In no. 3, Roland-Gosselin notes that the technical term “materia signata” entered the

scholastic vocabulary because the translator of Avicennian works used it. In contrast, the

translator of the works of Averroës used the term “materia demonstrata” for the same gloss;

no specific literary source is mentioned. In no. 7, Roland-Gosselin remarks upon Avicenna’s

multiple attacks on the Platonic notion of separate forms. In this instance, reference to

Avicennian sources is given (Metaph. 5/1:87r b E, Metaph. 7/2:96r and Metaph. 7/3:96v) but

these are not included in the table as their relevance to the citation from the De ente et

essentia is not self-evident.

12 Also, a direct reference to Avicenna is incorporated

in the critical apparatus.13 Most interestingly, Roland-Gosselin has not noticed this

Avicennian influence on Thomas. Another major passage of the De ente et essentia is thought

to be of Avicennian origin by the editors of the Editio Leonina: lines 195-222 of chapter 2.14

A third large portion of the opusculum which might be of Avicennian origin is lines 26-155 of

chapter 3, making up most of that particular chapter.15

In conclusion, it can be said that the list of implicit references to Avicennian sources includes

a wider variety of literary works than that of the explicit references presented in Table 1. In

addition to the Metaphysica and the De Anima, Thomas’s implicit references also include

Avicenna’s Logica and the Sufficientia. Two sources are notable for their frequency: the fifth

book of the Metaphysica and the first book of the Logica, occurring three and four times

respectively.

This is a reference to Avicenna’s

threefold consideration of essences, as described in the section summarizing the comparative

study by De Raeymaeker below.

11 In Met. L. VII, l. 9 (t. 25, p. 3 b). 12 Super Sent. I d. 25 q. 1 a. 1 ad 2, referens Avicennam. Leon. 43.371:note on 105-150. 13 Metaph. 5/3:88r a A. 14 Metaph. 5/5:89v D-E. 15 Metaph. 5/1-2:86v a-87v b.

27

Avicennian influence on the De ente et essentia: De Raeymaeker

A third mode of influence is neither marked by Thomas himself, nor by the compilers of

(semi)critical editions of the text of the De ente et essentia. In contrast, it is remarked upon in

handbooks and articles on Thomist metaphysics. To give a broad indication of the extent to

which Avicennian thought is regarded as highly influential on the works of Thomas in

general, and on his De ente et essentia in particular, I will briefly review a short treatise

precisely on this topic written by Louis De Raeymaeker, as it focuses most specifically at the

topic at hand.16

He starts by noting Avicenna’s accent on the priority of three concepts: being, thing and

necessity. These concepts are prior in that they constitute the first experience of the intellect

and because one is not able to explain them in simpler or prior concepts. Existential

knowledge is always a mixture of the experience of existence which is mediated or “troubled”

by quiddity: both sensory and mental experiences refer to being-in-this-or-that-manner.

However, since Avicenna contents that existence is not included in any essence, they must in

one way or the other, be separate. De Raeymaeker sets out to clarify their distinction within

the Avicennian corpus. First, he summarizes Avicenna’s understanding of quiddity or

essence. An essence can be considered in three ways: absolute (in se), extramental (in re) or

mental (in intellectu). Regarding these last two, it is posited that individuality characterizes an

essence in re, while universality characterizes an essence in intellectu. De Raeymaeker

comments on the similarity to the Elementatio theologica of Proclus and the Liber the causis,

attributed by the Arabian philosophers to Aristotle, in which a threefold causal hierarchy was

described: (1) absolute perfection, (2) universal perfection and (3) individual things. That

Avicenna was influenced by the Neo-Platonic tradition is almost a matter of certainty.

However, Avicenna rejects the Platonic notion of individual participation in an otherworldly

idea; his teaching on essences is constructed in an Aristotelian fashion.

Most importantly, according to De Raeymaeker, Avicenna considers existence to be

superadded to the essence, labeling existence as mere accident (‘arad). However, this does

not denote one of the nine categories of accidents as described in Aristotle’s ten genera.

Rather, Avicenna calls existence concomitant to essences (“concomitans” in the Latin

translation of the Ilāhiyyāt), denoting a collateral or ancillary relation. These concomitant

16 LOUIS DE RAEYMAEKER, Vergelijkende studie over de betekenis van het “zijn” in de metafysiek van Avicenna en die van Thomas van Aquino, Brussel 1955.

28

properties either belong to the essence on account of itself (De Raeymaeker poses the

property of unevenness which belongs to the number three on account of its own essence), or

on account of some extrinsic principle, as is the case with existence, since it is caused by an

act of creation by God. The external causation of existence is necessitated by the fact that

existence permeates the ten genera, since it is found in all its categories. Therefore, the cause

of existence of all essences should be sought outside the categories. This also explains why

we can understand the nature of a being (a djinni for example) without knowing if such a

being actually exists in reality, since its existence is not included in its essence. But even

though it comes from without, existence still belongs to the essence as an attribute. Essences

therefore seem prior in Avicenna’s ontology. De Raeymaeker succinctly summarizes

Avicenna’s stance by stating that in his ontology “existence is a derivative of the totality of

quidditative principles”.17

Avicenna also claims that an essence which has non-being as a concomitant attribute

(something which does not exist in reality), still sustains itself in an absolute sense, on

account of its inner quidditative structure, independent of any relationship to external reality,

including existence. An essence considered absolutely (in se), possesses an “inner firmness”

and presents itself as such to our intellect.

18 We may then conclude that for Avicenna both

existence and non-being present itself as concomitant properties of essences; but while

existence comes from without, having its cause in God who transcends the ten genera, it is

supported by non-being, in which “the inner firmness inherent to the essence absolutely

considered is directly and necessarily expressed”.19

De Raeymaeker then comments on Thomas’s reception of Avicennian thought. He notes that

especially Thomas’s earlier works (such as the De ente et essentia) show a profound influence

Existence does not exhibit the

independence of quiddities. On the contrary, existence is always related to an essence, and

cannot be considered absolute. Existence therefore only has relative value, while essences

have absolute value. From the above, De Raeymaeker concludes that for Avicenna,

ontological priority lies with quiddities or essences, which he states is understandable given

the influence of Neo-Platonic sources on his philosophy. Given the emphasis on the absolute

quality of essences, Avicenna’s ontology may rightly be called “essentialism”.

17 “zo is het bestaan een derivaat van het geheel aan quidditatieve principes”. Ibidem, 11. 18 “de loutere quidditeit, d.i. de niet-zijnde quidditeit, de quidditeit waarvan het niet-zijn een eigenschap is, bezit een inwendige stevigheid en dringt zich als zodanig op aan ons verstand”. Ibidem, 11. 19 “waarin de inwendige stevigheid eigen aan de op zichzelf (absolute) beschouwde quidditeit rechtstreeks en noodzakelijk tot uitdrukking komt”. Ibidem, 11.

29

by Avicenna. Thomas too posits the priority of being in relation to the human intellect, which

is characterized by a fundamental and a priori receptivity toward being, which in fact

constitutes its formal object. The human intellect fulfills its essential goal, and arrives at

reflexive knowledge of itself, when its openness toward being is met by the sensory

experience of individual existents. This goes against Platonic thought and several mental

experiments proposed by Avicenna, in which the human mind experiences itself in an

exploration of the inner world.

The threefold division of essences (in re, in se, in intellectu) can also be found in Thomas’s

works, for example in this excerpt from chapter 4 of the De ente et essentia: “Now, a nature

or essence signified as a whole can be considered in two ways. In one way it can be

considered according to its proper content, and this is an absolute consideration of it […] In

the other way, an essence is considered according to the existence it has in this or that […]

This nature has a twofold existence, one in singular things, the other in the soul”.20

The real distinction between essence and existence

Taking

into account that with “soul” (anima) Thomas here refers to the human intellect, the

Avicennian influence becomes evident. As noted above, this entire passage of the De ente et

essentia has been linked by Roland-Gosselin to the first two chapters of the fifth book of

Avicenna’s Metaphysica.

With regard to Thomas’s argument for the distinction between esse and essentia, the influence

of Avicenna’s thought is unmistakable, to the point where De Raeymaeker claims that the

evidence that Thomas gives for the distinction is actually identical to that given by Avicenna:

“Whatever is not of the understood content of an essence or quiddity is something that comes

from without and makes a composition with the essence […] it is clear, therefore, that

existence is other than essence or quiddity”.21

20 “Natura autem vel essentia sic accepta potest dupliciter considerari : uno modo secundum rationem propriam et haec est absoluta consideratio ipsius […] Alio modo consideratur secundum esse quod habet in hoc vel in illo […] Haec autem natura duplex habet esse : unum in singularibus, aliud in anima”. Leon. 43.3:26-29, 45-47, 52-53.

So, although Thomas acknowledges the

distinction between existence and essence and the external causation of existence on account

of its independence of the essence’s content, he still posits a strong relationship between the

two principles of being, as they form a composition with each other. In accord with Avicenna,

21 “Quidquid enim non est de intellectu essentiae vel quidditatis, hoc est adveniens extra et faciens compositionem cum essentia […] Ergo patet quod esse est aliud ab essentia vel quidditate”. Leon. 43.4:94-95, 102-103.

30

he sees existence as a concomitant property of essences, which is added to it by an external

cause, which he claims to be God.

Let us now depart from the comparative study by De Raeymaeker to take a closer look at the

real distinction between essence and existence, as proposed by Avicenna. Assuredly, it did not

develop within an intellectual vacuum. In fact, the discussions among the different factions of

mutakallimūn (Islamic theologians) on the relationship between the concepts of “thing”

(shay’) and “existent” (mawjūd), appear to have provided Avicenna with the necessary

impetus to develop his thought. Moreover, the discussion on things and existents did not

merely arise out of philosophical interest in ontology, but rather from a theological interest to

resolve apparent paradoxes which presented itself in the interpretation of various verses of the

Qur’ān. The mutakallimūn were faced by two distinct problems: one the one hand, they

sought to resolve the question whether or not it could be said that God is a thing. On the other

hand, they were trying to make sense of the Qur’ānic verses in which the creative power of

God was exalted, for example sura 36:82: “Verily His command, when He intends a thing, is

only that He says to it, ‘Be!,’ and it is”. What is this thing, the object of God’s command to

be, that is before it exists? How was this description of divine creative power to be reconciled

with Neo-Platonized Aristotelian ontology, of which the Islamic dogmatists were the

intellectual heirs? It was within the context of these theologically driven debates that the

conceived relationship between things and existents gave rise to the Avicennian distinction

between essence and existence.

We find Avicenna’s approach of the subject matter in his Kitāb ash-Shifā’, and more

specifically in chapter 5 of the first book of the Ilāhiyyāt. Here, Avicenna makes three

important points: first, that “thing” and “existent” signify primitive, basic, and immediately

apprehensible concepts. As such, they cannot be put in a genus. Second, he emphasizes that

there is a clear difference in meaning between shay’ and mawjūd: shay’ refers to an entity

with regards to its essence, while mawjūd refers to an entity with regard to its existence.

Third, he affirms that thing and existent are co-implied (mutalāzimāni), and by inference, that

neither term is logically prior to the other.

The development of the concept of mawjūd (existent) into wujūd (existence) seems obvious,

but some explanation is required to follow the conceptual development of māhiyya (essence,

literally “whatness”) from the concept shay’ (thing). A possible explanation is offered by a

careful reconstruction of an argument in the Ilāhiyyāt, in which Avicenna shows in what sense

31

thing and existent differ from each other. He does this by differentiating between specific

existence (al-wujūd al-khāṣṣ) and affirmative existence (al-wujūd al-ithbātī). Predications of

specific existence assert what something is, and is also called “inner reality” (haqīqa, which

would later be translated into Latin as certitudo). It is called specific because it denotes

existence in a class (species) of things. On the other hand, predications of affirmative

existence assert that something is. Since inner reality and specific existence are identical,

argues Wisnovsky, and inner reality is also identical to māhiyya, it follows that specific

existence is identical to māhiyya. The three concepts of specific existence, inner reality and

whatness/essence are therefore intensionally identical. And since affirmative existence is

distinct from specific existence, it follows that existence is distinct from essence.

According to Wisnovsky, there exists the possibility that the development of māhiyya from

shay’ was facilitated by Avicenna’s use of the word shay’iyya (“thingness”). In another

passage from the Ilāhiyyāt (38:20-23), he fulminates against people who defend the viewpoint

that among all that is predicated, there are non-existent entities which have no “thingness”. He

boldly advises these people to “go back to whatever dogmatic formulae they babbled out

unintelligibly”. As an aside, the entities that are referred to here are impossible entities, the

third category of the triad necessary-contingent-impossible existence. The hypothesis that

shay’iyya served as a bridge between the concepts of shay’ and māhiyya faces two challenges:

first, we would suspect broad usage of the term in the ninth and tenth century debates between

mutakallimūn; and this is simply not the case. Despite the fact that only a fraction of kalām

texts from that time period is available to modern scholars, there seems to be no indication

that the term was widely used. There exists the distinct possibility that al-Maturidi is the

original inventor of the term shay’iyya. This claim is even more credible given the fact that

Avicenna grew up in the area outside Bukhara, where the influence of the Samarqandi

Hanafism of al-Maturidi (a school of Islamic jurisprudence) was strongly felt. It appears to be

a likely scenario that Avicenna encountered the term shay’iyya sometime during his early

education. Naturally, it is also quite possible that Avicenna himself came up with the word

shay’iyya; it is a straightforward abstract noun, constructed through use of the suffix “-iyya”,

similar to the English suffix “-ness”, which serves a similar purpose. In his works, Avicenna

showed a predilection to invent and use new abstract nouns.

However, Thomas was not merely influenced by the intellectual heritage of Avicenna; he

would also significantly add to it. After his treatment of the argument for the real distinction

between esse and essentia in all substances but God, he continues: “It is necessary therefore

32

that the quiddity itself or the form, which is the intelligence, be in potency with respect to the

existence which it received from God; and this existence is received as an act. It is in this way

that potency and act are found in the intelligences”.22 Thomas here applies the Aristotelian

notion of potency and act with regard to movement, to the metaphysical relationship between

existence and essence, with positive result. However, this also implies a radical opposition to

the idea that essences are somehow prior to existence, and in fact, to the notion of

essentialism. For following Aristotle, Thomas cannot but grant priority to act. Not only

because Aristotelian philosophy declares that actuality holds priority over potency, but also

because potency can only be thought of in relationship to a corresponding act. I am therefore

of the opinion that Thomas’s ontology could be considered existentialist, rather than

essentialist like that of Avicenna. As Thomas would later formulate in the De potentia,

existence is the “act of acts” and the “perfection of perfections”.23

Conclusion

In this chapter we have seen four different aspects of Avicennian influence on the De ente et

essentia. In the first part we looked at those instances where Thomas explicitly attributes a

thought or argument to Avicenna. We have seen that Avicenna is the most cited philosopher

in the opusculum (once again, with the exception of Aristotle) and that Thomas always cites

him while in agreement with his philosophy. We have noted how on one occasion, the source

of the cited reference is uncertain on account of a corruption of the text. We have also seen

that the most often cited source of Avicennian references is the fifth book of his Metaphysica.

In the second part we looked at passages where the editors of (semi-)critical editions of the

text of the De ente et essentia have noted a specific Avicennian influence on the argument

being put forth by Thomas. In addition to a number of small references, we saw that three

longer tracts of text were signaled to have originated with Avicenna. The first two of these

can be found in chapter 2 of the De ente et essentia, both of them being highly influenced by

the fifth book of Avicenna’s Metaphysica. While the first two passages were noted upon by

the editors of the Editio Leonina of the text, the third passage, which is supposedly of

Avicennian origin, is commented upon by Roland-Gosselin (and De Raeymaeker). This tract

of text too refers to the fifth book of Avicenna’s Metaphysica and makes up the evidence for 22 “Ergo opportet quod ipsa quidditatis vel forma quiae est intelligentia sit in potentia respectu esse quod a Deo recipit ; et illud esse receptum est per modum actus”. Leon. 43.4:149-152. 23 “Quaelibet autem forma signata non intelligitur in actu nisi per hoc quod esse ponitur […] Unde patet quod hoc quod dico esse est actualitas omnium actuum, et propter hoc est perfectio omnium perfectionum”. De potentia, q. 7, a. 2, ad 9.

33

the real distinction between existence and essence, one of the most important arguments of the

entire text.

In the third part, we looked at a small treatise by De Raeymaeker in which he discusses

Avicennian influence of Thomas’s ontological thought. We saw that at least three major

principles are of definite Avicennian origin: the notion that essences can be considered in a

threefold manner (in se, in re and in intellectu), the idea that existence must have a cause

which is external to the essence (at the same time being proof for the distinction between

existence and essence), and the notion that God is this external cause of existence since God

transcends the ten genera.

In the last part, we looked at the origin of this distinction between essence and existence in

discussions of Islamic theology in the ninth and tenth century, and a possible explanation of

the evolution of the Arabic word for essence (māhiyya) from the word for thing (shay’). In

addition, we noted that Thomas goes beyond Avicenna’s influence on his own philosophy

when he makes innovative use of the principles of act and potency by applying them to the

relationship between existence and essence. We concluded that although Avicennian

influence on Thomas is undeniable, they still represent opposing views of the relationship

between the principles of being: Avicenna giving priority to essences on account on their

“inner firmness” when absolutely considered, while Thomas confers priority to existence

because it is related to essence as act is to potency, and of those two, act is ultimately prior.

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Chapter 3: The content of the De ente et essentia

This third chapter constitutes an attempt to give a brief but adequate summary of the contents

of the De ente et essentia, which special attention for Avicennian influences where warranted.

The structure of this summary will be topical, rather than strictly following the outline of

Thomas’s opusculum. Moreover, essences considered in re will be dealt with prior to, and

more in depth than, essences considered in intellectu, thereby giving priority to ontological

notions over notions of logic and epistemology. This means that the discussion of first and

second intentions will only be briefly covered at the end of this chapter. In addition, the topic

of essences as found in accidents will also be minimally covered, since essences are found in

accidents in a less perfect sense than in substances. Therefore, the topics focused on in this

chapter will be the way in which essences are found in substances, with a slight emphasis on

simple substances, because of the amount of attention that the argument on the real distinction

between esse and essentia has garnered from contemporary philosophers.

On the different meanings of the words ens and essentia

As mentioned above, the actual treatise of the De ente et essentia starts with a discussion of

the different meanings of the words “ens” and “essentia”, thereby fulfilling the first task

which Thomas has set himself. Applying his general principle that we should start with

examining the composed to acquire knowledge of the simple, Thomas first has a look at ens.

This implies that he considers ens to be posterior to essentia. Following Aristotle, Thomas

posits that ens can be understood in two ways: first as referring to real substances which can

be divided into the ten genera or categories, and second as pointing at anything which can be

included in a positive affirmation, which includes negations and privations. However, the

word essentia is only properly used in relation to the first understanding of ens (in fact, he

remarks that privations are an example of things that do not possess an essence).

The word “essentia” then refers, he continues, to the principle according to which extramental

existents are subdivided into the different genera, and thus, it points at something which these

existents have in common. This principle can also be called quiddity (quidditas), as it refers to

the definition according to which an existent is put into its genus or species, form (forma),

following Avicenna’s reference to an existent’s full determination, or nature (natura),

following reference to the way in which an existent can be understood by the intellect,

according to Boethius. Thomas concludes this section by remarking that the word “essentia”

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proper refers to the fact that it is a principle through and in which an existent has existence.1

As noted in chapter 2, this constitutes an implicit reference to Avicenna’s Logica, with

comparable phrases noted in his Metaphysica and his Sufficientia.2

How essentia is found in diverse beings

The etymological claim

that Thomas repeats here is that the word “essentia” thus denotes the mode of being (modus

essendi) of an existent. To this list of words that may denote essentia (quiddity, nature and

form) we should add the word “certitudo”: this is the Latin translation of the Arabic word

“haqīqa”, which Avicenna uses to refer to essence when emphasizing its inner firmness,

which establishes certitude or permanence in substances.

After the discussion of the various meanings of ens and essentia, Thomas comes to the major

part of his treatise: the way in which essences are found in different beings. He orders his

argument in the following way: since the word essentia is absolutely and with priority used in

substances, and only with qualification and posterior in accidents, he will focus on substances

first. And because in simple substances essentia is “more hidden from us”, he will start with

composed substances, following the principle that one should progress from easier to more

difficult subjects.3

How essentia is found in composed substances

The structure that Thomas utilizes in his De ente et essentia is a very

logical one: since the composed substances include matter in their essence, they are sensible,

and therefore more intuitively explained and understood than simple substances that exclude

any material component. Therefore, Thomas may build his argument using examples from

experience, which is than abstracted to deal with separate substances. The same order will be

followed in this exposition of de content of the De ente et essentia.

With regard to composed substances, Thomas remarks that they are made up of matter as well

as form, and that essentia is not to be likened to either one of those, to anything added to them

from without, or to the relationship between them. Essentia therefore signifies the composite

of matter and form, which is affirmed by Boethius, Avicenna and Averroes (this is one of the

occasions where an explicit reference of Avicenna is used for authority, as noted in chapter 2).

But Thomas has to clarify this identification of essentia with the composite of matter and

form, because of the notion that matter is the principle of individuation, while an existent’s

1 “Sed essentia dicitur secundum quod per eam et in ea ens habet esse”. Leon. 43.1:50-52. 2 M.-D. ROLAND-GOSSELIN, Le De ente et essentia de S. Thomas d’Aquin : texte etabli d’apres les manuscrits parisiens, Paris 1948, 4, n. 4. 3 “Sed quia illarum substantiarum essentie sunt nobis magis occulte […]”. Leon. 43.1:64-65.

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essence signifies its definition which puts it into a genus. The latter would imply that all

existents in a particular genus share the same essence, but this universality of the essence

would counteract the individuating force of the included matter. This apparent paradox is

clarified by distinguishing between designated and non-designated matter. Designated matter

(materia signata) is matter which is considered under determined dimensions. In other words,

it can be pointed at; it is either this matter, or that matter, rather than matter in general.

Designated matter is the principle of individuation, while non-designated matter is included in

a composed substance’s definition. Thomas uses the example of a man to elucidate his point:

the definition of man includes a body of bone and flesh (non-designated matter), but a

particular man is individuated by his particular body, the bones and flesh that we can point at

(designated matter). The technical term materia signata finds its origin in the Latin translation

of Avicennian works.

How essentia is found in simple substances

Thomas now arrives at arguably the most controversial part of his treatise on essence and

existence: how essence is found in simple substances. The substances which do not include

matter in their essence can be divided into three categories: the human soul, intelligences (the

angels of the Jewish-Christian tradition) and God, which Thomas here refers to as the First

Cause. He first defends the position that the simple substances do not include matter in their

essence, against the viewpoint of other philosophers, among them the Franciscan friar

Bonaventura, his colleague at the University of Paris. These philosophers propose, following

the Fons vitae of Avicebron, that the human soul and the intelligences include incorporeal

matter in their essence, which allows them to be individuated and differentiated from God.

Thomas argues against this viewpoint that only substances which are separated from matter,

whether corporeal or incorporeal matter, can be regarded as intelligent or intelligible, because

intelligibility is linked to immateriality. Therefore, God, the angels and the human soul cannot

include matter in their essence, on account of their power of understanding.

So, in simple or separated substances, essence is identical to form, quiddity or nature. The

absence of matter is possible since within composite substances, form is the cause of the

existence of matter, and causes may exist independently of their effects, but not vice versa. It

is therefore quite possible for forms to exist without matter, but not for matter to exist without

form. The identification of formless matter with prime matter (prima materia) is therefore

purely conceptual and does not refer to an actual existent. That composed substances include

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matter in their essence is due to their distance from the “First Principle”, which is yet another

way to refer to God (later we will see that this is due to the correlation between a substance’s

distance from God in the Neo-Platonic scheme of emanation, and the amount of potentiality it

exhibits).

Thomas goes on to state two major differences between composed and simple substances.

First, he notes that while the essence of a composed substance can be signified as either a

whole or as a part, the essence of a simple substance can only be signified as a whole, as it

consists of nothing but form. Since designated matter is the individuating principle, a person

is not identical to humanity, but to humanity as individuated by a particular body, or more

specifically, this flesh and these bones. But simple substances, in which matter is not

included, cannot be individuated. Therefore, what is signified by the essence is the simple

substance itself. The second difference is related to the first: because of the absence of matter

in the essences of simple substances, and the subsequent impossibility of individuation, there

can only be one individual per species. In other words: no two simple substances include

identical essences, each individual is a species unto itself.

On the difference between God and the other separated substances

The following part of the discourse will be examined more in depth, because it constitutes a

matter of some controversy. As Scott MacDonald points out, two objections may be leveled at

Thomas’s assertion that the human soul and the intelligences are simple substances. The first

objection is that this would mean that the human soul and the intelligences are like God

(which is objectionable on principle). The second objection is that human souls cannot be

individuated, because they do not include matter in their essences.4

If Thomas wants to refute the first objection, he would have to prove that human souls and

intelligences are, in some way or another, not like God. He does so by pointing out that in

separate substances apart from God, there resides an admixture of potentiality and actuality,

while God is Pure Act. The potentiality found within the separate substances other than God

is a result of the specific relationship of essence and existence in these beings. It is precisely

in this exposition of the difference between God on the one hand, and the angels and human

souls on the other hand, that the real distinction between essence and existence plays its

highly influential role.

4 SCOTT MACDONALD, ‘The Esse/Essentia Argument in Aquinas's De ente et essentia’, in: Journal of the History of Philosophy, Volume 22, Number 2, 157-172,158.

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The real distinction between esse and essentia in substances other than God

The Avicennian origin of the real distinction between essence and existences has already been

examined in chapter 2. In this chapter, we will take a look at the description of the distinction

within the confines of the De ente et essentia. Thomas begins his argument by stating that

“everything that does not belong to the concept of an essence or quiddity comes to it from

outside and enters into composition with the essence”. According to MacDonald, this basic

premise has to be slightly rephrased to include the possibility of identification of essence and

existence. His general principle for the argumentation then becomes: “Whatever belongs to a

thing and is not part of its essence either comes from without and effects a composition with

the essence or itself constitutes the entire essence”.5 Thus three possible relationships between

essence and existence are listed: first, existence as part of the essence, second, existence

coming from without and effecting a composition with the essence, and third, existence

constituting the whole of the essence. Thomas first disproves the first possible relationship

between existence and essence by stating that one cannot understand an essence without

understanding its parts.6 Therefore, if existence truly constitutes a part of the essence of a

substance, knowing whether or not a substance actually exists would flow naturally from

knowing what a substance is. However, one can know what a phoenix is without knowing if it

actually exists in reality.7

However, something is inherently flawed about the phoenix argument that Thomas presents

here. It only seems to be a valid argument when we accept the essentialist view of ontology

which Thomas sets out to refute. It appears to be important to know if Thomas beliefs that

phoenixes exist in reality, but this does not become clear from the text of the De ente et

essentia. If it is true that Thomas follows Aristotle in claiming that only concrete individuals

exist, and that the Platonic Ideas, or pre-existent essences do not exist, then how can he talk

about understanding the essence of a phoenix? Unless he beliefs that at least one concrete

phoenix exists (or has existed) in reality, there simply is no essence to understand, let alone its

parts. But it seems that he discusses the phoenix precisely because whether or not it exists is

unknown (even to Thomas). Moreover, if we know what a phoenix is, this only means that

there exists some logical essence to be understood by our intellect, but this does not mean that

Hence, existence cannot be part of an essence.

5 SCOTT MACDONALD, ‘The Esse/Essentia Argument in Aquinas's De ente et essentia’, in: Journal of the History of Philosophy, Volume 22, Number 2, 157-172, 158. 6 “quia nulla essentia sine hiis que sunt partes essentie intellegi potest”. Leon 43.4:96-97. 7 “possum enim intelligere quid est (homo vel) fenix et tamen ignorare an esse habeat in rerum natura”. Leon. 43.4:100-101.

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there exist at least one concrete individual of the species in reality. This would mean that

Avicenna’s distinction can only be called “logical”, but not “real”. This might be the reason

that in his later works, Thomas distances himself from the phoenix argument. However, the

important point here is that knowledge of the existence of a being does not flow naturally

from the understanding of its essence. This means that for all beings, with the exclusive

exception of God, existence in reality is accidental to its essence; apart from God, nothing

exists necessarily.

Thomas continues by discussing the third possible relationship of essence and existence,

namely that of identification. He posits that it is a valid possibility, but that it can be

instantiated only once, because pluralization occurs in one of three ways, all of which are not

applicable to a substance in which essence and existence are identical. The first way is by

addition of some differentia, but nothing can be added to existence if it constitutes the whole

of the essence. The second way is by being received in different matters, but this would

constitute material existence, rather than absolute existence, and is therefore also impossible.

The third way of pluralizing is by the distinction between being absolute and being received

in something. The example that Thomas gives is that of separated heat as distinct from heat

received in something.8 This separated heat should be understood as heat considered in se,

more like a Platonic idea of heat than something which exists in reality. At first it may seem

strange that Thomas does not disprove this third possible way of pluralization. Some

commentators suggest that Thomas omits a refutation of this manner of pluralization because

its impossibility is obvious. MacDonald argues that the omission of a refutation is a deliberate

strategy of Thomas.9

Now, the existence of substances other than God must be caused by their own essence, or by

some extrinsic principle. Since nothing can cause its own existence (not even God, who has

no cause), the existence of substances other than God must be caused by something other than

The third way is not refuted because it is precisely the way in which

Creator and created beings differ from each other. God’s existence is absolute (ipsum esse

tantum), while the existence of creatures is received in their essence: it comes from without.

Therefore, in created beings, existence is other than essence, form, nature or quiddity. With

this intellectual step forward, Thomas has arrived at the real distinction between essence and

existence.

8 “sicut si esset quidam calor separatus esset alius a calore non separato ex ipsa sua separatione”. Leon. 43.4 :111-113. 9 SCOTT MACDONALD, ‘The Esse/Essentia Argument in Aquinas's De ente et essentia’, in: Journal of the History of Philosophy, Volume 22, Number 2, 157-172, 163.

40

themselves. But due to the impossibility of infinite regress (at least in medieval minds), at

some point there has to exist a First Cause, whose existence is not externally caused, but

wholly identical to its essence. This First Cause, or First Being, is God. Note that in this

particular part of the narrative, Thomas appears to have offered a proof for the existence of

God by means of causation, and a proof of the principle of monotheism, both appearing

almost as corollaries of the main argument.

Here Thomas returns to his task of proving that in separate substances other than God, there

exists an admixture of potentiality and actuality. With the argument for the real distinction of

essence and existence firmly in place, strengthened by the argument which identifies God as

the First Cause, this is now but a small step for the intellect. Thomas states that anything

which receives something from without is in potency with regard to what it receives, and what

is received into it is its act. Therefore, an angel, which is identical to its quiddity, is in potency

with regard to its existence, which it receives from God, and which it receives as an act.

What follows is a hierarchy of intelligent substances. The admixture of potentiality and

actuality in intelligent substances allows for their pluralization, since they differ according to

their ratio of potency and actuality. This is characterized as distance from the First Cause or

God within the scheme of emanation, so that the intelligent substance in which the potency-

actuality ratio is smallest is closest to God, and the one in which the ratio is the greatest is the

furthest removed from God. He goes on to posit that the angels are closer to the First Cause

(with various degrees of actuality), and that the human soul is, among the intelligent

substances, the furthest removed from God, and therefore exhibits the greatest amount of

potentiality. Due to this, the human soul actually attracts a corporeal substance with which it

shares its existence, resulting in a composite substance. The composite substances exhibit

even more potentiality, and thus cannot exist without matter. These substances are also

ordered hierarchically, with animals on top and the elements (water, fire, et cetera) on the

absolute bottom of the ladder.

The three ways in which essences are found in substances

The following part of Thomas’s treatise seems to summarize the preceding part in which the

real distinction between esse and essentia is presented, and in which the relationship between

God as First Cause and created beings is discussed. However, Thomas does add to his resume

a number of important implications for theological discourse. After his statement, that the

following part of the treatise will be structured along the lines of a threefold division

41

(invenitur enim triplex modus habendi essentiam in substantiis), Thomas begins with God, the

only substance in which its existence is its essence.10

The second way in which essences are found in substances, is in the way of created

intellectual substances, in which its essence and existence are distinct, and its essence consists

only of form without matter. To this category belong the angels and human souls. Their

existence is received rather than absolute, and therefore limited by its receiving nature.

However, the essences of these substances is unlimited, because they are not received into

matter. Thomas refers to the Liber de Causis in which these substances are labeled as limited

upwards and unlimited downwards (infinite inferius et finite superius).

The first conclusion that is drawn from

the way its essence is found in this substance is that God does not belong to a genus. The

second statement that is made about God is that, although he is Pure Existence (esse tantum),

he is not universal being (esse universale), which is common to all existents. We must

therefore take care not to fall into the error of panentheism, the doctrine that God is universal

being, which was declared a heresy. Thomas also refers to the Liber the causis to explain the

way in which the First Cause, which is Pure Existence, is individuated, namely the purity of

its goodness. In addition, Gods Pure Existence means that he possesses all the perfections

which are found in the diverse genera, but in an even more perfect way than that the diverse

things possess them; these perfections are included in the singular perfection of his being

which is Pure Existence.

11

How essentia is found in accidents

Since (designated)

matter is the principle of individuation, there can only be one individual in every species of

angel. The human soul is individuated by the human body with which it forms a composite

substance. Death does not negate the individuating effect of the body during its lifetime, since

the human soul has become the form of an individual (designated) body. The principle here is

that an effect may continue after its cause has ceased to exist.

Thomas asserts that the essence is what is signified by the definition, and that by extension,

the essence of accidents is similarly signified by their definitions. However, accidents include

other substances in their definition, precisely because they cannot exist on their own. For

example, in the definition ‘the mind of Plato’, Plato is the possessor of the being which is

accidental, i.e. the mind. The individuating principle in this instance is the designated matter

10 Leon. 43.5:2-3. 11 Leon. 43.5:52-53.

42

of the substance in which the accident exhibits. Accidents do not have a material component

themselves. Hence, accidents have incomplete essences. In addition, accidents share in the

existence of the subject that they are dependent on, so that just as the composition of matter

and form in the substance result in substantial existence, the conjoining of substance and

accident results in an accidental existence. The express difference is of course that the

material component in composed substances does not exist prior to its composition with

substantial form, except as purely conceptual prime matter, while the substance to which an

accident is added exhibits prior and independent existence.

The accidents can be differentiated into two kinds: the first kind derives from the form of its

subject. Some examples are the activities of the human intellect, such as thinking and feeling,

which derive from the form of the human composite, namely the human soul. These accidents

derived from form may be shared by all the members of a species, for example the capacity to

understand an intellectual argument. The second derives from matter in relation to either

specific or generic form. Examples of this kind of accidents are gender (related to specific

form) or weight (related to generic form) in humans. This kind of accidents is always

particular to an individual, in the sense that they are not shared by all members of the species

(since not all humans are male, or have the same weight). Both kinds of accidents can be

ordered into species and genera, although only considered in the abstract (in se). Only

substances can be ordered into the species and genera while considered in the concrete.

How essence is signified by terms of first and second intention

A considerable part of the De ente et essentia is dedicated to the way in which we gain

knowledge of matter-form compositions as they exist in reality, and what precisely forms the

content of such knowledge; furthermore, it is examined which logical relations exist between

these intellectual concepts. To gain a better understanding of this, it is necessary to look at

three possible relationships: (1) between the non-designated and the designated, (2) between

the unexpressed but unexcluded and the expressed but included, and (3) between that which is

signified with precision (excluding) and that which is signified without precision (non-

excluding). If we look at the example of species (man) and individual (Socrates), we know

from the exposition on materia signata that the essence of man differs from the essence of

Socrates as the non-designated (a body) from the designated (this body). However, both

essences can be said to consist of matter (body) and form (soul). Similarly, the essence of the

genus (animal) and that of the species (man) differ as the non-designated from the designated,

43

although not through matter as an individualizing principle, but through the specific

difference (rational) which is taken from the form; the specific difference is said to be

“rational” since it expresses the natural or proper activity of the human soul. The generically

expressed essence is the whole of the specifically expresses essence, in that we may say that

“man is an animal”. This direct predication would not be possible if the generically expressed

essence constituted an integral part of the specifically expressed essence. Moreover, whatever

is expressed determinately in the species, is expressed indeterminately in the genus, like when

a man is defined as a “rational animal”, since “rational” is not implied by “animal”, but also

not excluded.

Thus, the genus, the difference, the definition and the species all signify the whole of the

essence, although in different ways. The genus is taken from matter and signifies the essence

indeterminately. The difference is taken from a determinate form and signifies the essence

without determination of matter. The species and definition both express determinate matter

and determinate form. This means that in the example of man, the genus “animal” is taken

from matter (“sensitive body”) without determination of form (for example, “rational”), while

the difference is taken from the form (“rational” as the principle of the proper activity of the

human soul) without determination of matter (for example, ”body”). Therefore, what is

determinately expressed by the genus is outside the meaning of the difference and vice versa.

It should be noted that “taken from” does not imply identity: species is not identical to form,

but it is taken from form to signify the whole. The same applies to the difference. Both the

species and the definition are taken from the composite of matter and form to signify the

whole. In contrast, matter and form do not signify the whole of the composite, but

components of it. Therefore, one can say that Socrates is a man, an animal, and rational, but

one cannot say that Socrates is a body or a soul; rather, Socrates has a body and a soul.

Since in the angels and in human souls, essence is distinct from existence, they can be ordered

into the categories, according to genus, species and differentia. It is precisely because of their

composition of essence and existence that the intelligences may be said to be ordered in the

genus of substances. Moreover, we have already concluded above that every intelligence is a

species unto itself. Human souls constitute yet another species. However, their essential

differences remain hidden to us, so that we have to say that they can be ordered into genus,

species and specific difference on account of their composition of esse and essentia (an

ontological claim), not that we can so order them (which would constitute a epistemological

or logical claim). In fact, even in sensible substances the essential differences remain hidden

44

to us, but we take their accidental differences to be signs of their essential differences, and we

order them accordingly.

The separate substances also differ from the composed substances in the way in which the

genus and the difference are taken from the substantial essence. As discussed above, in

sensible substances, both the genus and the specific difference are taken from a part of the

substantial essence, which is the composite of form and matter; the difference being taken

from its form, and the difference being taken from its matter. But since the separated

substances exhibit a simple essence, one only composed of subsistent form, their genus and

difference has to be taken from the whole essence. However, the genus is taken from a

commonality in which all intelligences and human souls share (intelligence, immateriality, et

cetera), while the difference is taken from that which differentiates all the species of separate

substances from each other: their distance from the First Cause, or their specific ratio of

potentiality and actuality. From this it becomes clear that the intelligences lack definition. We

cannot give a definition based on matter and form, like we do when we say that man is body

and soul, for the separate substances lack matter. Moreover, we cannot give a definition based

on genus and specific difference since these remain unknown to us.

A rejection of Platonism

In the third chapter of the De ente et essentia (according to the Editio Leonina) Thomas

explicitly rejects the thought that words that denote genus, species or differentia signify actual

existents, such as contained in the Platonic world of Ideas. Thus, the word “man”, denoting

the species of Socrates, does not signify a Platonic Idea “Man”, which exists in the Platonic

world of Ideas, and in which Socrates participates. The reason for this is quite simple: if it

were true that “Man” constituted a separate existent, than the (true) proposition “Socrates is a

man” would imply that the existent called “Socrates” and the existent “Man”, which is

separate from Socrates, are identical; this is obviously erroneous. Furthermore, knowledge of

the existent “Man” would not be able to convey any knowledge about the existent “Socrates”

because of their separation.

Non-Platonic essences may be considered in two ways: on the one hand they may be

considered as absolute or “in the abstract”, such as when we consider a human qua human.

Considered in this way, an essence is neither plural nor singular, for neither being one, nor

being many, is included in the understanding of an essence considered in the abstract. Thus, it

does not belong to the essence of humanity to be either one (for we know that at present more

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than one human exists) or many (because Adam was alone in Paradise). On the other hand,

essences may be considered “in the concrete”, and this may be further differentiated into

essences considered in reality and essences considered in the mind. This threefold

consideration is identical to Avicenna’s differentiation into essences considered in se, in re

and in intellectu.

Thomas Aquinas on universals

The question arises whether or not the words that denote species (or genus or specific

difference), such as “man”, can be labeled as a universal. It should be noted that the

proposition “x is a man” is true for a number of individual existents; therefore it seems that

“man” is indeed a universal. But according to Thomas, in order for it to be considered a

universal it has to satisfy a few criteria: (1) it has to signify that essence as a whole, so

“humanity” is not a universal, (2) it has to be considered non-absolute, or “in the concrete”,

(3) it has to be considered according to the existence it has in the mind, and (4) it has to be

taken in relation to the individuals of which it is the common likeness. The concepts in our

minds are universal in that they may be applied to a multitude of individuals. But at the same

time, the concepts in our minds are individual because they exist in individual minds. The

universal applicability of concepts moved Averroës to assert that all humans share a singular

intellect. However, Thomas rejects this notion in favor of individual minds and concepts.

This means that within the ongoing debate between realists, who pose that universals exist in

reality, and nominalists, who state that a universal is just a name or a word, Thomas seems to

be taking position in the middle of the two factions. On the one hand, he rejects the notion of

the Platonic Ideas or the logical notions of genus, species and specific difference as truly

existing in reality. On the other hand, he posits that a universal is more than a simple name or

word. True, the universal does exist in individual minds only, but at the same time it is taken

from a constituent part of composites which actually exist in reality. It is a mental concept

which is inherently linked to extramental substances of which it expresses a common liking.

This resolution which Thomas proposes is not only elegant, it also takes away many of the

difficulties in radical realist or nominalist perspectives on ontology.

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Conclusion

As mentioned in the introduction above, the aim of this thesis was to establish an initial

understanding of the metaphysics of Saint Thomas Aquinas by looking at one of his first

literary works on the subject. Granted, the De ente et essentia does not constitute a complete

summary of all the metaphysical thought that Thomas would develop, nor does it even present

a complete ontology, as it fails to treat on the inherent nature of being, but it is an attractive

treatise to start with, because of its brevity and its concise treatment of the first principles of

being. Beyond simply looking at the content of the De ente et essentia, two additional aims

were added. First, the historical-philosophical context in which Thomas wrote his partial

summary of Aristotelian ontology was examined. A second aim was to look at the opusculum

with special attention for the philosophical influence of the Persian polymath Avicenna. The

outcome of these three tasks has been described in three separate chapters.

The historical-philosophical context was discussed in the first chapter. We saw that the

environment in which Thomas wrote the De ente et essentia was one of new developments,

while at the same time ecclesial authorities sought to lessen their impact on traditional

teachings. These new developments were due to several different factors: On the one hand,

the manuscripts of the Greek works of Plato and Aristotle were once again becoming

accessible after the sack of Constantinople (1204) during the fourth crusade. The Eastern

Schism had resulted in a dramatically decreased contact with the churches of the Greek

Patriarchates, who preserved the ancient Greek texts in the libraries of their monasteries. This

meant direct access for Christian theologians of the Latin Church to texts which they

previously only knew through citations, references and commentaries by other scholars.

Although Thomas did not read Greek, for some European theologians this new availability of

the original texts of Plato and Aristotle (and several other Neo-Platonic texts) meant that they

could for the first time examine the source of the doctrines which they were discussing.

On the other hand, the intermingling of cultures on the Iberian Peninsula facilitated the

exchange between the bearers of Jewish, Christian and Islamic cultures. Through translations

of Arabic manuscripts, Christian theologians now had access not only to the literary works of

Aristotle, but also to commentaries on these works by some of the most esteemed

philosophers and theologians of the Arabian world. Without the vast interchange of

information that happened in al-‘Andalus, Europe would not have become acquainted with the

thought of Averroës, or the poems and philosophical works of Avicenna. Thomas lived in a

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timeframe in which the translations of these works were becoming widely available, and as a

result, their contents were fiercely debated by Christian theologians. In combination with the

translations of Arabic commentaries, this lead to a great many discussions on the correct

interpretation of the original sources, and on the best possible solutions to the questions they

posed to Christian theologians. These discussions and debates were the driving force behind

the Scholastic method, giving rise to the disputatio as a didactic device.

The influence of these debates on the De ente et essentia becomes clear in various passages

where Thomas objects against the views of proponents of several distinct philosophical topics

(such as the Franciscans with regard to the doctrine of spiritual or incorporeal matter, which

had its origin in the writings of Avicebron, and the “Platonists” with regard to the real

existence of essences independent of concrete individuals). The thought of Averroës is

another influence on the opusculum, which Thomas sometimes references as an authoritative

source, while at other times he clearly objects to certain statements made by “the

Commentator” (for instance, his conclusion from the nature of universals that there exists

only one, singular intellect).The De ente et essentia thus constitutes a partial summary of

Aristotelian ontology which includes a brief discussion (and refutation) of alternative

interpretations of some central metaphysical notions. Just like the era in which the De ente et

essentia was written is characterized by discussion and dialogue, the work itself goes beyond

the mere presentation of the Thomistic interpretation of Aristotle; alternative opinions are

presented, and oftentimes criticized by Thomas.

The question arises whether within this literary discussion of Aristotelian ontology,

Avicenna’s voice could be considered as the one closest to that of Thomas. In other words:

does Thomas value the Avicennian interpretation and expansion of the Metaphysics of

Aristotle above all other interpretations? The second chapter was dedicated to looking at

Avicennian thought in the metaphysics of Thomas as it presents itself within the De ente et

essentia. I believe that, at least within the confines of the De ente et essentia, the

abovementioned conclusion is warranted. Three points support my conclusion: first, the

evaluation of explicit references made to other authors in the De ente et essentia shows that

Avicenna is referred to more than any other author. Secondly, while the mere quantity of

references in itself does not prove anything, we see in the De ente et essentia that Thomas

only refers to Avicenna in agreement with his statements, while other authors are at times

referenced to present an argument contrary to the interpretation of Aristotle presented by

Thomas. Thirdly, in addition to the quantity and content of explicit references to the works of

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Avicenna, various passages of varying length exhibit a likeness to Avicenna’s treatment of

similar topics. Some discuss the same thought in different wording, while others are either

paraphrases or verbatim citations of Avicennian texts.

Taken together, the three points mentioned above make the proposition, that the metaphysical

thought of Avicenna constitutes the single largest influence on Thomas’s interpretation of

Aristotelian ontology, at least plausible. In my opinion, this proposition is not only plausible

but also true. If we limit our evaluation of the metaphysics of Thomas Aquinas to the

exposition of Aristotelian ontology which he presents in the De ente et essentia, then we must

conclude that more than any commentary on the Metaphysics of Aristotle, the Latin

translation of the Ilāhiyyāt determined the way in which Thomas interpreted Aristotelian

ontology. In addition, Thomas refers to the Latin translations of other parts of Avicenna’s

Kitāb ash-Shifā’, for example the part on the soul (De anima) when discussing the

composition of esse and essentia in simple substances. Therefore, in the broadest sense we

could say that Avicenna constitutes the most influential author with regard to Thomas’s

interpretation of Aristotelian ontology as presented in the De ente et essentia. In a more

specific sense it could be argued that Avicenna’s Sufficientia is the lens through which

Thomas read Aristotle’s Metaphysics. The most specific identification of the single largest

influence on the De ente et essentia would be the Latin translation of the Ilāhiyyāt by

Avicenna.

The question why Thomas was so heavily influenced by Avicenna’s philosophy is not easily

answered, since any attempt to answer that question would constitute speculation on

Thomas’s thoughts and preferences. However, it seems likely that Thomas recognized in

Avicenna’s interpretation of Aristotelian metaphysics at least the possibility to incorporate

certain points regarding Creation. Or to be more specific, Avicenna’s Metaphysica constituted

a first attempt to reconcile theology of Creation with Greek ontology, from an Islamic

perspective, which Thomas adapted to his own desire to clarify the relationship between

Creation and its Creation, but from a Christian perspective. The introduction by Avicenna of

the real distinction between existence and essence provided the pivotal building block for

such a reconciliatory interpretation of Aristotelian ontology.

With regard to the content of the De ente et essentia, which was briefly and thematically

summarized in chapter 3, it can be said that some of the basic premises of Thomas’s early

thought on metaphysics originate in the Avicennian Book of Healing. What follows is a list of

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the most important notions from the De ente et essentia which can safely be attributed to

Avicenna, because Thomas explicitly refers to their origin in the Avicennian corpus. The

numbers in parentheses refer to explicit references made by Thomas as presented in Table 1.

• Being and essence is what the intellect first conceives (1).

• Form signifies the perfection of each thing (2).

• The quiddity of composed substances is the composition of form and matter (3).

• Genus is not understood in the difference as part of its essence (4).

• The quiddity of a composite is not the composite itself (5).

• Form is the principle of difference (6, 12).

• The intellect causes universality in things (7).

• The quiddity of a simple substance is the simple substance itself (8).

• There are many species of simple substances (9).

• The individuation of and multiplication of souls depends on the body in the beginning,

but not in the end (10).

• Form in things composed of matter and form is the simple difference of that which is

constituted by it (11).

• Only species composed of matter and form have a simple difference (13).

In addition to these notions, the Avicennian origin of Thomas’s interpretation of the real

distinction between esse and essentia in composed substances is asserted by several authors.

John Wippel comments in his handbook on Aquinas’s metaphysics: “Avicenna has often been

cited, both by thirteenth-century writers and by twentieth-century scholars, as an early

defender of real distinction between essence and existence in such entities”.1 Wisnovsky

examines the origin of the Avicennian interpretation of the real distinction between essence

and existence in creatures in no less than three chapters of his Avicenna’s Metaphysics in

Context.2

1 JOHN WIPPEL, The Metaphysical Thought of Thomas Aquinas: from Finite Being to Uncreated Being, Washington 2000, 134.

Even though he does not specifically refer to Thomas as a philosophical heir to the

Avicennian distinction, he does examine the roots of the Avicennian distinction in the so-

called Ammonian synthesis, a Neo-Platonic reconciliation of Platonic and Aristotelian

philosophy, which Avicenna in turn tried to synthesize with theological claims made by

Islamic dogmatic theologians. Parviz Morewedge connects the Avicennian formulation of the

distinction to later Islamic and Scholastic philosophers: “However, Ibn Sina's distinction is

2 ROBERT WISNOVSKY, Avicenna’s Metaphysics in Context, London 2003.

50

important not only because it occupies such a significant place in his own philosophical

system, but also because of the role it plays in the philosophical systems of later philosophers,

such as Ibn Rushd, Aquinas, and Ockham, who took issue with what they believed to be his

formulation of the distinction, and in so doing, centered some of their own significant

doctrines around the alleged Ibn Sinian distinction”.3

But maybe more important for a proper understanding of Thomas’s early metaphysical

thought is not the admission that it is influenced by, or indebted to, the thought of Avicenna,

but the realization of the way in which Thomas went beyond Avicenna and “superadded” his

own philosophical notions to arrive at a new way of viewing the relationship between creation

and its creator. More specifically, it is precisely in the addition of the notion of an admixture

of potency and act in created beings, that the De ente et essentia does not constitute a mere

summary of Aristotelian ontology as interpreted by Avicenna, but a philosophical work which

in and of itself is “highly original”, to once again quote Weisheipl.

In addition, Morwedge challenges the

view that Avicenna proposes that existence is a mere accidental property of an essence; a

claim whose careful examination deserves a dedicated research project in and of itself.

4

Considered within these two contexts, the historical-philosophical situation in which Thomas

wrote the De ente et essentia and the major influence exerted on him by the Book of Healing

of Avicenna, the importance of this early literary work within the corpus Thomisticum

becomes apparent: although it might have been intended as a partial summary of Aristotelian

As a result of the addition

of this new way of viewing the fundamental difference between God and the created simple

substances, Thomas also starts to move away from essentialism by shifting the ontological

priority somewhat in the direction of existence, whereas Avicenna proposed the priority of

essences over existence. Thus, it seems that Thomas, while following in the footsteps of

Avicenna for the most part, starts his professional life as a magister in sacra pagina by

making an original contribution to the field of metaphysics, thereby initiating his

emancipation from Avicennian thought. This development of his metaphysical thought would

continue throughout the rest of his life. An evaluation of his latter works would probably

result in finding a greater distance between the thought of Thomas and that of Avicenna than

that is found in the De ente et essentia. But even in this early work of Thomas, the importance

of what is added is just as great as the admission of Avicenna’s influence.

3 PARVIZ MOREWEDGE, Philosophical Analysis and Ibn Sīnā's 'Essence-Existence' Distinction, in: Journal of the American Oriental Society, Vol. 92, No. 3, 425-435, 426. 4 JAMES WEISHEIPL, Friar Thomas d’Aquino: His Life, Thought and Works, Garden City 1974, 79.

51

ontology written on behalf of his fellow students at the Chapelle Saint-Jacques in Paris, a

proof of Thomas’s grasp of Aristotelian metaphysics to support his position as a magister in

sacra pagina, or even as an exposition of his stance within various metaphysical debates

meant to reassure the leadership of the Dominican Order, it actually constitutes the

philosophical groundwork on which Thomas’s theology is built. In addition to being a

summary of Aristotelian notions interpreted in such a way that they may become the backdrop

to Christian theological doctrine, Thomas presents a new and innovative interpretation of the

distinction between creation and its creator. His notion of an admixture of potency and

actuality in simple created beings is elegant in its simplicity, making the conjecture of

incorporeal matter, as proposed by philosophers of the Franciscan school, obviously

unnecessary. Furthermore, it inherently connects God and creation through the participation in

existence: every being comes to be by receiving existence from the First Cause who is also

Pure Being. In my opinion, this makes Aquinas’s interpretation of the difference between God

and other simple substances more conducive to theological and spiritual needs than the

(unnecessarily complicating) notion of incorporeal matter. Thomas’s attention for the priority

of existence over essence guides the gaze of the faithful outward to the world in which he

lives to look for signs of divine glory, instead of inward to an introspective vision of an

otherworldly realm in which pre-existent essences reside like Platonic Ideas. As such, he has

successfully incorporated the Aristotelian attention for immanence into the philosophical

fundaments of dogmatic theology. However, this does not mean a wholesale rejection of

(Neo-)Platonic doctrine; the notion of emanation from, and return to God is reconcilable with

his admixture of potency and actuality and is thus retained (although this schema of exitus and

reditus is not part of the content of the De ente et essentia). Therefore, the characterization of

Thomas as an Aristotelian, thereby denoting a negative disposition toward Neo-Platonic

thought, seems unwarranted.

Beyond the conclusions found in relation to the specific aims of this thesis, two corollary

findings warrant treatment here: the first concerns the realization of the importance of the

question: “Which text am I examining?” In contrast to (post)modern philosophical texts, there

does not exist a first or final text for the De ente et essentia. The opusculum exists in a great

number of manuscripts, of which no two appear to be identical. This is of course due to the

manner of multiplication of manuscripts before the invention of the printing press. Not only is

the copying of manuscripts by hand inherently prone to mistakes, we also have to take into

account the well intended “correction” of texts, which may lead to corruptions. For this thesis,

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I opted to treat the text of the Editio Leonina as authoritative. This in and of itself

immediately posed two problems: first, textual differences with the text prepared by Roland-

Gosselin became instantly apparent. Second, even the text of the Leonine edition is not based

on all manuscripts; rather it divides them into several groups, of which one text is treated as

its representative. This means that if you examine a small enough fragment of the text, there

might exist alternative versions, of which you will never have any knowledge unless you set

out to examine all known manuscripts. Of course, for most researchers this is simply not

possible. Therefore, one has to work with a critical version of the text, while realizing that it is

most probably not congruent with the original manuscript.

In addition to the difficulties posed by the existence of multiple manuscripts, a second set of

difficulties arises when the importance of the question “Which text does Thomas posses?” is

realized. For take the characterization of the De ente et essentia as “a partial summary of

Aristotelian ontology”; if taken for granted, it seems to imply that Thomas had access to the

Metaphysics of Aristotle. In fact, we know that he did not have access to that philosophical

treatise, and that even if he had, he would not have been able to read it, since Thomas was not

able to read Classical Greek. Thus, we have to realize the chain of translations which is

implied in that characterization: if we look at the Avicennian text which Thomas possessed,

we must admit that it was a Latin translation of an Arabic summary of Aristotelian

metaphysics, based on a translation of the Classical Greek text into Arabic, while being

heavily influenced by the Arabic commentary on that text by al-Fārābī. This is an important

realization because it means that if we want to look at “what Avicenna actually wrote” when

examining a reference by Thomas, we have to look at the Latin edition of Avicenna’s

Metaphysics (the so-called Avicenna Latinus or Liber de prima philosophia sive scientia

divina, published by Van Riet), rather than at one of many Arabic manuscripts or at a modern

translation into English of an Arabic text (like the one prepared by Marmura, for instance).

The two questions mentioned above thus illuminated the importance of knowing what text to

cite or refer to. When working with medieval texts on philosophy and theology, one always

has to be aware of the multitude of different versions of a text which might exist.

In conclusion, the extensive examination of the De ente et essentia, with special attention

being paid to its broader historical-philosophical context and the major influence exerted upon

it by the Avicennian interpretation of Aristotelian metaphysics, has provided me with a first

grasp of Thomas’s metaphysical thought. In addition to an introduction to its technical terms

and arguments, the study of the context of De ente et essentia has given me an insight into the

53

completely different scientific worldview of that era, which was concerned with truth instead

of facts, in which proper citation of sources was at most optional, and in most cases, non-

existent, and which was characterized by discussions fueled by sources which had just

become available. In addition, it has strengthened my positive evaluation of Thomas’s manner

of argumentation and philosophical creativity, as he manages to introduce new and innovative

interpretations, even in a work as small as the De ente et essentia. But working on this thesis

has also made me realize the immense size and scope of Thomas’s collected works. It has

induced a desire to extrapolate the questions I had in the back of my mind while studying the

De ente et essentia to later works, in order to see whether how Thomas’s metaphysics

developed throughout his life. Therefore, this thesis only presents a very first inquiry into a

body of philosophical thought which merits a lifetime of research.

54

Selected bibliography

Texteditions:

S. THOMAE AQUINATIS, Opusculum De Ente et Essentia: Commentariis Caietani Illustratum,

Romae 1907.

Sancti Thomae de Aquino Opera omnia, Tomus XLIII, Roma 1976.

Translations/Commentaries:

THOMAS VON AQUIN, HORST SEIDL, Über Seiendes und Wesenheit, Hamburg 1988.

THOMAS VON AQUIN, WOLFGANG KLUXEN, Über das Seiende und das Wesen, Freiburg im

Breisgau 2007.

THOMAS VON AQUIN, RUDOLF ALLERS, Über das Sein und das Wesen, Köln/Olten 1953.

EDITH STEIN, Übersetzung: Thomas von Aquin, Über das Seiende und das Wesen: De ente et

essentia - mit den Roland-Gosselin-Exzerpten, Freiburg in Breisgau 2010.

M.-D. ROLAND-GOSSELIN, Le De ente et essentia de S. Thomas d’Aquin : texte etabli d’apres

les manuscrits parisiens, Paris 1948.

THOMAS VAN AQUINO, B. DELFGAAUW, Over het zijn en het wezen, Kampen 1986.

THOMAS AQUINAS, ARMAND MAURER, On Being and Essence, Torento 1968.

THOMAS VAN AQUINO, A.M. VAN DER MENSBRUGGHE, De Ente et Essentia divi Thomae. Over

het Wezen en de Wezenheid door S. Thomas van Aquino, Gent 1941.

THOMAS VON AQUIN, DIETER KNOCH, De Ente et Essentia: Vom Seienden und Wesen, Berlin

2008.

EMILE BRUNETAU, De Ente et Essentia: Texte latin, précédé d’un Introduction, accompagné

d’une Traduction et d’un double Commentaire historique et philosophique, Paris 1914.

CATHERINE CHAPELLE O.P., L’Être et L’Essence, Paris 1956.

55

Secondary Literature

CAJETAN, LOTTIE KENDZIERSKI, FRANCIS WADE, Commentary on Being and Essence,

Milwaukee 1964.

JOSPEPH BOBIK, Aquinas on Being and Essence: A Translation and Interpretation, Notre

Dame 1965.

JOHN GOHEEN, The Problem of Matter and Form in the De Ente et Essentia of Thomas

Aquinas, Cambridge 1940.

MARTIN GRABMANN, ‘Die Schrift “De Ente et Essentia” und die Seinsmetaphysik des heiligen

Thomas von Aquin.’, in: MARTIN GRABMANN, Mittelalterliches Geistesleben, München 1926.

JOHN WIPPEL, The Metaphysical Thought of Thomas Aquinas: from Finite Being to Uncreated

Being, Washington 2000.

L.J. ELDERS, De metafysica van St. Thomas van Aquino in historisch perspectief, Dl. I: Het

gemeenschappelijke zijnde, Brugge/Vught 1981.

L.J. ELDERS, De metafysica van St. Thomas van Aquino in historisch perspectief, Dl. II:

Filosofische godsleer, Brugge/Vught 1981.

ANTHONY KENNY, Aquinas on Being, New York 2002.

JOSEPH BOBIK, JAMES CORBETT, The Commentary of Conrad of Prussia on the De Ente et

Essentia of St. Thomas Aquinas, The Hague 1974.

SCOTT MACDONALD, ‘The Esse/Essentia Argument in Aquinas's De ente et essentia’, in:

Journal of the History of Philosophy, Volume 22, Number 2, 157-172.

JAMES WEISHEIPL, Friar Thomas d’Aquino: His Life, Thought and Works, Garden City 1974.

LOUIS DE RAEYMAEKER, Vergelijkende studie over de betekenis van het “zijn” in de

metafysiek van Avicenna en die van Thomas van Aquino, Brussel 1955.

56

Avicenna/Islamic philosophy

PARVIZ MOREWEDGE, Philosophical Analysis and Ibn Sīnā's 'Essence-Existence' Distinction,

in: Journal of the American Oriental Society, Vol. 92, No. 3, 425-435.

JEAN JOLIVET, ‘Aux origines de l’ontologie d’Ibn Sīnā’, in: J. JOLIVET, R. RASHED (EDS.),

Études sur Avicenne, Paris 1984, 19-28.

ROBERT WISNOVSKY, Avicenna’s Metaphysics in Context, London 2003.

AVICENNA, MICHAEL E. MARMURA, The Metaphysics of the Healing, Provo 2005.

MICHIEL LEEZENBERG, Islamitische filosofie: Een geschiedenis, Amsterdam 2001.

57

Table 1: Explicit references to Avicenna in the De ente et essentia.

1. P:3-5

And as Avicenna says in the beginning of his

Metaphysics, being and essence are what is first

conceived in the intellect.

Metaph. 1/6:72r b A

2. 1:34-36 It is also called form, in the sense in which the word

“form” signifies the full determination of each real

thing, as Avicenna says in the second book of his

Metaphysics.

Metaph. 3/5:80 b

Metaph. 1/6:72v a

Metaph. 2/2:76r a

3. 2:45-47 Avicena, too, says that the quiddity of composed

substances is the composition itself of form and

matter.

Metaph. 5/5:90r a F

4. 2:183-187 Avicenna says that the genus is not understood in the

difference as part of its essence, but only as

something outside its essence, as the subject is also

understood in its properties.

Metaph. 5/6:90v a BC

5. 2:267-270 Whence Avicenna says that the quiddity of a

composite is not the composite itself whose quiddity

it is, even though the quiddity too is composed.

Metaph. 5/5:90r a F

6. 3:10-11 And this is why Avicenna says that rationality is not

a difference, but the principle of a difference.

Metaph. 5/6:90r b A

7. 3:99-102 Whence the Commentator says in his considerations

on the first book of On the Soul that “it is the intellect

which causes universality in things.” Avicenna, too,

says this in his Metaphysics.

Metaph. 5/1:87v b E,

87v a C-b D

58

8. 4:77-79 Whence Avicenna says that the quiddity of a simple

thing is the simple thing itself, because there is

nothing other receiving the quiddity.

Metaph.5/5:90r a F

9. 4:87-89 [rather,] as Avicenna expressly says, there are among

them as many species as there are individuals.

Metaph. 5/2:87v a A

10. 5:68-71 And this is why Avicenna says that the individuation

and multiplication of souls depends on the body as

regards its beginning, but not as regards its

termination.

De An. 5/3:14 b

11. 5:90-93 Whence Avicenna says at the beginning of his book

On the Soul that form in things composed of matter

and form is the simple difference of that which is

constituted by it;

De An. 1/1:1r b E-1v a

12. 5:93-95 [but] not in such a way that the form is the

difference, but because the form is the principle of

the difference, as the same writer says in his

Metaphysics.

Metaph, 5/6:90r b A

13. 5:101-104 This is why Avicenna says, at the beginning of On

the Soul, that only those species have a simple

difference whose essences are composed of matter

and form.

De An. 1/1:1 b E

Fragments cited from the Editio Leonina of the De ente et essentia, book 43 (pp369-381), as

[chapter]:[line numbers]. “P” stands for prologus or proöemium (introduction). References to

Avicennian sources: Metaph(ysica) or De An(ima), [book/treatise]/[chapter]:[folio

number][v(erso)/r(ecto)] [a/b] [A-F].

59

Table 2: Implicit references to Avicenna in the De ente et essentia.

1. 1 :50-52

But it is called essence from the fact that through it and

in it a real being has existence.

Log. P/1:3v b

Metaph. 1/6:72v a C

Suffic. 1/6:17r b

2. 2:10-12 Neither can the form alone of a composed substance be

said to be its essence, although some try to assert this.

3. 2:73-75 We should notice, therefore, that the principle of

individuation is not matter taken in just any way

whatsoever, but only designated matter.

4. 2:100-101 [rather], whatever is in the species is also in the genus,

but as undetermined.

Metaph. 5/3:88r a A

5. 2:105-150 We can see how this comes about if we examine how

body taken as part of animal differs from body taken

as genus; [...] And so the form of animal is implicitly

contained in the form of body, when body is its genus.

Metaph. 5/3:88r a A

6. 2:195-222 From this it is clear why the genus, the difference, and

the species are related proportionally to the matter, to

the form, and to the composite in the real world,

although they are not identical with them. […] for we

do not say that the definition is the genus or the

difference.

Metaph. 5/5:89v D-E

7. 3:16 [...] as the Platonists held [...]

60

8. 3:26-155 Now, a nature or essence signified as a whole can be

considered in two ways. [...] and it is in this way, too,

that the notion of the genus and of the difference

belong to it.

Metaph. 5/1-2:86v a-

87v b

9. 4:11-13 The strongest demonstration of this is from the power

of understanding in them.

De an. 5/2:22v b A

De an. 5/2:23r b

10. 4:41 It is easy to see how this may be so.

11. 5:5-7 [and] this is why we find some philosophers who say

that God does not have a quiddity or essence, because

his essence is not other than his existence.

Metaph. 7/4:99r b

12. 6:59-62 For, since the parts of substance are matter and form,

certain accidents follow principally on form, certain

others follow principally on matter.

Suffic. 1/6:17r b

Log. 1:4r a b

13. 6:85-86 [and] this is why it remains in him after death.

Suffic. 1/6:17r b

14. 6.102-103 But sometimes they cause accidents which are only

aptitudes, their completion being received from an

exterior agent.

Suffic. 1/6:17r b

Fragments cited from the Editio Leonina of the De ente et essentia, book 43 (pp369-381), as

[chapter]:[line numbers]. “P” stands for prologus or proöemium (introduction). References to

Avicennian sources: Metaph(ysica), De An(ima), Suffic(ientia) or Log(ica),

[book/treatise]/[chapter]:[folio number][v(erso)/r(ecto)] [a/b] [A-F].

61

Abstract

This master thesis has as its subject the treatise De ente et essentia, written by Saint Thomas

Aquinas while studying at the University of Paris, but before he became a magister in sacra

pagina. The opusculum is examined with two questions in mind: first, what was the specific

historical-philosophical context in which it was written? Second, how exactly does the

influence of the metaphysical thought of the Persian philosopher Avicenna present itself in the

De ente et essentia?

The context in which the De ente et essentia was written is characterized by a new

appreciation for Greek philosophy, particularly Aristotelian and Neo-Platonic thought, which

was due to the fact that Latin translations of Arabic manuscripts and commentaries on Greek

philosophy were becoming widely available. This meant that Arabian philosophers, like

Avicenna, Averroës and Alpharabius, became well known among Christian theologians, as

well as the writings of Proclus and Avicebron. Thomas Aquinas reacts in his De ente et

essentia on a number of theological debates which had started as a result of this influx of

philosophical thought. The prime example being the doctrine that simple beings are composed

of form and incorporeal matter, which has its origin in Avicebron, and which was defended by

members of the Franciscan Order.

The influence of Avicenna on the De ente et essentia presents itself in the number of

references that Thomas makes to his literary works, especially to the Latin translation of the

Ilāhiyyāt, a work which summarized and expanded upon the Metaphysics of Aristotle.

Throughout the De ente et essentia we see Thomas referring to Avicennian thought and at key

points, he goes beyond the writings of Avicenna to introduce new thoughts on ontology,

especially on the real distinction between essence and existence in created substances. His

innovative use of the Aristotelian notions of act and potency to differentiate the simple

substances from God is an elegant way to circumvent the need for incorporeal matter.

Thomas’s appreciation for the Avicennian interpretation and expansion of Aristotelian

metaphysics becomes quite clear from the De ente et essentia. However, at the same time, we

see the beginnings of a further development of Avicennian thought, toward the formation of a

body of thought which is unique to Saint Thomas Aquinas and which has become the

archetype of Catholic Systematic Theology.