Kahn - III.2 -Sensation and Consciousness in Aristotle’s Psychology

Sensation and Consciousness in Aristotle's Psychologyby CHARLES H. KAHN (University of Pennsylvania)

This study is conceived äs a first step towards answering thequestion: is Aristotle a dualist in bis theory of Sensation P1 Is thereänything in his account which corresponds to the traditional Carte-sian distinction between mind and mechanism, between the mentaland the physical ? If so, how are the two terms related to one an-other ? The question is easy to formulate, but surprisingly difficultto answer, and the difficulties are due äs much to the general obscu-rity of the problem of dualism, äs they are to the specific perplex-ities of the Aristotelian view. The following pages are presented,then, äs a preliminary attempt to determine just where AristotleStands with regard to one of the most controversial issues of modernepistemology.

The need for some clarification of Aristotle's position is suggestedby a stränge disagreement among his recent interpreters. In anarticle published in 1961, one writer maintains that (in the DeAnima, at any rate) "Aristotle tries to explain perception simplyäs an event in the sense organ", that is, äs a locaHzed bodily event,with no dualistic or "psychic" complications2. On the other hand,

1 An earlier version of this paper was included among essays presented to JohnHermann Randall, Jr., on his 65th Birthday, February 14, 1964.

1 would like to express my gratitude to the American Council of Learned Soci-eties for a research grant in 1963—64, which provided me with the leisure to pre-pare this study.

2 THOMAS J. SLAKEY, "Aristotle on Sense Perception", Philosophiert Review 70(1961) pp. 470ff.

The following works will be cited below by the author's name alone or (in thecase of more than one work by the same author) with abbreviated title:

J. I. BEARE, Greek Theories of Elementary Cognition, Oxford 1908; IRVING BLOCK,"The Order of Aristotle's Psychological Writings", American Journal of Philology82 (1961) 50; MARCEL DE CORTE, "Notes ex6g£tiques sur la throne aristoteliciennedu sensus communis", New Scholasticism VI (1932) 187; R. D. HICKS, Aristotle,De Anima, Cambridge 1907; G. RODIER, Aristote, Traut de l'ame, Paris 1900,2 vols.;W. D. ROSS, editions with commentary of De Anima, Oxford 1961, and ParvaNaturalia, Oxford 1955; PAUL SIWEK, Aristotelis Parva Naturalia graece et latine,Rome 1963; FRIEDRICH SOLMSEN, "Greek Philosophy and the Discovery of theNerves", Museum Helveticum 18 (1961) 150—197; WILLY THEILER, Aristoteles, überdie Seele, Darmstadt 1959.

The following works of Aristotle are cited by their initialst De Anima (DA),Generation of Animals (GA), Nicomachean Ethics (NE), Parts of Animals (PA),Parva Naturalia (PN).

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44 Charles H. Kahn

another study published in the same year holds that Aristotle'sview of perception s an act of the soul has so reduced the body'sshare in the process that "it is doubtful whether the movementor the actualization occurring when the eye sees or the ear hearshas any physical or physiological aspect"3. The possibility of suchcontradictory interpretations arises from the fact that Aristotledoes not speak the language of traditional dualism. He does notcontrast the mental with the physical, the human consciousnesswith the body to which it is attached. When he describes vision,for example, s the reception of visible forms without their matter,he does not teil us whether he is referring to the arrival of lightrays in the eye or the conscious perception of shapes and colors inthe "mind".

It is true that Aristotle does distinguish two factors in Sensation,the body (soma) and the soul (psych ), which might at first sightbe taken for the Cartesian couple, body and mind. Thus Aristotledescribes Sensation s an activity "common to both body and soul"4,"a movement of the soul <which is produced) through the body"8,or, more precisely, a movement which passes through the body andreaches "to the soul"6. Famili r s these Statements may sound,nothing could be more misleading than to equate Aristotle's notionof the psycM with the Cartesian view of the soul or mind s a dis-tinct substance, whose essence consists in conscious "thought",and which is mysteriously adjoined to a bodily mechanism withwhich it should in principle have nothing to do. In the first placeAristotle insists upon the substantial unity of body and soul: thepsycho is by definition the form and realization of a living body(De Anima II, l—2). In the second place, the psychS which operatesin Sensation is not necessarily that of men, but of animals in general.And, in a wider sense, psyche for Aristotle is something which evenplants possess.

It is impossible, then, simply to equate Aristotle's distinctionbetween body and psyM with the terms of the modern dichotomy.Yet some relationship between the two sets of terms must be es-tablished if Aristotle's psychology is to be intelligible at all. For

8 SOLMSEN, "Nerves", p. 170. For earlier disagreements on this point, see PAULSIWEK, La psychophysique humaine d'apres Aristote, Paris 1930, pp. 96 and 104.

4 De Sensu 436a 8.6 De Somno 454a 9.' DA 408b 16—17; cf. De Sensu 436b 6 δια σώματο* yiyvrrcn TTJ ψυχή.



Sensation and Consciousness in Aristotle's Psychology 45

the distinction between the mental and the physical has been soinfluential, and remains so familiär, that even those contemporarythinkers who entirely reject the principle of Cartesian dualism areobliged to make use of this dichotomy äs a negative point of ref-erence for the definition of their own view. It is precisely the lackof any such reference in the case of AristoÜe which makes his psy-chology so difficult to Interpret. It is essentially a reference of thiskind which the present study seeks to provide.

In order to make the relationship clear, the terms of the com-parison must be limited at both ends. We cannot compare all ofAristotle's psychology with all of the modern discussions of theproblem of dualism. For the purpose in hand we may ignore theindividual variations in the tradition which Stretches from theCartesian Meditations to William James' Principles of Psychology,and regard this modern view en Uoc äs accepting the fundamentalcharacter of the distinction between mind and matter: betweenthought or consciousness, on the one hand, and the physical realityof extended bodies on the other. It is the acceptance of this dis-tinction äs fundamental which will here be described äs the tradi-tional view. And we shall also refer to it äs the "modern" view,since, however antiquated it may appear to some contemporaryeyes, it remains distinctively modern by reference to Aristotle.

Our task, then, is to relate the Aristotelian terms body and psycMto the modern distinction between body and mind or consciousness.In the interest of simplicity, we may treat the concept of body äsrelatively constant, and focus our attention on the differences be-tween the two psychological terms —.between psycM and con-sciousness. Specifically, we shall use the concept of consciousnessäs a point of reference by which to define what Aristotle cälls the"sensory soul", the part or power of the psycM which operates insense perception7. But before relating it to the modern conceptwith any hope of accuracy, we must first expound Aristotle's doc-trine from his own point of view.

Since our exposition is given in language which may suggestother, more modern theories, some discrepancies in terminology

7 In concentrating here on the analysis of the sensory psych&T. am obliged toleave aside the problem of the sense object, and hence to ignore the much-debateddefinition of Sensation äs "the reception of sensible forms without their matter".I hope to return to these problems in a later study, since they must obviously beconsidered in any comprehensive answer to the question, "is Aristotle a dualist ?"



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shoi d be borne in mind. In the first place, I shall throughout use"Sensation", "perception", and "sense perception" s equivalentrenderings of the Greek aisthesis. We are not here concerned withwhat James calls the perception of "things", something more com-plex and inteilectual than mere Sensation. This would involve Ari-stotle's doctrine of incidental Sensation or Sensation per accidens(αϊσθησι$ κατά σνμβφηκός), which is not an act of the sense fac-ulty s such and therefore lies outside the present study. On theother band, Aristotle's aisthesis is not quite the modern notion ofSensation. The problem s Aristotle poses it concerns neither theimmediate data of consciousness (e.g., what are called "sense data"or "raw feels") nor the perceptions we have of our own body, but,properly speaking, any capacity possessed by living animals forobtaining infonnation concerning the outside world — for enteringinto contact with, and hence responding to, their food, their enemies,their mates, their offspring. The more distinctively human capacityfor a subjective or reflexive awareness of such Sensation is alsocalled aisthlsis, but it constitutes a special problem, to be discussedin what follows. In general, Aristotle thinks of Sensation s externaland "intentional", s directed towards an object outside the sen-tient body itself8.

It is characteristic of Aristotle that his account of Sensationshould take its starting point not from an analysis of the humanmind but from the study of living things generally — of animals,and even of plants. Yet this biological background is also indicatedby the normal associations of the Greek term psychS, whose etymo-logical value is that of a life-breath, the vital power which one "ex-pires" at the moment of death, or in a deep £aint9. This old meaningis preserved in the derivative adjective empsychos, "ha.vinga.psych£",i.e., "living, animate"; whereas apsychos, "with no psychS", desig-

8 As a result, pleasure and pain are not recognized by Aristotle s sensationsin the strict sense. See below, p. 72 with nn. 66—67.

9 See, for example, IKad V, 696—98, where the connections between ψυχή,vitality, breathing, and wind are clearly indicated:

The ψυχή left him, and the mist mantled over his eyes,but he got his breath back again, and the blast of the north windblowing brought back to life the spirit (6υμό$) gasped out in agony.

(Lattimore's transl., sh'ghtly adapted).Although the Greek term develops many special meanings of its own, it neverentirely loses contact with the underlying sense of life-breath, which is roughly thatof Latin anima, or of the "breath of life" which the Lord breathes into Adam'snostrils.




nates what is lifeless and inert. Thus classical authors may speakof the psyche of a horse or other animal; Aristotle himself appliesthe term to plants. The philosophical associations of the term areoften materialistic rather than "spiritual": most early theoristsidentified the psyche with some power in the air, some substancebreathed in by the body, or with the vital heat of the body itself10.Plato had of course underlined the contrast between the body andthe psyche or soul, but his precedent was not immediately decisive.In ordinary parlance, the antithetical term to psyche was likely tobe not "body" but "death"11.

It is within this biological, rather than strictly psychologicalcontext that Aristotle places his own doctrine of the psyche. Thecontext is clear from the methodical arrangement of the treatises,where the De Anima Stands, within natural philosophy, s intro-duction to the short essays in psycho-biology (Parva Naturalia)and to the great systematic works in zoology: the Parts and theGeneration of Animals12. This orientation is clear from the verydefinition of the soul s the form and realization of an organic body.The same biological perspective is further indicated by the factthat the list of parts or faculties of psyche begins with the "nutritivesoul", the principle of biological life s such, said to be "the primaryand most general power of psycM" (De Anima 415 a 24), the prin-ciple without which the higher powers of sense and intellect cannotexist, although it may exist without them, s it does in plants.Even in the case of animals, which are by definition sentient and

10 See DA, BookI, passim. This old, half-physical conception of the "soul"was still famili r in Descartes' time, s it was throughout antiqnity. When, in theSecond Meditation, Descartes examines "the thoughts which previously arose ofthemselves" concerning his own identity, he Claims that he had heretofore imaginedthe soul s "something extremely rare and subtie, like a wind, a flame, or a veryfine air entering into and spreading throughout my grosser parts". It is a measureof Descartes' own influence that this semi-corporeal view of the soul has beenentirely replaced by the identification of the soul with the mind or "thinkingsubstance".

11 Thus φιλοψυχέω. "to love one's psychS", means in fact to fear death.12 The intended order is clear from the cross references in the De Anima and

in most of the other treatises. See, for instance, the passages listed in ROSS' editionof the DA, pp. 7—8. A typical example (not included in ROSS' list) is G A 779 b 22:" s was said earlier in the treatise on sensations (PN), and earlier still in the discus-sion on the soul (DA)". I assume that this order is Aristotle's own, not that ofsome ancient editor, and that its significance is primarily systematic or expository,not chronological.



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must thcrcfore possess a sensory psycho, this faculty is not con-cretely separablc from their sheer capacity to live13.

Now this conception of a nutritive soul possessed by plants, andof a sensory soul shared by the lowest forms of animal life, clearlydoes not square with the traditional dualistic antithesis betweenbody and soul. Post-Cartesian authors who use the term "soul"vvould not nonnally be prepared to assign one to trees and insects,much less to bacteria and amoebas. On the other hand, there arepassages in which Aristotle analyzes the phenomena of Sensation,of memory, and of dreams, on the basis of a kind of introspectivereflection which seems characteristically modern. We shall haveoccasion to return to his special interest in the question: "Withwhat faculty do we perceive that we are seeing and hearing?" Ingeneral it is clear that Aristotle associates Sensation with somefaculty of awareness: it differs from inanimate change in that thesentient subject "notices what is going on"14. Some passages havea truly Cartesian ring, s when Aristotle asserts that the perceptionof our own existence is necessarily implied by our perception thatwe are sensing or thinking, "for our life and being <sc. s men> isproperly to sense or to think"15.

Thus if we are to comprehend Aristotle's conception of the sen-sory soul in its f ll complexity, we must be prepared to follow itfrom its roots in the vital physiology of the organism to this flow-ering in a faculty of critical awareness, including the specificallyhuman awareness of ourselves and of our own existence s think-ing, sentient beings. We must, in short, see sense perception withinthe context of Aristotle's psychology s a whole.

Consider for a moment the place occupied by the theory of Sen-sation in Aristotle's treatise on the soul. TKe De Anima opens witha double introduction. The first (occupying the whole of Book I)contains a preliminary discussion of certain fundamental problemsin the definition of the psycM, presented in the form of a reviewof earlier theories. The second introduction (consisting of the firstthree chapters of Book II) presents Aristotle's own definition ofthe soul, together with some very severe remarks on the Hmited

13 See DA 411b 28—30 and passim; in particular 414b 28fl, the comparisonof the psychic faculties to the elementary figures in geometry: "both in figuresand in animate creatures, the prior element is always present potentially in whatfollows, s the triangle is present in the square, the nutritive faculty in the sensory".

14 Physics 245 a 1: ου λανθάνει πάσχον.15 Nicomachean Ethics 1170 a 16—b l, to be discussed below.




usefulness of a general definition. To present a definition of the soulin general, says Aristotle, without specifying it in regard to indi-vidual faculties, would be like presenting a definition of geometricfigure in general, without specifying what is a triangle, a square,and the like. Accordingly, the soul must be understood by refer-ence to its specific powers of nutrition, Sensation, desire, locomo-tion, and rational thought.

The exposition proper then consists of a discussion of these fivefaculties: the nutritive in II, 4; the sensory in II, 5—12 and III,l—2; the intellect in III, 4—8; the motive and desiderative in III,9—11. Three chapters fall outside this simplified scheine16. Omittingthem froni our reckoning, we see that there are 10 chapters of theDe Anima devoted to Sensation, whereas the other three or fourfaculties together account for only 9. In terms of fullness of treat-ment there can be no doubt: Aristotle's work on the Soul is prima-rily a treatise on Sensation17. This fact underlines the close relation-ship between this work and the zoological studies; the sense facultyis for Aristotle the essential principle of the animal s such. Andthe discussion of this faculty is by no means completed in the DeAnima. Ot the short treatises which form a sequel to this work,the first, On Sense and Sensibilia, constitutes a direct continuationof De Anima II, 5—12, on the special senses. And the next threeessays (On Memory, On Sleep, and On Dreams), although they donot treat of external sense perception, deal with the "inner sense",with phenomena assigned by Aristotle to the sense faculty in itsbroadest extension, including the faculty of imagination18. Thismeans that the 11 chapters of the De Anima which deal with senseand imagination are directly supplemented by the 15 chapters ofthese four treatises in the Parva Naturalia. And since the Supple-ment is half s long again s the original exposition, it is clear thatno analysis of the latter can be satisfactory unless it takes someaccount of the former s well.

Reserving for the moment the chronological question s to whichtreatise was composed first, I propose to regard the entire discus-

1β One chapter (III, 3) deals with the imagination, which appears here s transi-tional between sense and intellect although it belongs more properly to sense. Thelast two chapters of the work (III, 12—13) form a kind of appendix on the inter-relationship of the faculties, though again Sensation is the cbief subject discussed.

17 In terms of Bekker pages, the figures are still more striking: 10 pages forsense, 3 for intellect, 4 for the other faculties combined.

18 De Insom. 459» 15: Ιστι μεν τ6 αυτό τφ ato-θητικφ το φανταστικόν, το δ*είναι φανταο-πκω καΐ αίσβητίκω έτερον.4 Arch. Gesch. Philosophie Bd. 48



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sion of the sense faculty or aisth&ikon in the De Anima and ParvaNaturalia äs one continuous exposition, whose sequence may besummarized äs follows. After a chapter dealing with the generalcharacteristics of Sensation, äs a distinct form of passivity or qual-itative change (DA II, 5), Aristotle distinguishes the several typesof sense object — special, common, and incidental (II, 6), and pro-ceeds to treat the five special senses, in five successive chapters (II,7—11). The bulk of the entire discussion of Sensation is constitutedby these chapters on the special senses. The twelfth chapter of DeAnima II then formulates a general definition of the sense facultyand the sense organ, with direct reference to the special senses dis-cussed in the five preceding chapters. The traditional division be-tween Books II and III which intervenes at this point has oftenbeen regarded äs arbitrary, since it severs two further chapters onSensation from the preceding discussion, and groups them insteadin Book III with the other faculties, including the inteEect19. With-out wishing to defend the post-Aristotelian division into books,I would point out that this break accurately reflects an importantdifference in character between the two parts of the discussion ofsense: chapters 5—12 of Book II form a unified, largely self-con-tained exposition focussed on the account of the special senses,whereas chapters l—2 of Book III are of a much looser literarytexture, dealing with a variety of miscellaneous questions, someof which are too complex for füll treatment in the De Anima. Thesetwo final chapters on Sensation thus illustrate the same type of in-complete, partially incoherent, exposition which is found in a moreextreme form in the following chapters on nouszo. The traditionalbook division serves to underline this similarity. But whereas fornous we are unfortunately provided with no sequel, some of theproblems raised in De Anima III, l—3 are discussed further, andin detail, in the Parva Naturalia.

A recent study by Irving Block has called attention to the veryincomplete and inconclusive account of the "common sense" in theDe Anima, in contrast with the much fuller doctrine on the same

19 Most editors remark that DA III. l—2 (or even l—3) might more properlyhave been included in Book II; see KODIER, II, 341, HICKS, p. 422, THEILER, p. 130,ROSS, DA, p. 268.

20 Cf. THEILER, p. 130: "Die Kapitel l—7 (of Book III) sind die schwierigstendes Werkes, nicht alles ist bis zum letzten verständlich".




subject in the first four treatises of the Parva Naturalia21. Now thetitle "common sense" refers to that part of Aristotle's theory whichis of central importance f or our own problem of the role of the soulin Sensation, and the analysis of this theory will largely occupy ourattention throughout the remainder of this paper. Our analysis will.begin on the working hypothesis — whose justification must comelater — that Aristotle's different Statements on the subject do con-stitute a single theory, rather than discrepant phases in a varie-gated development. The developmental approach to Aristotle hasbecome so fashionable that this use of an older, pre-Jaegerian meth-odology may appear anachronistic, not to say retrograde. In itsgeneral defense I must say that the developmental hypothesis seemsto me more often to mask than to reveal the true train of Aristotle'sthought äs reflected in the text. In the specific case of the theorybefore us, I shall undertake to prove that this is so, and that theDe Anima and Parva Naturalia are in essential agreement — indoctrine, of course, if not always in phraseology.

From the fact that the doctrine of the Parva Naturalia on thesubject of the sensus communis is much fuller than that of the DeAnima, Block infers that the Parva Naturalia was composed later.Now in an externally continuous exposition concerned with a singlesubject, it is plausible — though certainly not necessary — to sup-pose that the later sections were in fact written last. This of courseteils us nothing about the date of discovery of the ideas expressedat different moments in the exposition. And in any case, much moresignificant than this (inevitably speculative) question of the orderof composition is the unmistakable fact that a problem raised andtentatively discussed in the De Anima is renewed and finally re-solved in successive treatises of the.Parva Naturalia. For this meansthat the exposition is truly progressive, and that the treatises whichoccur later in the traditional, systematic order of the De Anima—Parva Naturalia do (at least in this case) represent a definite ad-vance over the preceding discussion — precisely in the same wayäs Statements at the end of any treatise will normally represent anadvance over discussioiis which appear at the beginning. This pro-gressive character of the exposition is very clearly marked in thecase of the sensus communis, that is, in the theory of all aspects ofperception which go beyond the separate Operation of the special

21 BLOCK, pp. 62 ff. I am much indebted to Block's study, despite my disagree-ment with some of bis conclusions.4*



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scnscs. Sincc this theory holds the key to our problem of the roleplayed by consciousness in Aristotle's view, we must consider itnow in detail.

Strictly speaking, the De Animo, expounds no doctrine of a "com-mon sense", although the phrase itself does appear once or twice.As we have noted, chapters 5—12 of Book II are focussed on thefunctioning of the special senses, and so exclusively focussed onthem that some Interpreters have believed that Aristotie regardsthese senses äs autonomous, self-dependent faculties, which bythemselves "accomplish all the phenomena of elementary per-ception and self-awareness"22. This is, I think, a considerable over-statement of the case, but it does truly reflect the extent to whichAristotie here refrains from introducing any sense faculty beyondthat of the individual senses. He does of course distinguish betweenidia and koina aistMta (in De Anima II, 6), that is, between specialand common objects of sense; and much of the obscurity surround-ing the doctrine of the sensus communis derives from the fact thatthis traditional (and largely post-Aristotelian) term for the facultymakes use of the adjective which Aristotie first introduces in ref-erence not to a faculty but t o a class of objects. The systematic useof the same term "common" for both object and faculty tends in-evitably to suggest a one-to-one relationship between the two,whereas in fact nothing could be more misleading. If the commonsensibles are perceived by the common sense, that is because (äswe shall see) all sense objects without exception are perceived bythis sense, which is neither more nor less than the sense facultyconceived äs a single whole. But when the common sensibles areintroduced in De Anima II, 6, they are presented äs objects of thespecial senses. When the term "common" is used in this context,it means simply that a quality like shape or motion may be per-ceived by at least two senses, sight and touch, whereas a "specialsensible" like color is perceived by sight alone. There is no Sugges-tion, at this point in the exposition, that the several senses whichperceive shape must therefore be related to some common faculty23.

22 BLOCK, pp. 63—64. A more moderate Statement of this view is to be f oundin BEARE, pp. 326—27.

23 The confusion between common sensibilia and common sense has misledeven such good Aristotelians äs Theiler, Siwek, and ROSS, all of whom would add"time" to Aristotle's list of the common sensibles in DA II, 6, on the strength ofhis Statement in De Mem. 450a 10—12 and 451 a 17. (See ROSS, DA, p. 33; THEILER,pp. 119 and 131; SIWEK, PN, p. 153, n. 24). But what the De Memoria says in fact




Such an inference would probably be legitimate. For how couldwe recognize shape-as-seen and shape-as-touched s the same prop-erty if the sensations of sight and touch were wholly separate fromone another? But Aristotle carefully refrains from drawing anysuch conclusion in De Animall, 5—12, because he is there con-cerned with the Operation of the special senses s such, and doesnot wish to obscure their analysis by introducing complicationsfrom without. The individual objects of the special senses providethe clearest and strictest case of sense perception (418 a 24). It ischaracteristic of Aristotle's method that he accordingly treats them

s if they functioned independently of one another and of any com-mon f aculty, although the mere mention of common sensibles showsthat in fact the matter cannot be so simple.

Aristotle is prepared to return to these complications s soon shis primary analysis is complete, i.e., in the first chapter of Book III.Looking back on the account f the special senses, he now under-takes to show that his account is exhaustive, and that there is nosixth sense. It is in this context that he reverts to the problem ofthe common sensibles. There is no special sense organ for the per-ception of such qualities s motion, shape, and number, says Ari-stotle. If there were, these qualities would be special objects oftheir own sense and we would perceive them by sight and touchonly incidentally, s by sight we may recognize that something ishot or sweet. But in fact there is no such special organ or sense formotion, shape, size, and number. Although they are true sense ob-jects, perceived per se and not incidentally, they are objects of acommon sense (αίσθηση κοινή), that is of a faculty shared by morethan one special sense24.is that time is perceived by the common faculty, the πρώτον αισθητικόν. Nowif a property is to be a common sensible s defined in DA II, 6, it must first be theobject of at least two special senses. (So also DA III, l, 425b 4ff.; De Sensu 437a 8.)Time, however, is not directly perceived by any external sense, much less by morethan one. (Since time is the "number of the motion" for Aristotle, it is of coursedirectly related to the common sensible, motion. But the sense of time is not iden-tical with the sense of motion; if it were, it would be common to all animals.)

24 DA 425 a 14—29. Some Interpreters (including Beare and ROSS) have failedto see that ων εκάστη αΙσΟήσει αίσθανόμεθα κατά συμβεβηκός in line a 15 is partof the hypothesis which Aristotle is rejecting, and have erroneously concludedthat he believed the common sensibles to be perceived incidentally by the specialsenses, although that is explicitly denied at a 24—28, and had already been ex-cluded at 418a 8ff., both of which passages recognize the common sensibles s senseobjects per se (αίσθητά καθ* αυτά).

The passage is rightly construed by Theiler (p. 131), who remarks that the



54 Charles H. Kahn

With this first mention of a common sense, Aristotle begins hisinference from the fact of common sensibilia to the existence of asingle faculty; but he begins stUl with reference to the special senses,and with no assumption of a power distinct from their own. Thecommon sense described in this passage is nothing but the coinci-dence of the special senses. Similarly in what follows. "The specialsenses perceive one another's objects incidentally, not s specialbut s one sense, when their Sensation occurs together in referenceto a single object; for example, in the Sensation of bile s bitter ands yellow. For it certainly does not require some additional sense

to declare that the two <separate qualities> are one single thing"25.This unity of the special senses is not, s such, the "common sense"of the previous section, since it is here concerned with idia ratherthan koina, with the special objects of two senses rather than withthe common objects of them all. Aristotle is in fact now taking thesecond step in his ingressive exploration of the notion of a commonfaculty. Just s the special senses share the same type of object intheir perception of the koina, so they unite in the perception of asingle object which presents their idia together. In the first casethey overlap qua faculties; in the second case they coincide in asingle, momentary act. Both points provide implicit arguments forthe convergence of these faculties in a common root or agency, butAristotle does not here make the argument explicit. He has thusfar asserted the existence of no faculty beyond that of the specialsenses and their combination.

The aporias of De Anima III, 2 bring us one step closer to suchan assertion. Here for the first time we are confronted with ac-tivities of sense which are not simply identi al with the Operationby which external objects are perceived. For Aristotle now con-siders two aspects of the reflexive act by which the sense facultytakes its own operations s object. The first aspect is the awareness

thought would be clearer if Aristotle had written ούσθανοίμεθ* &ν in line 15,The er's Interpretation is that of Kodier and of all the Greek commentators (citedby KODIER, II, 353f.). The alternative, but much less natural view is to distin-guish two senses of αίσθητόν κατά σνμβεβηκός only one of which applies to thecommon sensibles (so Zeller and others, cited by KODIER, loc. dt.; also HICKS,pp. 426f., and DE CORTE, pp. 189—91, who quotes St. Thomas to this effect.)

26 425 a 30—b 3. The words ου γαρ δη ετέρα? γε το είττεΐν ότι άμφω Ι ν areambiguous; I follow Theiler (so also Kodier and Hicks). Koss and the Oxfordtranslator (J. A. Smith) understand έτερος to refer to eifher vision or taste: "theassertion of the identity of both (bitter and yellow) cannot be the act of either ofthe senses".




of perception äs such: "since we perceive that we are seeing andhearing, it must either be by sight that we perceive we are seeing,or by another sense" (425b 12). The second aspect of the reflexiveact is the differentiation of the content of perception, that is, thediscrimination of the special sense objects fröin one another.

Since each sense ... which is present in the sense organ äs senseorgan, discriminates <or judges, krineiy the differences whichbelong to its sensible object, äs vision discriminates white andblack, taste judges sweet and bitter ..., and since we also dis-criminate white from sweet, and each of the sense qualities fromone another; by what faculty do we perceive that they differt**It must be by Sensation; for these are sensible qualities— Noris it possible to judge by <two> separate faculties <sc. by tasteand sight) that sweet is different from white, but both of thesequalities must be evident to some single faculty. <For the supposi-tion that two separate faculties could discriminate thern) wouldbe äs if I were to perceive one of the qualities and you the other,and it would then be evident that they are different from oneanother! Rather, there must be one principle which says thatthey are different (426b 8—21).With these two aporias, Aristotle has entered the area of psycho-

logical inquiry in which modern introspective philosophy normallybegins, but which he has methodically avoided untü his accountof external perception was provisionally complete. It is probablyimpossible to overestimate the importance of this difference inmethodology for an understanding of the radical contrast in con-ceptual framework between the Aristotelian and the post-Cartesianviews. For the moment we simply.remark that both of the questionsraised here really do involve an introspective, anthropocentric viewof Sensation, äs distinguished from the objective, zoological ap-proach which generally prevails in his account of the special senses.This is äs true of the second aporia äs it is of the first, despite thefact that the question is formulated äs if it referred to direct andnot to reflective perception. Aristotle asks, not, "how do we dis-criminate vision from taste?" but, "how do we differentiate whitefrom sweet?'' This is, however, merely his objective mode of fram-ing the same question. For although it is essential for animals todiscriminate between different colors or between different flavors,

26 In reading this äs a question, I again follow Theiler. The traditional punc-tuation implies a weak assertion: "by some faculty we perceive that they differ".



56 Charles H. Kahn

only men — and really, only philosophers — are interested in dis-criminating colors from flavors.

There is clearly one solution to both aporias: the special sensesmust be regarded not äs ultimately independent faculties but ratheräs converging lines, joined at the center in a single, generalized fac-ulty of sense. Thus when one directs one's attention outward, theseveral senses appear entirely distinct from one another, operatingthrough different bodily channels and focussed upon entirely dif-ferent kinds of objects; yet when the gaze is turned inward, onesees that they actually converge —'· in concrete experience, äs wewould say — in the unifying and discriminating activity of a singlecenter. And it is, of course, in virtue of this union at the center —in "consciousness", let us say — that the special senses are able toshare in the "common perception" of the same common sensibles,äs well äs to perceive one another's objects incidentally in a singlesimultaneous act. It is, in short, not only the two aporias of DeAnima III, 2, but also the two Statements concerning the unity ofthe senses in the preceding chapter, which find their füll elucidationin the doctrine of a unified sense faculty, äs expounded in the ParvaNaturalia.

We can only speculate äs to Aristotle's reasons for leaving theexposition of this doctrine incomplete in the De Anima, while hewent on to discuss intellect and locomotion. Apparently he wishedto Hnk the broader treatment of sense to the discussion of the relat-ed faculties of memory and imagination which is found in the latertreatises. He may have preferred to leave the more difficult theoriesonly partially stated in the De. Anima in order to complete his surveyof the other psychic faculties discussed in that treatise. Whateverthe explanation, we may be certain that, in Aristotle's view, theaporias of De Anima III, 2 are in fact resolved by the doctrine ofthe Parva Naturalia concerning the unitary sense f aculty, and arenot resolved until this doctrine has been stated.

In regard to the first problem — the faculty by which we per-ceive that we are seeing or hearing — the inconclusive nature ofthe discussion in De Anima III, 2 has not always been noted, andAristotle has accordingly been understood to say that the facultyof sight located in the eye is immediately aware of itself, and Standsin need of no higher or more general mode of perception27. Such a

27 So BLOCK, p. 63. On this äs on many other points, the most accurate analysisis that given long ago by Kodier (II, 266): "ce n'est pas, en effet, en tant que sensspe'cial et differencio que le sens de la vue nous donne la conscience de la vision;




doctrine would imply that the perception or "awareness" that weare hearing is of an entirely different nature, and exercised by anentirely different faculty, from the perception or awareness that weare seeing. This may or may not be a possible view, but it is certainlythe very reverse of the view which Aristotle -expounds elsewhere,s we shall see. His inconclusive discussion of theproblem herecan

only be understood s a preparation for the f ll solutionto come.The connection between the second aporia in De Anima III, 2 —

with what faculty do we distinguish colors from flavors ? — andthe final solution in the Parva Naturalia is much more definitelymarked, for the solution is adumbrated here in some detail, andthe same two examples (sweet and white) reappear both when theproblem is discussed further in De Anima III, 7 and when it isfinally resolved in De Sensu 7. The original statement of the aporia,in the passage quoted above (p. 55), asserts that the objects ofdifferent senses must in fact be perceived by some single faculty,but it does not define the nature of this faculty, nor its relationshipto the special senses. Aristotle does here suggest the formula thatthe faculty is concretely "one and indivisible, but separate in itsmode of being28". But when it comes to explaining this simulta-neous unity and plurality, Aristotle leaves us with a mathematicalanalogy: it is one and indivisible like the geometric point whichseparates two line Segments, but which is taken twice, s end-pointof each line. When Aristotle returns to this problem in the frag-mentary set of notes which constitutes chapter 7 of De Anima III29,he again makes use of the language of geometry: the air affects thepupil of the eye, this affects something eise; something similaroccurs in the case of hearing; but the final term (in each sequence)is one; and "there is one mean <for all Sensation), although its modeof being is plural" (431a 17ff.). It is in the same context that Aris-

c'est en tant qu'il participe aux cara^res communs de toute sensibilito". See alsobelow, p. 69.

28 DA 427 a 2: άμα μεν κοί αριθμώ άδιαίρετον καΐ άχώριστον το κρίνον, τφ είναιδε κεχωρισμένον (similarly in 427 a 5).

29 Ι assume that the incoherence of DA III, 7 is due to the fact that Aristotlejotted down these remarks s they occurred to him, more or less in their presentform. It is also possible that they represent mere fragments of a more polishedexposition which has been lost. In that case the present arrangement would bethat of some ancient editor ( s Torstrik and others have believed). But the firstalternative seems much the more likely, since the chain of association linking oneitem to the next has precisely the implicit and elliptical character of Aristotle'sown thought ( s Kodier and Theiler appear to have seen).



58 Charles H. Kahn

totle returns to thc problem of discriminating objects of differentsenses, and öfters another geometrical analogy, this time to themean proportional (rather than to the midpoint) between two lines.Like the mean proportional, the central faculty "is related to each<extreme> äs they are related to one another" (431 a 23). Both textand Interpretation of this passage offer considerable difficulties,which need not concern us here. What is clear, in any case, is thatAristotle explicitly reverts30 to the second aporia of III, 2 andessays a new formula for the single faculty which unites the specialsenses.

Both aporias are finally resolved in two important sections ofthe Parva Naturalia.

1. In the last chapter of the De Sensu, Aristotle returns oncemore to the problem of discriminating objects of different senses,and gives his solution in these terms31:

If the soul perceives sweet and white with different parts (ofitself), either some unity is formed from these parts or there isno unity. But there must be a unity; for the part capable of Sen-sation is one There is then necessarily one (faculty) of the soulby which it perceives all things, äs has been said earlier32, but dif-ferent kinds (of objects) through different means (i.e., throughdifferent organs)— As in the case of (corporeal) things ... some-thing numerically one and the same may be both white and sweet,... so in the case of the soul one must assume that the faculty ofperception for all (objects or qualities) is numerically one and thesame, although its mode of being is different, and sometimes dif-ferent in genus or kind (between the different senses), sometimesdifferent in species or form (within a given sense). So that a man

30 "We have said earlier what is the faculty which distinguishes sweet and hot;but we must also formulate the matter äs follows" (431 a 20).

81 De Sensu 449 a 5—20. I add in parenthesis words which are ellipticallyomitted in the Greek, but implied by the context.

32 Where has this been said "earlier" ? ROSS suggests the immediately preced-ing passage in De Sensu l, but I can find nothing there to justify the reference.Beare (in his note to the Oxford translation) refers more plausibly to DA III, 2(see esp. 427 a 5); similarly SIWEK, PN 125, n. 337, and also ALEXANDER, In DeSensu (ed. THUROT, 1875), p. 344. Perhaps the most exact antecedent is DA III,7, 431 a 19 and 28—29. The backward reference here is one sign, among many,of the contmuity of exposition between DA and PN. For another mark of conti-nuity, note the recurrence of "sweet" and "white", already offered äs examplesin DA III, 2 (426b 13ff.) and III, 7 (431b 1).



1" ** · ~~" -r·

Sensation and Consciousness in Aristotie's Psychology 59

perceives (different qualities) simultaneously with one and thesame faculty, though in its definition it is not the same.2. In the treätise On Sleep and Waking, Aristotle notes äs the

essential characteristic of sleep the incapacitation of all the sensestogether. This leads him to the classical statement öf the doctrineof sensus communis.

Each sense possesses something which is special and somethingwhich is common. Special to vision, for example, is seeing, specialto the auditory sense is hearing, and similarly for each of theothers; but there is also a common power which accompanies themall, in virtue of which one perceives that he is seeing and hearing.For it is not by vision, after all, that one sees he is seeing; nor isit by taste or by sight or by both that one judges, and is capableof judging, that sweet things are different from white ones; butit is by some part which is common to all the sense organs. For thereis one faculty of sense, and one master sense organ, although thebeing of sense is different for each genus, e.g., for sound andcolor (455a 12—22).Here the twin aporias of De Anima III, 2 are jointly recalled

and resolved in the definitive assertion of the unity of the entiresense faculty, which is now for the first time Hnked to the physio-logical doctrine of the unity of the sense apparatus in the commonsensorium, the heart (or, äs we would say, the brain), "the commonsense organ for the special organs of sense, in which actual sensa-tions must present themselves"33. It is here, in fact, in the expla-nation of sleep, that Aristotie's psychology meets his physiology;and (despite his errors of fact) the theoretical joint is perfect.

Now this "common power which accompanies all the senses, invirtue of which one perceives that he is seeing and hearing", wouldnot seem to be so very different from the modern notion of con-sciousness äs defmed by Locke, "the perception of what passes ina man's own mind"84. But before following up the comparison andcontrasts with the modern view, we must first summarize the func-tions which Aristotle assigns to this central faculty of perceptionin the Parva Naturalia, and decide whether or not this theory iscompatible with the account of Sensation given in the De Anima.

To begin with some remarks on terminology. In the first place,this "common power" (koine1 dynamis) accompanying all of the

38 De luventute 467b 28; cf. 469a 12.34 Essay concerning Human Understanding, Bk. II, eh. l, sect. 19.



60 Charles H. Kahn

special senses cannot simply be identified with the „common sense"(koM aisthosis) mentioned in the De Anima s perceiving the com-mon sensibles36. For s we have seen, the latter is defined objec-tively, by reference to certain qualities it perceives, but the formeris defined subjectively, by reference to the awareness of any Sen-sation s such. This subjective power is clearly the more general,and in no way more closely connected with the perception of thecommon sensibles (such s motion and shape) than with the per-ception of colors, sounds, and flavors. What is characteristic of boththese notions of "common sense" is that they refef to a facultylocated in the central sensorium, rather than in any special senseorgan s such. There is one passage in the Parva Naturalia and onein the Parts of Animals which seem to use the term "common sense"with just this connotation: the general faculty of sensibility locatedin the heart36; and it is this usage which has prevailed in the laterdesignation of the sensus communis. The more frequent Aristotelianexpression for this idea is, however, το (πρώτον) αίσθητικόν, "the(primary) capacity of sense"37, where for brevity the adjective"primary" is often omitted. Similar in meaning is the term κυρίααίσθηση, "Sensation proper"38. Since the faculty is defined byreference to the heart, the organ itself is even more frequently des-ignated by the corresponding terms: the "primary sense organ",the "source or principle of Sensation" (αρχή της αίσθήσεω$), the"common sense organ", or the "sense organ proper"39. All of theseexpressions refer to a single doctrine, most fully formulated in thepassage quoted from the De Somno, where the heart is referred to

35 DA 425a 27, with 431b 5 where τη κοινή (αίσθήσει) is mentioned for theperception of motion.

86 De Mem. 450 a 10 (where Imagination is said to affect the κοινή αϊσθησι$)and PA 686 a 31, where the context makes clear that this faculty is located in theheart. (The reference is to animals generally, and not orily to men.) The textualPosition of the passage in the De Memoria causes some trouble. It may well rep-resent a marginal gloss which has become incorporated into the text. In that caseit would reflect the later, more generalized use of "common sense", found in theGreek commentators.

87 After εν το αίσθητικόν ττάντων of De Sensu 449 a 17, the term πρώτοναίσθητικόν is introduced in De Mem. 450 a 11, a 14 and 451 a 16; so also De Somno454a 23. Elsewhere το αίσθητικόν has the same sense (e.g., in De Insom. 459a 12e).

88 De Somno 456 a 6.89 Πρώτον αίσθητήριον De Somno 455b 10, 456a 21, etc.; κύριον αίσθητήριον

ibid. 455 a 21, a 33; cf. το κύριον των αίσθήσεων, Tfjs αΙσθήσεω$, 8 examples inBONITZ, Index Arist. 20b 18—24; κοινόν αίσθητήριον, De luv. 467b 28, 469a 12;αρχή τη? αίσθήσεως De Insom. 461 a 6, etc.




precisely s the κύριον αίσθητήριον, the master sense-organ orsensorium proper.

Although this doctrine is not explicitly formulated ntil the thirdtreatise of the Parva Naturalia, it is very definitely implied by thefirst two, since the De Sensu speaks of "the single capacity of thesoul by which it perceives all things", and the De Memoria refersto the "primary capacity of sense" which is responsible for per-ceiving time s well s the common sensibles, and which is also theseat of Imagination40. Whether or not the treatises of the ParvaNaturalia were all planned and composed at one time, they clearlyform an integrated exposition of a single doctrine, with a definiterelationship to the De Anima s far s the theory of Sensation isconcerned. For the first treatise of the group deals with the sensefaculty in precisely the same way s the De Anima. It is focussedup n what we may call the external function of sense: the Operationof the special senses in providing information concerning the out-side world. This is the properly cognitive aspect of Sensation, andif Aristotle has so largely limited himself to this aspect in the DeAnima, that is no doubt due to his desire to emphasize the parallelbetween sense and intellect. For his analysis of Sensation (and aboveall of vision, the cognitive sense par excellence) is to serve s themodel for his analysis of the intellect.

Considered in reference to this external cognitive function, thecentral faculty appears above all s the point of convergence — ofrecognition and discrimination — between the special channels ofextemal Sensation. It is this concentric System of contact with theoutside world which constitutes Sensation proper, which is common(in principle) to all animals, and which ceases to operate in sleep41.The treatise On Memory goes beyond this primary System of Sen-sation to deal with a number of secondary functions that may beloosely described s the activity of internal sense — where "inter-nal" refers simply to the fact that these activities are exercised bythe central faculty directly, without the need for simultaneous con-

4° De Sensu 449a 7—9; De Mem. 450a 9—14 (cf. 451a 16).41 Aristotle never considers "proprioception" or muscle sense, but would no

doubt have included it under touch (which also comprises what is now distinguisheds the temperature sense). As has been noted, his treatment of pleasure and pain

is ambiguous: he sometimes describes it s a Sensation, elsewhere (and more strict-ly) s an accompaniment of Sensation. One may compare the ambiguity whichKant notices in the use of the term "Sensation" (Empfindung) to refer to pleasureand pain, in the Critique of Judgment § 3. Aristotle would have been quite satisfiedwith Kaut's distinction between Sensation and "feeling".



62 Charles H. Kahn

tact with the outside world through an external organ. The threefunctions mentioned in this treatise are: 1) the sense of time, 2) thefaculty of Imagination or image-formation (phantastikon), and3) memory, vvhich presupposes the first two. To these three func-tions of the internal sense is later added another: 4) the power ofdreaming, which also belongs to "the sense faculty considered sa capacity to form images"42. These secondary faculties all dependnot upon the momentary activity of the external senses but upona certain persistence of the motion pr Stimulus received from themin the form of "decaying sense", which is precisely Aristotle's defini-tion of the Imagination43. These powers of internal sense are not sowidely distributed among the animals, and are much more char-acteristic of human beings, in whose case they merge almost imper-ceptibly into the rational faculty44. If Aristotle refrains from intro-ducing these broader functions of the sense faculty in the De Animo,(where the Imagination is not even definitely assigned to the aisth -tikon, but treated s somehow intermediate between sense and intel-lect), he had good reasons for such restraint45. The broader con-ception of the sense faculty, including memory and imagination,would have obscured the sharp features of parallelism and contrastbetween sense and intellect which are so impprtant for the argumentof that treatise. Hence it is only in the Parva Naturalia, where senseperception is considered less s a form of cognition than s a partof the total psycho-physiology of the organism, that the notion ofthe sense faculty is definitely broadened to include these activities

42 De Insom. 459 a 21.48 DA 428b lOff., closely followed by Hobbes in Leviathan, Chapter Two.44 Whether or not all animals possess imagination*is a question which Aristotle

hesitates to answer categorically (see DA 431b 22, 414b 15, 415a 10. 428a 8—11,434a l ff.). He definitely believes that they do not all have a sense of time and thepower of memory (De Mem. 450a 15—19; cf. 449b 28—30, Met. 980a 29), andsometimes speaks s if the sense of time was inseparable from the faculty of reason(Physics 223 a 25; cf. DA 433 b 7). The close Unk between intellect and imaginationis often stressed (e.g.. DA 403a 8, 427b 16, 431a 17, b2, De Mem. 449b 31ff.),and in one case he actually refers to a λογιστική φαντασία (DA 433b 29).

45 The chronologically-minded reader might infer that Aristotle had not yet"discovered" that imagination belongs to the αίσθητικόν, s he is to teil us in theDe Memoria (450 a 10—12; cf. De Insom. 459 a 15). But in fact this is an obviousconclusion from the definition of imagination in DA III, 3 κίνησης υπό -rfjs αίσ-θήσεοο$ TTJS ΚΟΓΓ* ένέργειαν γιγνομένη (429 a 1; cf. 425 b 24: Ινεισιν αίσθήσει? καΐφαντασίαι εν τοΐ$ αίσθητηρίοις). Aristotle had no new discoveries to make inthe matter. But the relationship of these persistent phantasy images to actual Sen-sation cannot be cleared up until the faculty of sense is defined in its f ll generality;and this Aristotle is not prepared to do in the De Anitna.



— ·—-*·


of decaying sense. This extension is not required by the subject ofthe De Sensu, and it makes no appearance in that work. The broaderview is naturaUy provoked by the discussion of memory, but theDe Memoria still expounds the doctrine of the internal sense withno mention of its physiological base. Only in the third treatise, OnSleep, does the reference to the bodily apparatus become indispen-sable ; and it is at this point (äs we have seen) that the doctrine ofsensus communis receives its füll and definitive Statement46.

As traditionally presented, the concept of the sensus communisis merely a truncated form of this Aristotelian doctrine of the uni-fied faculty of perception. There are few modern expositions whichdo justice to the comprehensive unity of Aristotle's notion of the"sensory soul", and which emphasize the extent to which he goesbeyond his own methodological fiction of treating the special sensesäs independent of one another. This distortion is due to the factthat most, if not all commentators have failed to see that the DeAnima and the Parva Naturalia form a continuous and progressiveexposition. Even Sir David ROSS gives a misleading account of thesensus communis, although he recognizes that sense for Aristotleis "a single faculty which for certain purposes is specified into thefive senses, but discharges certain functions in virtue of its genericnature". ROSS lists five such functions of common sensibility:

1. the perception of the commöh sensibles2. the perception of the incidental sensibles3. the perception that we perceive4. the discrimination between objects of two senses5. the common inactivity of all the senses in sleep47.

46 Assuming, äs we must, that Aristotle knew (or thought he knew) all alongthat the heart was the actual sensorium, and did not make this discovery in thecourse of composing his treatise On Sleep, why did he reserve the announcementuntil this point, when the mention of the common organ might have simplified theearlier discussions of the common faculty ? The question involves the whole problemof Aristotelian methodology and style of exposition, and we must be satisfied herewith a few suggestions: 1) the aporetic technique aims at making things difficultbefore they are simplified — at tieing the knot properly beiore it is untied, so thatthe scope and importance of the solution may be seen; 2) the aporias concerningthe self-awareness of sense are posedinpurely psychological, evenintrospectiveterms,and could not validly be resolved by physiological considerations; the latter areintroduced only when the psychological solution is essentially complete, since 3)the soul, in Aristotle's way of thinking, is a causal principle which explains theaction of the body, and not vice versa.

47 ROSS, DA, pp. 33—36, reprinted with slight changes from the same author'sAristotle, 5th ed. 1953, pp. 140ff.



64 Charles H. Kahn

Itcms 3, 4, and 6 of ROSS' list accuratdy describe the functions ofthe central faculty in regard to the primary activity of externalscnsc perception. Item l also refers to this activity, though notquite so accurately48. (Since item 2 belongs to the sense faculty onlyincidentatty, it has perhaps no proper place on the list.) On the otherhand, this summary takes no account of the secondary or internaloperations of the same faculty, all of which involve the Prolongationof direct perception in the processes of "decaying sense": the senseof time, the capacity for Imagination, for memory, and for dream-ing49.

The more recent and detailed study of the "common sense" byIrving Block rightly emphasizes the extent to which the ParoaNaturalia takes us beyond the doctrine of the De Anima. Blockesarticle has, to my mind, definitely refuted the view of Nuyens andROSS that the Parva Naturalia represents an earlier stage in thedevelopment of Aristotle's psychology. On this point, the presentstudy simply provides a confirmation of Block's results. On theother hand, I am not convinced by Block's own chronological view,which conceives the doctrines of the two works äs "divergent if notincompatible", and which imph'es that when Aristotle composedthe Parva Naturalia he had learned much physiology and psycho-logy of which he was totally ignorant when he composed the DeAnima. Most of the arguments for this intellectual advance onAristotle's part are drawn only from silence — for example, fromAristotle's failure in the De Anima to specify the role of the heartäs central sensorium50. Once one has grasped the methodical and

48 ROSS fails to point out that the common faculty does not apprehend thecommon sensibles directiy, but via the special senses (see above, n. 23). Further-more, in bis detailed account of the common sensibles he confounds them with theincidental sensibles, following an error of Beare. (See BEARE, pp. 283ff., and above,n. 24). The true distinction is accurately formulated by DK CORTE, p. 192: "c'estprecisoment parce que le sensible accidentel, en tant qu'il est accidentel, n'affecteaucunement le sens, qu'il se distingue du sensible commun". Cf. DA 418 a 23.

49 The sense of time is erroneously listed under the common sensibles (for theerror, see above, n. 23).

In fairness to ROSS, it must be noted that the faculty of imagination and memoryis elsewhere recognized by him äs one of the "outgrowths from the sensitive faculty",although these are misleadingly compared to the quite distinct faculty of movement(Aristotle*. p. 130).

50 There are four explicit references to the heart in the DA, three of whichidentify it äs the seat of emotions such äs anger and fear (403 a 31, 408b 8, 432b 31);the fourth teils us that "the region of the heart" is in need of respiration, and statesthat the voice is produced by the soul "in these parts" (420b 25—29). In view of




ingressive stfucture of Aristotle's exposition, both here and eise-where, all such arguments from silence fall to the ground51.

There is one difference between the De Anima and the ParvaNaturalia claimed by Block which, if it were actually to be foundin these works, would imply that Aristotle had indeed changed hismind on a matter of real importance. This is the contention that,in the De Anima, the external senses are regarded s "self-dependentfaculties", which exercise not only Sensation but also self-awarenessindependently "of the function of any other organ of the body"52.Now if one considers for a moment the implications of such a view,it seems scarcely credible that Aristotle can ever have held it — orif he did, we are glad to know that he quickly repented beiore com-posing the Parva Naturalia. For what are we to make of an act ofself-awareness Hmited to the eye or to the tongue ? And can Ari-

Aristotle's general silence on physiology in the De Anima, these passages are reveal-ing enough. The doctrine of the heart s seat of the emotions might perhaps betaken from Plato's Timaeus (but see De Resp. 479b 22; Problem. 869a 5); the heartin need of breath and the rational or sensitive soul operating in the ehest can hardlyreflect anything but Aristotle's own biology. As Theiler remarks (p. 77), the mentionof the heart in 420b 25—29 shows precisely that it may have a "biological future" —by which I understand a future of exposition, not of discovery. (The passage con-tains two forward references to the De Respiratione and the relevant sections ofthe PA: 420b 22 and 421 a 6. I see no reason to suppose that both of these are"later insertions".)

There are also two implicit references to Aristotle's doctrine of the sensorium(i. e., the heart) in the mention of the Ισχατον αισθητήριον at 426b 16, and τοεσχατον again at 431a 18 (see HICKS, ad loc.). What is the πρώτον αίσθητήριονelsewhere is the Ισχατον in the DA, since in that treatise Aristotle begins his analy-sis from the external object, and hence regards the external organs s the "first".

51 Block suggests that the vagueness of the De Anima on many questions shouldbe seen s a sign that Aristotle's "views are at an incomplete stage ... and shouldnot... be taken s his final doctrine" (p. 69). Granted, s long s the incompletenessis seen s a stage in the exposition, and not in the process of discovery, concerningwhich we know nothing.

After writing this, I find that exactly the same Interpretation of Aristotle'ssilence or apparent hesitation has been given by Father Owens for the Metaphysics:the aporetic technique presupposes "only that the question at issue is not yetdecided in the minds of the 'hearers'". (The Doctrine of Being in the Aristotelian'Metaphysics', Toronto 1957, pp. 301).

For a clear example of such rhetorical or methodological hesitation on thequestion at issue, consider Aristotle's refusal to decide whether the essence of man(i. e., the soul) is located in the heart or in the brain, at Met. Z. 1035b 26.

52 BLOCK, p. 64. Block has restated his developmental hypothesis in "ThreeGerman Commentators on the Individual Senses and the Common Sense in Ari-stotle's Psychology", Phronesis 9 (1964) 58.5 Arch. Gesch. Philosnphic Bd. 48



66 Charles H. Kahn

stotle really have believed that "when the proper stimulating mo-tions reach the eye and no farther, we see" ?83 We know, of course,that the visual Stimulus must in fact pass through the optic nerveand reach the brain, or no vision occurs. Was Aristotle so muchmore ignorant of human anatomy and physiology? Certainly notwhen he vvrote the Parva Naturalia, nor when he composed hisbiological works. Despite his ignorance of the nervous System ingeneral, Aristotle was quite familiär with the optic nerve äs a chan-nel between eye and brain (it had apparently been observed morethan a Century earlier, by Alcmaeon); and he is perfectly awarethat a Stimulus must pass through it towards the brain (and thenonwards to the heart, äs he believed), if vision was to occur54. "Forsome men wounded in battle on the temple in such a way that thepassages of the eye are cut off are known to have had the Sensationof darkness äs if a lamp had gone out"56. Are we to believe thatsuch incidents were reported to Aristotle only after he completedthe De Animo, ? But in fact the close connection of sight (and hear-ing) with the brain is not a new discovery on Aristotle's part, anymore than the central role which he assigns to the heart. Both arehis own adaptations of traditional views, utilized earüer in a dif-ferent form by Plato in the Timaeus66. To suppose that this adapta-tion, which is äs complete in the Parva Naturalia äs it is in thebiological works, and which obviously required years of carefulinvestigation, had not even begun when Aristotle composed the DeAnima — in other words, to suppose that the author of that trea-tise did not know äs much physiology äs he might have learnedsimply from reading the Timaeus — this is a very stränge supposi-

58 Op. dt., p. 63 (italics added). This is essentially the view which Plato dismissesäs absurd in Theaet. 184d: "it would be rather stränge if there were many (uncon-nected) senses seated within us, like so many heroes in the Trojan horse".

54 ^For Aristotle's knowledge of what "were half a Century later to be identifiedäs the optic nerves", see SOLMSEN, "Nerves", p. 173 (with note 25); for Alcmaeon,ibid., pp. 152 and 187, n. 10.

55 De Sensu 438b 12. The passage presents some difficulties but surely thesevered by a wound on the temples must be those which lead "from the eyes to theveins around the brain" (PA 656 b 17; cf. G A 744a 10), and which nearly all com-mentators have recognized äs the optic nerves. In his note on PN 438 b 13—14,ROSS seems to doubt this obvious Identification for the curious reason that "iropotmust always means passages, not nerves". Of course, but Aristotle did not knowthey were nerves; and Herophilus, the discoverer of the nervous System, still referredto these particular nerves äs (SOLMSEN, "Nerves", pp. 186f.; cf. BONITZ,Index Arist. 623a 47—b!2).

56 See SOLMSEN, "Nerves", passim.




tion indeed, and fortunately the evidence cited by Block does notoblige us to make it*7.

The one point which Block makes that deserves very carefulconsideration is the assertion that the individual sense facultiesare located in the organs of which they are the form and realization(entelecheia), for this is truly Aristotle's doctrine in the De Anima(412b 17—413a 3; 424a 24—28).' But is this view contradicted bythe role which Aristotle elsewhere assigns to the heart s the seatof the central faculty of sense ? In De Anima II, l where he de-scribes vision, s the form or realization of the eye, he continues:"One must apply what has been said of the part to the whole livingbody; for just s part is related to part <viz., partial faculty topartial organ), so is the whole sense faculty proportionately relatedto the whole sensitive body, s such", i.e., to the whole body scapable of Sensation (412 b 22—25). The individual faculty of specialsense is thus a part of the general faculty of sense, just s the indi-vidual sense organ is a part of the general sense apparatus of thewhole body. This view of the sense faculty s a unified whole, ofwhich the special senses are parts, is not limited to the sentencejust quoted; it pervades the entire De Anima, which continuouslyrefers to the sensory power of the soul s a single unit (το αίσθητικόνor ή αίσθητική ψυχή), comparable to the faculties of intellect andnutrition. The conception of the individual senses s independentfaculties would be just s alien to Aristotle s the conception ofindividual organs in abstraction from the body of which they forma part. The doctrine of a single, unified sense faculty, of which theindividual senses are so many diverse modes or aspects, — thisdoctrine which gradually emerges s the solution to the problemsposed by the analysis of the special senses — faithfully reflects thepoint of view from which Aristotle originally began his discussionof the sensory soul.

Now this view of the sense faculty of the soul s a unified wholeunmistakably implies that the individual organs also combine to

57 For example, from the alleged fact that the external organs are the only onesmentioned in the DA, Block concluded that "eyesight is a function solely of theeye and hearing of the ear". Such an inference could be valid only if the DA claimedto give a thorough account of the physiology of Sensation, whereas in fact it doesnot deal with physiology at all—not even with the physiology of the external organs.

Even the DA, however, contains at least two references to an "ultimate senseorgan" (see above, n. 50). It is difficult to see how Block's view could be reconciledwith the second of these passages (431 a 17—19), where Aristotle recognizes a singlesensory center (μεσότη$) for vision and hearing.5*



68 Charles H. Kahn

form a unit, a physiological System, which can serve äs Instrumentfor the sense faculty äs a whole. For the sensory soul is, by defini-tion, the form and realization of the sensory body; and the unityof one is unthinkable without the unity of the other. Far from con-tradicting the psychological doctrine of the De Anima t the physi-ology of the Parva Naturalia and of the biological works is requiredif the doctrine of sense perception äs a single faculty of the soul isto be understood at all. The inference from unity of faculty to unityof physiological System is explicitly made by Aristotle himself inthe Parts of Animals (667b 21—31), where the fact that "all animalspossess a sensory soul which is actually one" is cited äs a causalexplanation for the unity of the vascular System in the heart. Ifwith a touch of the magic wand we free Aristotle from his factualerrors, we see that he is formulating (in his own language of teleo-logical causation, where function explains mechanism) almostexactly the same point which a modern zoologist makes in de-scribing the nerve net of a simple coelenterate: "it enables an animalcomposed of many thousands of cells to react äs one integratedindividual"58.

Thus the physiology of the Parts of Animals and the psychologyof the De Anima are fully compatible, and they are in fact unitedin the psycho-physiology of the Parva Naturalia. I do not pretendto know which of these three treatises was completed first59, nordo I see that the matter is öf any philosophic importance. TheParva Naturalia and the biological works are clearly in agreementon all essentials. The De Anima takes up a somewhat different pointof view, since it abstracts from all considerations of physiologicaldetail. But there is really no reason to suj>pose that the physio-logical model in Aristotle's mind, which he systematically refrains

58 RALPH BUCHSBAUM, Animals Without Backbones, Pelican Ed. 1951, I, p. 95.Aristotle discusses this integrative action from the point of view of sensory recep-tion, whereas the quotation refers to motor response; but in either case the func-tional unity of the organism is essential.

59 Perhaps the most plausible guess is that of Theiler.(p. 76), who supposes thatthe treatises DA — PN — PA — G A were composed one after another in theirpresent, systematic order. This is likely enough, if by "composed" one means putinto final form; for the occasion of composition will then have been Aristotle's lastand most comprehensive series of lectures on psychology and zoology. But we cannever know how much of Aristotle's material was prepared by him in advance,whether in his mind or on paper, long before the moment of final composition. Forthis and other reasons, attempts to reconstruct a philosophic development byanalysis of the preserved texts are largely doomed to arbitrary methods and un-certain results.




from introducing into the De Animo,, is in any way differeilt fromthat which is actually expounded by him in the other works.

Now this view of the physiological apparatus of Sense is easyenough for us to understand, if whenever Aristotle says "veins" or"channels" we substitute "nerves", and wheneyer he refers to theheart we think of the brain instead. Once these substitutions havebeen made there is nothing stränge in his notion of a central organserving äs sensorium proper, the point at which all Stimuli from theexternal organs converge and in which they must appear for anygenuine Sensation to occur. The central faculty lodged in this organobviously exercises many of the functions which we now refer to"consciousness", and which modern physiology connects with thecerebral cortex.

But if Aristotle's view of the physiological apparatus is parallelto our own, his location of the faculty is somewhat different. Foralthough the central faculty, and the "Sensation proper" which itexercises, is definitely placed in the heart, that does not preventAristotle from locating the power of vision äs such in the eye. Fornot only is the eye a necessary condition of sight — since withoutit we cannot see at all — but it contributes everything which isspecifically visual in the final Sensation. The definition of the souläs the realization of the organic possibilities of the body impliesthat the psychic power of vision is the realization of the specificpossibilities offered by the eye, although the possibility of Sensationäs such is not offered by the eye alone, but only by the central organwith which it is connected60. Since the sensory soul of a normallyfunctioning animal includes not only the general power of Sensationbut also the special faculties of external sense, it must be thoughtof äs informing the entire sense apparatus, although it does so fromits source or foundation (arche) in the heart. Thus there is a derivativepsychic power resident in the eye, a power which departs when theorgan can no longer function, either because of local injury — whenthe eye "goes dead" — or because the animal itself is no longer

60 See the quotation from Kodier in n. 27 above. It is true that the passagesconnecting the sense faculty with a special organ, or with the body äs a whole, arefound above all in the DA, whereas the PN tends to speak only of the centralfaculty in the heart. This, however, does not reflect a change of opinion on Ari-stotle's part, but only a change of subject. The DA deals with the general definitionof psychic faculties and with the theory of the special senses; the PN (except forthe De Sensu) is concerned almost exclusively with the "internal sense" — withmemory, Imagination, and generalized sensory awareness.



70 Charles H. Kahn

alive. In the case of death, the sensory soul is wholly destroyed.But in the case of local injury, for example to an eye, the psychicpower remains intact in the central organ, and may continue toexercise its visual function through the other eye.

Thus the psychic faculty of vision is indeed located in the eye,insofar äs the latter is a functioning organ of a sentient animal61.But it is certainly not located in the eye in the sense that one couldsee with the eye alone, in independence from the sensory apparatusof which it is a pari. Such a view can never have been held by Ari-stotle, nor, I suspect, by anyone eise.

Having concluded this survey of Aristotle's conception of thesensory soul, we may now attempt to correlate it more closely withthe modern notion of consciousness. There is of course no directcorrespondence between the use of the term "consciousness" in themodern tradition and the use of psycM or "soul" by Aristotle. Themodern predilection for "consciousness" is perhaps due preciselyto the fact that it does not necessarily suggest anything so sub-stantial äs a soul. And although the soul is not for Aristotle, äs itis for Descartes, a separate substance in its own right, it is never-theless an active causal principle with enough Substantive char-acter to be responsible for the unity of the living compound whichit forms together with the body. On the other hand, there are pas-sages in Greek where the philosophic usage of psycM would seemto correspond more closely to that of the modern term "mind",for example, in the epistemological sections of the Theaetetus, wheremost translators, from Jowett to Cornford, do actually make useof "mind" äs the English equivalent. But in view of the importanceof the distinction between psycho and nous in Greek, this renderingof psycM by "mind" can only lead to confusion. We are thereforeobliged to remain with the old-fashioned term "soul", äs we havedone here throughout.

61 Would it be possible to give a concrete physiological sense to this notion ofa psychic power present in the eye, and capable of local damage ? Apparently not,if it is true that severing the optic nerve produces no physiological change in theeye itself. In that case the sensory "power" which is lost by the eye is simply thecapacity to transmit Impulses to the brain (for Aristotle, to the heart). The shareof the individual organ in the sensory psychS appears to be functional only, directiyrelated to the activity of the central organ rather than intrinsic to the externalorgan itself. Yet this functional relationship of the soul to its individual Organs isthought of äs so essential — the soul itself being äs it were the function of the wholebody — that Aristotle, in discussing voice, can speak of the (sensory-desiderative)soul äs present in the region of the windpipe (DA 420b 28).




On the other band, the Greek of Aristotle's day has no term whichreally corresponds to the modern usage of "consciousness", for theprocess or condition of awareness s such. Neither the word συνεί-δηση, on which Latin conscientia was modelled (and which servestoday to translate many of the derivativesoiconscientia into modernGreek), nor the parallel formation συναίσθηση was in use in thissense in Aristotle's time. A fifth-centuiy medical author describingthe loss and return of consciousness in epilepsy resorts to a numberof different terms, all of which have for Aristotle too special, andtoo specifically intellectual, a sense to convey the same idea62.Curiously enough, it is the term for sense perception — αίσθηση— which comes closest to providing a parallel to the modern notionof consciousness in Aristotle's language. Our survey of his theoryof the sense faculty has thus been, in part, an account of the Ari-stotelian concept of consciousness. But we must note some majordiscrepancies between the ancient and the modern notions.

1. In the first place, the modern usage of "consciousness" isdominated by the need for a term to specify the peculiar qualityof mental, s opposed to bodily or physical existence, in the spiritof the Cartesian distinction. Thus Descartes himself, in restatinghis view against Hobbes' objections, emphasized the difference be-tween corporeal and "cogitative" activities: the latter include"understanding, willing, imagining, feeling (or sensing, sentire), etc.,which agree in falling under the common principle of thought, per-ception, or consciousness (conscientiae)"**. For Descartes, the term"thought" served s the most general expression for the commonproperty of all mental acts s such; other authors, like Mill, pre-

82 See the treatise On the Sacred Disease, chapters 10—20 (I cite from the Loebed. of Hippocrates, vol. II, by W. H. S. JONES). The author's most common expres-sion for "consciousness" is φρόνηση φρόνημα, φρονεϊν (cf. έφρόνησαν,. ρ. 162, 54;καταφρόνηση ρ. 176, 30); Jones' rendering "intelligence" is too narrow. But theauthor also uses σύνεσι$, γνώμη, and διάγνωσι$ in closely related senses (chs.19—20). It is characteristic, on the other hand, that he can use αίσθάνεται forthe effects of a wind s feit by inanimate objects (p. 172, 24 and 29). It would seemthat the lonic writers of the fifth Century had developed no fixed psychologicalvocabulary. It is hard to estimate the role of Democritus, but on the whole it seemsthat the tenninology of Plato and Aristotle is an Attic invention — perhaps verylargely the work of Plato himself.

68 Third Objections, reply tb objection two; translation adapted from Haldaneand ROSS. Descartes actually wrote: "(actus cogitativi) qui omnes sub ratione com-muni cogitationis, sive perceptionis, sive conscientiae, conveniunt". The Frenchof Clerselier has "tous lesquels conviennent entr'eux en ce qu'ils ne peuvent estresans pens6e, ou perception/ou conscience et connoissance".



72 Charles H. Kahn

ferred "fecling". In contemporary usage, however, "consciousness"or "states of consciousness" has preva ed s the most common re-sponse to the need which William James expressed for "a term tocover Sensation and thought indifferently", to refer to "mentalstates at large, irrespective of their kind"64.

Now it is a fact that αίσθηση (with its verb αίσθάνεσθαι) canindeed cover the whole r nge of meaning of thought, feeling, andperception, including the affective feeh'ngs of pleasure, pain, desire,and the like65. Aristotle's usage tends to be more precise, but henever really breaks with this wider meaning of the .term in non-technical Greek. Thus, although (and particularly in the De Anima)he tends to restrict αίσθηση to objective perception via the ex-temal senses, and avoids using the term for "subjective" experiencesuch s pleasure and pain66, he everywhere insists upon the closeand necessary link between aisthesis on the one hand, and pleasure,pain and desire on the other67. Furthermore, by introducing theaporias on reflective awareness in De Anima III, 2 and by finallyincluding phantasy and memory within the sphere of the sense fac-ulty, Aristotle has in effect reestablished contact between his con-cept of aisthSsis and the general r nge of thought, feeling and emo-tion designated by the term in normal usage. The only absoluterestriction lies in the AristoteUan (and Platonic) antithesis betweenthe two faculties of discernment: sense and intellect68. But since,in its concrete operations, the human intellect for Aristotle requiresat every step an internal image or phantasm provided by the f ac-ulty of sense, this restriction is not s sweeping in fact s it mightappear in principle.

The use of the term αϊσθησίξ or αίσθάνεσθαι does not permitone to distinguish in Greek between the cognitive or objective aspectof Sensation, on the one hand, — receiving Information concerning

64 WILLIAM JAMES, The Principles of Psychology, Dover 1950, I, p. 185ff.85 See, e.g., PLATO, Theaetetus 156 b where aisthSsis is used to include pleasure

and pain, desire and fear. For an example of the terin in the most general sense,s equivalent to "consciousness" or "awareness", see Apotogy 40c: death may be

the total absence of aistMsis, like a sleep in which one has no dreams. In ModernGreek to lose consciousness is literally "to lose one's senses", χάνω τά$ αϊσθήσει$·

" For an exception to this restriction, see PA 666 a 12: "the motions of pleasureand pain, and in general of all aistMsis, begin and end in the heart". So DA 431 a 10refers pleasure and pain to the activity of the αίσβητική μεσάτης.

« DA 413b23, 414b4—6, 434al—3; PN 454b 29—31, etc.68 In contrast, Thucydides could use the verb αισθάνομαι for intellectual dis-

cernment: αίσθανόμενός τε τη ηλικία καΐ προσεχών την γνώμην (V. 26. 5).




the outside world — and the subjective or affective aspect of feitawareness, where Sensation inerges with other "raw feels" such spleasure, desire, impatience, and the like. In this ambiguity theGreek usage is parallel to that of our own verbs "sensing" and "per-ceiving". Language seems to be spontaneously.objective; to specifythe subjective moment the philosopher must introduce a terminol-ogy of his own69. The most natural device is to "objectify" the sub-jective aspect of awareness by casting the perception into reflexiveform. Thus Aristotle speaks of our perceiving that we are seeingand hearing, just s Locke describes consciousness in reflexive termss the perception of "what passes in a man's own mind". The impor-

tance of this reflexive stance in modern introspective philosophycan scarcely be exaggerated; and, s ROSS has noted, Aristotle'streatment of the question contains "one of the earliest discussions,in any author, of the difficulties involved in self-consciousness"70.But it is characteristic of Aristotle that he should raise the questionof se /-awareness (in the aporia, "by what faculty do we perceivethat we are having sensations?") simply in order to focus attentionupon the primary fact of awareness s such, and that this notionof direct awareness is given a firm conceptual basis by its connec-tion with the overt zoological phenomenon of sleep. It is clearly thisnotion of a "subjective", but not necessar y reflexive awarenesswhich Aristotle has in mind when he speaks of "the common poweraccompanying all the senses, in virtue of which we perceive thatwe are seeing and hearing" (De Somno 455 a 15). This common

69 Thus in post-classical ( s in Modern) Greek, the subjective element in αϊσθησίξis emphasized by the prefix συν-: συναίσθηση (cf. συνείδησίξ, c<wscientia). Itis συναίσθηση which perhaps comes dosest to meaning "consciousness" in a lateauthor like Plotinus. For the relevant ancient theories see H. SIEBECK, "Der Be-griff des Bewusstseyns in der alten Philosophie", Zeitschrift f r Philosophie undphilos. Kritik 80 (1882) 213. For the history of the tenninology see G. JUNG,"Συνείδησι$, conscientia, Bewusstsein", Archiv f r die gesamte Psychologie 89(1933) 528. Aristotle once makes use of the term συναίσθησίξ, in Eudemian Ethics1245 b 24, but certainly not in the later sense. The meaning is simply "shared per-ception, perception together with others", s the use of συζήν in the immediatecontext shows. Similarly for συναισθάνεσθαι in the same context. At NE1170 b 4and blO, however, the sense of the verb is "to perceive at the same time", and itmay be ( s Gauthier and Jolif suggest in their commentary) that this use for "si-multaneous perception" prefigures the later sense of "apperception, consciousness".

For some links between Aristotelian κοινή αίσθησι? and doctrines of conscious-ness in later antiquity, see A. C. LLOYD, "Nosce Teipsum and Conscientia", Archivf r Geschichte der Philosophie 46 (1964) 188—200.

70 ROSS, DA, p. 35.



74 Charles H. Kahn

power is for Aristotle that of "perception proper", κυρία αϊσ6ησι$(ibid. 456 a 6), the one, central activity of sense without which thespecial senses cannot do their work. The erapirical link which Ari-stotle establishes between this notion and the phenomena of Sleepand Waking provides us with a kind of operational definition forhis concept of consciousness. "Perception proper" is neither morenor less than the normal consciousness of waking life, the facultywhich is somehow incapacitated when we fall "unconscious" insleep or syncope (455b 2—8; 456b 9ff.).

2. This general faculty of awareness is definitely located in thecommon sensorium, that is (for Aristotle) in the heart or, in loweranimals, in the corresponding part71. It is interesting to speculates to how far Aristotle would envisage "consciousness" in very

simple animals, which have no distinct organ corresponding toheart or brain. If he had known of one-celled animals, for example,and had been willing to grant them a share in "perception proper"( s he would in principle have been obliged to do, since the posses-sion of a sense faculty is included in his definition of an animal), hewould presumably have situated this capacity in the only knowncontrol center for cellular activity, in the nucleus. Of course wecannot properly commit Aristotle to a judgment on factual matterswith which he was entirely unfamiliar. It is, after all, conceivable(though very unlikely) that an acquaintance with microscopic an-imals would have led him to revise his definition of animal, or tomake some exception for the more primitive varieties. But if weassume that Aristotle would have accepted the amoeba s a trueanimal according to his own definition, he would then inevitablyhave assigned to it a "sensory soul" operating from the nucleus( s from the heart — or rather brain — in higher animals), andwould have recognized in its adaptive responses to extemal Stimulithe Operation of a faculty comparable in type to human conscious-ness, though obviously very different in degree of complexity.

There is, however, one other possibility which would not carryAristotle quite so far along the road to "panpsychism". Wakingconsciousness is, for Aristotle, the opposite of sleep, and he main-tains that "any creature which is awake can go to sleep, for it isimpossible <for the power of sense) to be always actualized"72. Ifit were demonstrated that the simpler forms of animal never go to

71 De luv. 469b 6; PA 647a 31.72 De Somno 454b 8.



m m»


sleep, Aristotle must consistently conclude that they are not awake,that is, not "conscious" in the sense he has defined. Their apparentsensory activities would then fall in — or near — the same categorys the purely vegetative responses of plante to their environment.

On this view perception proper, accompanied by .consciousness,would occur only in the higher, not in the lower forms of animalKfe. This solution might claim to be Aristotelian in principle, al-though it goes against his express conviction s to the facts. ForAristotle definitely believes that all animals do go to sleep, althoughhe admits that. this has not been proved73.

3. As we have seen above, the sensory soul is thought of s in-forming the entire sense apparatus, or s Aristotle puts it, "theentire body insofar s it is sensitive"; i.e., it does not inform hairor finger nails at all, and it informs the eye differently from the skin.At the same time, this psychic faculty is clearly centered in theheart (or, we would say, in the brain); and this fact of the centeringof the soul is normally expressed by the characteristically Aristote-lian term αρχή (τη$ αϊσΦήσεως, της αίσθητικης ψυχής): it is the"source" or "principle" of Sensation which is located in the heart74.Sensation proper occurs only when the Stimulus reaches this center;and unless it does so, the eye cannot see nor the ear hear75.

In one respect, Aristotle's localization of the sensory soul is notvery different from Descartes'. Both philosophers connect the soulwith the body s a whole; and both recognize its special relationshipto a central organ. Thus Descartes remarks that the soul is joinedto the whole body in such a way that it cannot be said to be "inone bodily part to the exclusion of the others"; yet it has its prin-cipal seat in the middle of the brain, which is the only "part of thebody in which the soul exercises its functions immediately"76; This

» De Somno 454b 14—27.74 PN 456 a 5, 461 a 6, 469 a 5, etc. It is because of this that Aristotle can

sometimes speak s if the soul s a whole were located in the heart (De Motu 703 a 8,a 37), in the region of the heart and lungs (DA 420b 28), or, more vaguely, "within"the body. So De Sensu 438b 10; recent editors notwithstanding, I believe Alexanderwas correct in referring this to the soul in the heart, not in the eye, since otherwisethe f ollowing reference to a teniple wound would be irrelevant. Similarly in De Mem.450a 28—29: "memory takes place in the soul and in the part of the body whichpossesses it" (the context shows this is the heart). And does Aristotle ever speakof the soul — s opposed to the faculty of vision — s resident in the eye ? It mustalso be the location of the αρχή that he has in mind when he speaks of Sensation sreaching ίο the soul through the body (DA 408b 16; De Sensu 436b 6).

»· PN 467b 28—29; cf. 455a 33, 455b 11, 461a 30ff., 469a 12." DESCARTES, Les passions de l'ame, art. 30—32.



76 Charles H. Kahn

agreement bctween Aristotle and Descartes is largely due to theircommon desire to explain the physiological facts. But their positionsdiverge sharply when it comes to defining the soul and its mode ofinteraction with the body. For Aristotle there can be nothing mys-terious about the soul's capacity to perceive through the eyes, sincethe soul, äs a sensory faculty, is nothing more nor less than thenatural realization of this entire physiological apparatus. For Des-cartes, who has defined body and soul äs entities which should inprinciple have nothing in common, the union of a conscious per-ception with a particular extended mechanism can only be con-ceived äs a miracle of divine providence. The great difference inAristotie's view is the total lack of the Cartesian sense of a radicaland necessary incompatibility between "thought" or awareness,on the one hand, and physical extension, on the other. The soul isdefined for Aristotle not by those properties in which no body canshare, but precisely by those capacities which only a body can pro-vide77. A philosopher who believes, äs Descartes does, that the soulis of such a nature äs to have "no relationship to extension, nor tothe dimensions or other properties of the matter of which the bodyis composed"78, can scarcely feel at home with the Aristotelian viewthat the psychic faculty of sight is in the eye äs the general sensefaculty is in the body äs a sensitive whole.

It is a more delicate question whether, for Aristotle, the specificactivity of waking consciousness or "perception proper" is äs widelydistributed throughout the body äs is the sensitive soul itself. Ari-stotie's Statements on this point are not unambiguous. They leaveno doubt that the source and principle of such consciousness islocated in the central organ, but they do not exclude the possibilitythat, at the moment of actual Sensation, the feit awareness is thoughtof äs stretching inwardly, äs it were, from the heart to the part ororgan directly concerned. In fact this seems tp follow directly fromAristotie's conception of the life activities, including Sensation, ästhe "second entelechy" of the body, the final actualization of thefirst entelechy or soul (DA 412a 19—28, b 27—413 a 1). Thuswaking consciousness, äs the füll and proper activity of the sense

77 This is, strictly speaking, true only for the nutritive and sensory soul. Theintellect äs such constitutes a special case, which Aristotle recognizes äs fallingoutside the general definition of the soul äs entelecheia of the body. The intellectcan certainly not be defined by reference to a condition from which it is separablewithout loss. See DA 413a 3—7, b 24—27; cf. PA 641a 17—b 10.

78 Les passions de V&vne, art. 30.



ir ·-"·-··—·--·-


capacity, will be located in the same place s the power itself, thatis, in the whole body insof r s it is sensitive. A conscious act ofvision, for example, would thus be located simultaneously in theheart and in the eye, though it is primarily located in the heart.This view is not to be found in Aristotle in express terms, but it ispretty clearly implied by the principles he lays down79. It is, per-haps, essentially the view of common sense s instructed by a rudi-mentary knowledge of the anatomy of Sensation. In any case, in-sofar s Aristotle's view implies a primary localization of the actof awareness in the central organ, it presents a striking analogy tosome contemporary theories of the identity between states of con-sciousness and neuro-physiological activity. But whereas mostmodern theories of identity tend to reduce the psychological aspectto the physiological, Aristotle would regard the bodily processes inSensation simply s the immediate Instrument or "matter", whoseform and final completion (entelecheia) is provided by the act ofperceptive awareness.

4. The final and perhaps the most fundamental contrast betweenAristotle's view and the modern notion of consciousness is that,for Aristotle, the act of awareness or "perception proper" is neitheridentical with thinking in the strict sense, nor does it include ra-tional thought s one of its varieties. In the traditional usage, srepresented by John Stuart Mill, "feeling" and "state of conscious-ness" are equivalent expressions for "a genus, of which Sensation,Emotion, and Thought are subordinate species"80. The intellectualact for Aristotle, however, is the work of a distinct faculty of thesoul, and the most distinct of all, since it is the only faculty whichmay ultimately be separated from the body. In its concrete opera-

79 Thus DA 426 a 9—11 says simply that "actual Sensation" is located "in thatwhich is capable of Sensation" (εν τφ αίσθητικφ). But the sense capacity itselfis located in the body qua sensitive. The localization must be thought of s func-tional: it does not of course imply that either the sensory psychS or perceptionitself is a physical entity or structure with a concrete position in the body. See n.61 above.

Professor Randall suggests to me another solution: the sense activities shouldbe located not in the organs but "in the sensible world, i. e., in the whole Situation".This view is attractive in itself, but seems to conflict with Aristotle's generaldoctrine that processes of activity-passivity are localized in the patient, in this casein the sentient animal. (See Hicks' commentary on DA 426a 2.)

80 J. S. MILL, A System of Logic, Bk. I, eh. iii, § 3. Compare Descartes' parallelgrouping of "understanding, willing, imagining feeling, etc." under the head of"thought" (above, p. 71).



78 Charles H. Kahn

tion within the human organism, this faculty is of course marriedto the rest of the soul by its intimate dependence upon the Imagesprovided by the faculty of sense and Imagination: "the rationalfaculty thinks the forms in the images" (De Anima 431b 2). Butif the gaze of the intellect is directed towards the images of senseand Imagination, can the sense faculty in turn observe the discur-sive act of reasoning ? More precisely, is the reflexive act by whichwe are aware of our own thinking an act of rational thought or anact of sense ?

There is, s far s I can see, only one passage in Aristotle whichbears directly on this point, and it seems to decide the matter infavor of sense.

The man who is seeing perceives that he is seeing and the onewho is hearing (perceives) that he is hearing, and the one whowalks (perceives) that he walks, and similarly for other activitiesthere is something which perceives that we are acting, so that if weare perceiving (it perceives) that we are perceiving, and if we arethinking (it perceives) that we are thinking. But (to perceive) thatwe are perceiving or thinking is (to perceive) that we exist — forour life and being ( s men) has been defined s perceiving orthinking; and to perceive that one is aliye is a thing which is in-trinsically pleasant81.

This passage in the Nicomachean Ethics would be decisive, exceptfor the fact that the second of the two Statements italicized abovereflects not the traditional text of Aristotle but an emendation prp-posed by Bywater in 1890. The older text is more ambiguous, andseems to hesitate between the first assertion, that there is a facultywhich perceives all our actionst including our life and existence sthinking, sentient beings (and this can only be the central facultyof sense, the "common power" defined in the De Somno), and asecond statement that "we perceive that we perceive, and thinkthat we think"82.

81 N E 1170 a 29—b 1. The words in parenthesis are elliptically omitted in theGreek.

82 NE 1170a 31—32, BEKKER: ώστε αίσθαυοίμεβ' &ν ότι αίσθανόμεθα καΐνοοΐμεν ότι νοούμε ν; BYWATER: ώστε &ν αίσοανώμεθ', ότι αίσβανόμεθα, κ&ν νοώ-μεν, ότι νοούμεν. Ι believe Bywater's emendation to be certainly correct. It notonly improves the logic of the passage but renders the expression more trench-ant and more characteristically Aristotelian; the same clause in Bekker's text isalmost absurdly redundant. The emendation was accepted by Stewart, by ROSS,



-"~"^


Now there is a passage in the Metaphysics which seems also toassert that "loiowledge and perception and opinion and thought(dianoia)" are all primarily directed to something eise s their ob-ject, but may refer secondarily to themselves83. From this it hasbeen inferred that "Aristotle does not assign all seif-consciousnessto a single central faculty. Knowledge, perception, opinion, andreason, while primarily engaged with objects other than them-selves, are described s each en passant apprehending itself '84. Butthis Interpretation transforms into a fixed doctrine concerninghuman faculties what appears in its context only s a dialectical,aporetic discussion of the problem of self-inteUection in the caseof the divine mind. The only conclusion concerning the human soulwhich seems to be justified by the passage from the Metaphysicsis that a man does not exercise self-cognizance in the same fashions deity. It is obviously true that we can have knowledge about

knowledge, and thought about thinking85; but this has nothing todo with the immediate act of self-awareness discussed in the pas-sage quoted previously from the Nicomachean Ethics. Wheneversuch direct seif-consciousness is described in the case of a humanbeing, it seems to be.assigned to the faculty which characterizes

and by most modern editors and translators. As Gauthier and Jolif remark "partoutdans le contexte l'activito de conscience est dosignoe par le mot sentir, et le lienavec la ligne suivante suppose qu'il en va de meme ici" (l'Ethique Nichomaque, II,758). Bywater himself noted that, "in default of a better word ... throughout thissection the word αισθάνεσθαι has, in addition to its ordinary meaning, a moregeneral sense corresponding to onr modern term 'consciousness'"; Contributionsto the Textual Criticism of Aristotle's Nicomachean Ethics, Oxford 1892, p. 65.

The text of Bekker has, however, made an unexpected reappearance in theGennan translation of Franz Dirlmeier (I960), who declares Bywater's emendationunnecessary without any discussion of the'problems involved. (His reference toJoachim proves nothing to the point, since Joachim apparently accepted Bywater'stext.)

83 Met. 1074b 35 φαίνεται δ* αεί δλλου ή επιστήμη καΐ ή αϊσθησι$ καΐ ή δόξακαι ή διάνοια, αύτή$ δ' εν παρέργφ.

84 ROSS, DA, ρ. 35 (= Aristotle*, p. 141). ROSS seems to be following Beare,p. 290. But whereas Beare accepted the old text of NE 1170 a 32 ("we think we arethinking"), ROSS renders Bywater's text in his own translation of the Ethics ("weperceive we are thinking"). His notion of the seif-consciousness of reason is thusapparently based only on Met. 1074b 35. Note that in this passage Aristotle doesnot use the proper term for the rational faculty (vous) but the vaguer expressionfor "thinking", διάνοια (see text in preceding note).

85 ROSS' example (in his commentary to Metaphysics 1074b 36) is apt: "themedical man knows primarily about health, and secondly that his knowledge isknowledge about health".



80 Charles H. Kahn

man s an animal, i.e., s a sentient being86. Only in the case ofdeity does Aristotle speak of νόησι$ νοήσεω$, an immediate reflexgrasping of the intellect by itself. This is an uninterrupted exerciseof pure activity. But the intermittent act of human self-awareness,regularly interrupted by sleep, appears to be the function of thesense faculty — s it is the same faculty which is responsible forthe secondary activity of the "subconscious" in dreaming.

If this Interpretation is sound, there is for Aristotle an importantdistinction, which the traditional concept of consciousness tendsto ignore, between the inteUectual activity s such, and our personalawareness of it87. In Aristotle's view, our personal consciousnesss men belongs essentially to our sentient, animal nature; so that

whereas Sensation and the awareness of Sensation are simultaneous(and really identical) acts of the same faculty, reasoning and theawareness of reasoning belong properly to different faculties, andthe two acts coincide only insofar s the faculties of sense and in-tellect are concretely united in the psyche of a particular man. Thispoint is of relatively little importance for the theory of Sensation,but of very great importance for the doctrine of the "separate in-tellect".

PostScriptProfessor Roy Finch has called my attention to the fact that the

distinction made above between the sensory self-awareness of mans an animal and the noetic self-awareness of the divine mind might

suggest a parallel with Husserl's distinction between natural andtranscendental reflection88. Although the phenomenological theoryof consciousness falls outside the limits of the "traditional" view

86 Besides the passage from the NE, see De Sensu 448 a 26—30: when one isperceiving himself or anything eise, it is impossible for him to be unaware of bisown existence at the same time. (The whole context shows that such self-awarenessis thought of s the work of the sense faculty; and this point is made explicit inAlexander's commentary ad loc,, ed. THUROT, pp. 309 ff.)

Compare Aristotle's remarks concerning the memory of intellectual objects (τανοητά): it belongs per se to the primary sense faculty, and only incidentally to theintellect (De Mem. 450a 13—14). The knowledge or apprehension of such objectsbelongs properly to nous; but the memory of this knowledge s realized in an earlier,momentary act, like the concomitant awareness of the act and like the mentalimage which provided its occasion — all this is a fr,nction of the sense faculty ofthe individual, mortal soul.

87 This distinction is made explicitly by Plotinus, and plays an important rolein bis psychology. See Enneads 1,1.11; I. 4.10.

88 See, e.g., CartesianischeMeditationen, Husserlianal, The Hague 1950, pp. 72ff.




assumed here for purposes of reference, on this point the contrastbetween Husserl and Aristotle is so instructive that it may be worthdwelling for a moment on the apparent parallel. In the first place,Aristotle would probably have recognized in the transcendentalego of the phenomenological reduction (äs •in-all modern theoriesof consciousness) an illegitimate fusion of what are for him twodistinct powers of awareness: the sense faculty we share with ani-mals and the intellectual apprehension we share with God or gods.If, for the sake of the comparison, we accept this distinction andunderstand Husserl's transcendental reflection to be an act of theintellect alone, the question remains whether Aristotle would havegranted to human beings a share in what is the characteristic actof deity, the self-apprehension of noSsis. There is perhaps no ex-plicit statement to this effect in the texts, but it might be arguedthat so much is implied by Aristotle's Suggestion that äs we are inour best moments, so is deity always89. Let us assume then thatthere is some self-awareness which belongs to the purely intellec-tual principle of the human intellect (i.e., to the active intellect),and which may be compared to the realm of transcendental self-experience in Husserl. On this assumption, the phenomenologicalreduction might be described from Aristotle's point of view äs amethodical technique for "separating" the separate intellect andestablishing it in a condition of pure self-knowledge comparableto that of the divine mind. But whereas for Husserl the transcen-dental experience of the ego so purified preserves all normal humanexperience (including memory and sense-perception) äs part of itsobjective content, the corresponding "reduction" of the Aristotelianintellect would be best represented by the actual Separation at death,and would entail a complete break with all human experience, in-cluding all memory thereof (DA 430 a 22—25). Since the Aristote-lian faculties are defined by reference to their objects, it is only thesensory faculty of the soul which can perceive sense objects and canpreserve the memory of such perception. But it is precisely fromthis perishable faculty that the intellect may be separated.

This result may serve äs a kind of reductio ad absurdum of ouroriginal comparison, and an indirect proof of incommensurabilitybetween the Aristotelian view and most, if not all, modern theoriesof consciousness. It is Aristotle's fundamental distinction betweennoetic and sensory awareness which here makes all the difference.

69 See Met. 7, 1072b25, 1075a7—10; NE 1177b26ff.; DA 430a2 withHicks' note.6 Arch. Gesch. Philosophie Bd. 48



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Kahn - III.2 -Sensation and Consciousness in Aristotle’s Psychology