What Can We Know and How Can We Know It?

Notes to Introduce Philosophical Discussion

The Fields of PhilosophyMetaphysics – the study of the nature of reality.Epistemology – the study of the nature of

knowledgeAxiology – the study of the nature of value.

Ethics –values in the realm of moralityAesthetics– values in the realm of beauty and art

Logic – principles of right reasoning

LogicThe Three Laws of Thought

The Law of Non-contradiction

The Law of Excluded Middle

The Law of Identity

Logic

The difference between deductive and inductive logicInductive Logic

The premises suggest the conclusion.Deductive Logic

The premises guarantee the conclusion.

Logic -- Deductive Reasoning

The Categorical SyllogismPremise 1: All A is inside BPremise 2: All B is inside CConclusion: All A is inside C A

BC

Epistemological QuestionsWhat is the proper definition of truth?

Options:CorrespondenceCoherencePragmatism

Is truth absolute or is it relative?Are there some things that are true objectively?

What can we know? Can we know the answers to life’s greatest questions?

Epistemological QuestionsWhat are legitimate sources of truth?

Options:ExperienceReasonRevelation (authority)

General Revelation Special Revelation

Should the Bible be considered a legitimate source of truth?

Is science the new ultimate standard for truth? Has the “scientific method” usurped philosophical inquiry

and biblical authority?

RationalismThe Rationalism of Plato

Knowledge is possible because it is innate.Fundamental ideas or principles are built right into the mind

itself and require only to be developed and brought to maturity.

We have acquired these innate ideas in our pre-existent state.Prior to its embodiment in this world, the soul was in the

presence of the forms, where it acquired knowledge of the realities.

The trauma of being born causes us to forget this knowledge, but we recall it as we begin to have imperfect contact with the sensible world. Our senses provide an initial stimulus to the recollection of our innate ideas.

Rationalism of Plato

The Rationalism of Descartes

How Descartes found Certain KnowledgeHe doubted everything doubtable. in order to find one thing that was undoubtable.He would build his knowledge upon this one undoubtable

thing.The one undoubtable thing: He was a thinking substance.

“I doubt; therefore I think.”“I think; therefore I am.”

Empiricism

What is Empiricism?Empiricism—the view that all knowledge is derived from

sense experience.

John Locke’s Empiricism

The mind is a tabula rasa (“blank tablet”) before the input of experience.

Locke’s epistemological dualism: The two factors involved in knowledge are (1) mind which knows, and (2) its ideas which are known.The ego-centric predicament: If we know only our

ideas directly, how can we be certain of their correspondence with things in the external world?

Radical Empiricism -- Hume

David Hume: The source of all knowledge is perceptions.

All ideas are derived from impressions – vivid or lively sensations.

Though we have a natural belief in self and causality (every event must have a cause), experience gives us no rational knowledge of either of these; therefore we must be skeptical of their reality.

Hume’s position is known as phenomenalism: All we can actually know is the phenomena or appearances presented in our perceptions.

Skepticism

Varieties of SkepticismCommon-sense skepticism: healthy incredulity about

unlikely or preposterous claims.Philosophical skepticism: doubt about cherished

philosophical ideas.Absolute skepticism: the denial of knowledge itself.