L ECTURE 15: C ERTAINTY

T ODAY ’ S L ECTURE In Today’s Lecture we will: 1.Review Hume’s radical empiricism and its consequences 2.Outline and investigate Kant’s theory of knowledge: Transcendental Idealism 3.Discuss whether Kant’s theory overcomes Hume’s radical empiricism 4.Conclude our investigation into the theory of knowledge

R ECAP : D AVID H UME

D AVID H UME David Hume’s Phenomenalism All knowledge is derived from and limited to appearances Appearances are presented to us in our perceptions Perceptions can be divided between 1.Impressions Lively, Vivid Sensations 2.Ideas Pale impressions / copies All ideas are derived from impressions All the mind possesses is a collection of perceptions

D AVID H UME David Hume’s Phenomenalism There are two types of knowledge: 1.Relations of Ideas Ideas that are intuitively or demonstratively certain E.g. Geometry, Arithmatic, Logic, Algebra etc. 2.Matters of Fact Ideas that pertain to the world E.g. The sun will rise tomorrow, This chair is red, etc.

D AVID H UME David Hume’s attack against abstract knowledge Empirical (all) knowledge can only be either: Necessarily true but not informative Or Informative but not certain All ideas are derived from appearances Any idea we have that is NOT derived from appearances should be abandoned When we run over libraries, persuaded of these principles, what havoc must we make? If we take in our hand any volume, of divinity or school metaphysics, for instance; let us ask, “Does it contain any experimental reasoning concerning matter of fact and existence?” No. Commit it then to the flames: for it can contain nothing but sophistry and illusion. (David Hume, Textbook, p.225) When we run over libraries, persuaded of these principles, what havoc must we make? If we take in our hand any volume, of divinity or school metaphysics, for instance; let us ask, “Does it contain any experimental reasoning concerning matter of fact and existence?” No. Commit it then to the flames: for it can contain nothing but sophistry and illusion. (David Hume, Textbook, p.225)

D AVID H UME According to Hume we must abandon the following abstract concepts: o The concept of causation We never perceive a necessary cause; only succession and contiguity o The self When we reflect we never find a thinking thing; only many different perceptions o The concept of substance We never perceive substance Furthermore: All scientific knowledge is informative but not certain We must recognize how limited our perceptions are and limit our knowledge accordingly

K ANT

I MMANUEL K ANT Outline: Lived Represents an important turning point in epistemology Wrote the Critique of Pure Reason in response to Hume’s radical empiricism

I MMANUEL K ANT Prelude to Kant’s theory of knowledge: Kant was heavily influenced by Hume’s radical empiricism “I openly confess my recollection of David Hume was the very thing which many years ago first interrupted my dogmatic slumber and gave my investigations in the field of speculative philosophy a quite new direction” (Textbook, p.232)

I MMANUEL K ANT Kant maintains the following: Kant rejects the empiricist claim that the mind is a ‘blank-slate’ He also rejects the rationalist claim that we possess innate ideas Unlike Hume Kant claims we can be certain that: Every event must have a cause Substance exists The self exists

K ANT ’ S T HEORY OF K NOWLEDGE

A Priori Independent of senses UniversalCertain A Posteriori Derived from sense experience Specific Not certain K ANT ’ S T HEORY OF K NOWLEDGE A Priori Independent of senses A Posteriori Derived from sense experience Analytic True by definition No relevance to reality Synthetic Not logically certain Kant’s understanding of ‘knowledge’

K ANT ’ S T HEORY OF K NOWLEDGE Activity: List any knowledge that corresponds to the following categories: Synthetic a posteriori Knowledge The room is red The moon is 2159 miles in diameter Analytic a priori knowledge All bachelors are unmarried men A triangle is a three sided closed shape Analytic a posteriori Knowledge Informative but not certain Certain but not informative Analytic a posteriori knowledge is not possible!

K ANT ’ S THEORY OF K NOWLEDGE The search for synthetic a priori knowledge Kant wants knowledge which is certain, not derived from experience, and still informative It must be both Synthetic and a priori Informative, not just true by definition Necessary & Universal For Example: Every event has a cause Substance exists The Self exists For Example: Every event has a cause Substance exists The Self exists The big question is whether such knowledge exists!

K ANT ’ S T HEORY OF K NOWLEDGE Traditional theories of knowledge Traditional theories of knowledge are concerned with asking whether our idea of the apple corresponds to the apple itself

K ANT ’ S T HEORY OF K NOWLEDGE Kant’s Copernican Revolution Instead of asking how our knowledge conforms to objects in the world; Kant asks how objects in the world must conform to us Instead of asking how our knowledge conforms to objects in the world; Kant asks how objects in the world must conform to us

K ANT ’ S T HEORY OF K NOWLEDGE Kant’s theory of knowledge Synthetic a priori (SAP) knowledge is not derived from experience SAP is the basis for experience SAP defines how we experience Our minds possess innate structures called ‘categories of the understanding’ UnityPluralityTotality Relations of substance and characteristics of substance Relations of cause and effect Relations of reciprocity

K ANT ’ S T HEORY OF K NOWLEDGE Space and Time Space and Time are both a priori conditions for all experience ALL objects must be in space and time to be experienced Kant maintains that space and time are contributed by our minds We can have no knowledge of an object which is not in space or time

K ANT ’ S THEORY OF K NOWLEDGE Kant’s disagreement with Hume: Hume maintained that belief in the following is irrational: Causality The self Substance For Kant these concepts are not only certainly true; They must be true! They are universal and necessary for experience If they were not true then we would not be able to have experience

K ANT ’ S THEORY OF K NOWLEDGE Summary: Unlike Hume Kant maintains that we can have knowledge which is both informative and certain: Synthetic a priori knowledge Such knowledge is universal and necessary Without it experience would not be possible Kant’s Copernican revolution makes humans, not the world, the central focus of epistemology Our minds create the conditions necessary to experience the world Space and Time Categories of the Understanding

C ONCLUSION TO T OPIC

T OPIC C ONCLUSION Rationalists Plato Descartes Chomsky Empiricists Aristotle Aquinas Locke Hume Kant’s Transcendental Idealism