Lecture 15: Certainty

Lecture 15: Certainty

In Today’s Lecture we will: Review Hume’s radical empiricism and its consequences Outline and investigate Kant’s theory of knowledge: Transcendental Idealism Discuss whether Kant’s theory overcomes Hume’s radical empiricism Conclude our investigation into the theory of knowledge Today’s Lecture

Recap: David Hume

David Hume • 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 • Impressions • Lively, Vivid Sensations • Ideas • Pale impressions / copies • All ideas are derived from impressions • All the mind possesses is a collection of perceptions

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

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 David Hume 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)

According to Hume we must abandon the following abstract concepts: • The concept of causation • We never perceive a necessary cause; only succession and contiguity • The self • When we reflect we never find a thinking thing; only many different perceptions • 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 David Hume

Kant

Outline: Lived 1724-1804 Represents an important turning point in epistemology Wrote the Critique of Pure Reason in response to Hume’s radical empiricism Immanuel Kant

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) Immanuel Kant

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 Immanuel Kant

Kant’s Theory of Knowledge

Kant’s Theory of Knowledge Kant’s understanding of ‘knowledge’ Analytic True by definition No relevance to reality Synthetic Not logically certain A Priori Independent of senses A Posteriori Derived from sense experience A Priori Independent of senses Universal Certain A Posteriori Derived from sense experience Specific Not certain

Activity: List any knowledge that corresponds to the following categories: • Synthetic a posterioriKnowledge • 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 Kant’s Theory of Knowledge Informative but not certain Certain but not informative Analytic a posterioriknowledge is not possible!

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 Kant’s theory of Knowledge Informative, not just true by definition Necessary & Universal For Example: Every event has a cause Substance exists The Self exists The big question is whether such knowledge exists!

Traditional theories of knowledge Kant’s Theory of Knowledge Traditional theories of knowledge are concerned with asking whether our idea of the apple corresponds to the apple itself

Kant’s Copernican Revolution Kant’s Theory of Knowledge Instead of asking how our knowledge conforms to objects in the world; Kant asks how objects in the world must conform to us

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’ • Unity • Plurality • Totality • Relations of substance and characteristics of substance • Relations of cause and effect • Relations of reciprocity Kant’s Theory of Knowledge

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 Kant’s Theory of Knowledge

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 Kant’s theory of Knowledge

Kant’s theory of Knowledge • 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

Conclusion to Topic

Topic Conclusion Kant’s Transcendental Idealism

Lecture 15: Certainty