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Intro to Philosophy Unit 3: Knowledge and Skepticism (Epistemology)

Epistemology asks what knowledge is, where it comes from and whether we have any. This unit covers the definition of knowledge, the rationalist and empiricist traditions, and the major skeptical challenges with replies to them.

Covers: Knowledge as justified true belief, Gettier problems, Rationalism and empiricism, Descartes' method of doubt, A priori, a posteriori, analytic and synthetic, Hume's problem of induction, Theories of justification and replies to skepticism

Study guide

The traditional analysis says a person knows a claim P when P is true, the person believes P, and the person is justified in believing it: justified true belief. In 1963 Edmund Gettier offered short cases where someone has a justified true belief that is true only by luck, and most readers agree it is not knowledge. In one, Smith believes 'the man who will get the job has ten coins' because he has evidence Jones will get the job and has ten coins; in fact Smith gets the job and happens to have ten coins. Gettier cases launched decades of attempts to add a fourth condition, such as 'no false lemmas,' or to replace justification with reliability.

Where does knowledge come from? Rationalists such as Descartes, Spinoza and Leibniz argue that reason can give substantive knowledge, sometimes through innate ideas. Empiricists such as Locke, Berkeley and Hume argue that all ideas come from experience; Locke called the newborn mind a tabula rasa. Useful distinctions help here. A priori knowledge is justified independently of experience; a posteriori knowledge depends on it. An analytic statement is true by meaning, like 'all bachelors are unmarried'; a synthetic statement adds information, like 'the cat is on the mat.' Kant argued that some knowledge, such as mathematics and the principle that every event has a cause, is synthetic a priori, because the mind supplies the forms that structure experience.

Descartes' Meditations uses methodical doubt to find a certain foundation. Our senses sometimes deceive us; we might be dreaming; and an evil demon might deceive us even about arithmetic. Yet one thing survives: while I doubt, I must exist, so 'I think, therefore I am.' Descartes then argues that God exists and is no deceiver, so whatever he perceives clearly and distinctly is true. Critics call this the Cartesian circle, since he relies on clear perception to prove God and on God to trust clear perception. Berkeley took empiricism toward idealism, arguing that objects are collections of ideas: to be is to be perceived.

Hume raised the problem of induction. Every inference from past to future assumes that nature is uniform, but that assumption cannot be proven by reason, since its denial is not contradictory, or by experience without arguing in a circle. Hume concluded that custom, not reason, leads us to expect the sun to rise. Theories of justification address the regress problem: foundationalists stop the chain of reasons with basic beliefs, coherentists say beliefs are justified by fitting together, and reliabilists such as Goldman say a belief is justified if produced by a reliable process. Against skeptics, G. E. Moore argued that he is more certain he has hands than he is of any skeptical premise, while others deny the closure principle the skeptic needs.

Key ideas

• Knowledge has traditionally been analyzed as justified true belief, but Gettier cases show this is not sufficient.
• Rationalists stress reason and innate ideas; empiricists stress experience as the source of all ideas.
• A priori and a posteriori concern how a claim is known; analytic and synthetic concern what makes it true.
• Descartes' methodical doubt ends at the cogito, which he uses with God's existence to rebuild knowledge.
• Hume argued that induction cannot be rationally justified, though custom makes us rely on it.
• Kant held that the mind structures experience, making synthetic a priori knowledge possible.
• Foundationalism, coherentism and reliabilism give rival answers to how beliefs are justified.

Formulas and rules

Common mistakes

• Treating a priori and analytic as the same thing, which ignores Kant's synthetic a priori.
• Saying Gettier cases involve false beliefs; the target belief in a Gettier case is true.
• Claiming Hume thought we should stop making predictions, when he said custom makes us keep doing so.
• Mixing up rationalists and empiricists, such as calling Locke a rationalist.
• Forgetting that Descartes doubts as a method to reach certainty, not because he is a committed skeptic.

Before the test, make sure you can

• Explain the justified true belief analysis and how a Gettier case challenges it.
• Contrast rationalism and empiricism and name the main figures of each.
• Classify statements as analytic or synthetic and as a priori or a posteriori.
• Trace the steps of Descartes' method of doubt to the cogito.
• Explain the Cartesian circle objection.
• State Hume's problem of induction and his response.
• Compare foundationalism, coherentism and reliabilism.
• Describe Moore's and the closure-denial responses to skepticism.

Words to know

Epistemology

The study of knowledge, justification and belief.

Justified true belief

The traditional analysis of knowledge: a belief that is true and justified.

Gettier case

An example where someone has a justified true belief that is true by luck, so it seems not to be knowledge.

Rationalism

The view that reason can give knowledge of the world independent of experience; Descartes, Spinoza, Leibniz.

Empiricism

The view that all ideas and knowledge of the world come from experience; Locke, Berkeley, Hume.

Tabula rasa

Locke's 'blank slate' description of the mind at birth.

A priori

Known independently of experience.

A posteriori

Known through experience.

Analytic statement

A statement true by the meanings of its terms.

Synthetic statement

A statement that adds information beyond the meaning of its terms.

Cogito

Descartes' 'I think, therefore I am,' the one belief that survives his doubt.

Evil demon

Descartes' imagined deceiver used to doubt even mathematics.

Problem of induction

Hume's argument that inferences from past to future cannot be justified without assuming nature is uniform.

Idealism

Berkeley's view that objects exist only as ideas in minds: to be is to be perceived.

Foundationalism

The view that justified beliefs rest on basic beliefs that need no further support.

Coherentism

The view that beliefs are justified by how well they fit together in a system.

Reliabilism

The view that a belief is justified if it comes from a reliable belief-forming process.

Closure principle

If you know P and know P implies Q, you know Q; used in skeptical arguments.

Sample practice questions

30 more questions like these, from level 1 to 5, are in the practice set.