Epistemology
Epistemology examines knowledge, justification, belief, truth, and the sources and limits of knowledge. GCE questions typically ask you to analyse the tripartite account, explain Gettier cases, compare rationalism and empiricism, and assess sceptical challenges.
Knowledge as justified true belief
The standard analysis holds that S knows that p only if (i) S believes p, (ii) p is true, and (iii) S is justified in believing p. Each condition is necessary; together they were long thought sufficient. Gettier-style cases challenge sufficiency by making justified true belief depend on luck. Responses include adding a no-false-grounds condition, a causal condition, or a reliabilist condition.
Sources and justification
Perception, reason, memory, testimony and introspection are candidate sources. Rationalism (Descartes, Leibniz) holds that reason can yield substantive knowledge independently of experience; empiricism (Locke, Berkeley, Hume) traces knowledge to experience. A priori knowledge is independent of experience; a posteriori depends on it. Analytic propositions are true by meaning; synthetic propositions extend knowledge. Foundationalism grounds justification in basic beliefs; coherentism requires mutual support among beliefs; reliabilism requires that beliefs be produced by reliable processes.
Truth
Correspondence theory says truth is agreement with reality; coherence theory says truth is membership in a coherent system; pragmatic theory says true beliefs are those that work in practice. These are theories of truth, not merely of justification.
Worked example
Smith has strong evidence that Jones will get a job and that Jones has ten coins in his pocket. Smith infers: 'The person who will get the job has ten coins in his pocket.' Unknown to Smith, he himself will get the job and he too has ten coins. The belief is true, believed, and justified by the evidence. Yet Smith does not know it: his justification supports a different person's case, and truth is reached by accident. The example shows JTB is not sufficient; justification must be appropriately connected to truth.
Traps
A justified false belief is not knowledge, and a true belief held for bad reasons is not knowledge. Scepticism is not simply 'doubting everything': Descartes uses methodical doubt to find certainty, while Hume defends mitigated scepticism. Do not confuse coherence as a test of justification with coherence as a definition of truth. A priori does not mean innate, and a posteriori does not mean 'after birth' in a trivial sense.