Internalism and Externalism in Epistemology

The internalism/externalism distinction in epistemology applies to both theories of justification and theories of knowledge. The distinction is most clearly defined for theories of justification. An internalist theory of epistemic justification is any theory that maintains that epistemic justifiedness is exclusively a function of states internal to the cognizer. Externalism is the denial of internalism. Thus, an externalist theory is any theory that maintains that epistemic justifiedness is at least partly a function of states or factors external to the cognizer, i.e., states or factors outside the cognizer’s ken. There is no unified agreement among internalists as to which internal states are epistemically relevant, and different internalisms emerge based on the subset of internal states deemed relevant. (See Internalism and Justification for details.) Internalists typically maintain that justification is a normative notion in the belief-guiding/regulative sense. Internalists also typically maintain that one can tell whether one is justified in believing p simply by reflecting on one’s internal evidence for p. The central internalist intuition, as highlighted by the New Evil Demon Problem is this: There can be no difference in justification without a difference in epistemically relevant internal states. Externalism is motivated by the intuition that epistemic justification must be conceptually connected to truth such that the conditions that make a belief justified also make it objectively probable. Externalists are also typically motivated by the view that children and animals can form justified beliefs, while failing to satisfy the internalist’s intellectualist requirements for justification. The dominant externalist theory of justification is process reliabilism, a simplified version of which holds that a belief is justified iff it’s produced by a reliable process. There is less canonical agreement when it comes to applying the internalist/externalist distinction to theories of knowledge. In one sense, every plausible epistemology is an externalist theory because every plausible epistemology requires an externalist truth condition and an externalist Gettier-blocking fillip. However, in another widely used sense, “externalist” theories of knowledge are theories that replace the internalist justification condition with either an externalist justification condition or some other externalist constraint (such as a causal or modal constraint); while “internalist” theories of knowledge hold that internalist justification is necessary for knowledge and also typically hold that no other kind of justification is needed for knowledge, though they do incorporate some sort of externalist constraint to handle the Gettier problem.