Evidentialism

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EVIDENTIALISM

"Evidentialism" is the view about epistemic justification that identifies the extent to which a person is justified in believing a proposition with the extent to which the evidence the person has supports the truth of the proposition. Other doxastic attitudes such as withholding judgment and denying are also justified by the character of the person's evidence.

A full-scale evidentialist theory would explain what constitutes evidence, what it means to have a certain body of evidence, and what it means for a body of evidence to support a proposition to any given extent. Ordinarily, people count as evidence external things such as fingerprints and bank records. However, according to evidentialists, our fundamental evidence is constituted by our perceptual experiences, our apparent memories, and other mental states. A full-scale theory requires an account of what we have as this ultimate sort of evidence: It is unclear, for example, whether someone's unactivated memories are part of the person's current evidence. The evidential support relation to which evidentialists appeal is not a familiar logical relation. Perceptual states can support beliefs about the external world, yet there is no familiar logical relation between those states and the beliefs they support. Furthermore, one's evidence on its own does not support its distant and unnoticed logical consequences. A complete evidentialist theory would clarify the justifying connection between a body of evidence and a proposition.

Leading skeptical controversies are usefully understood to concern what sort of evidence is required for knowledge. For example, if knowledge requires complete epistemic justification, and this requires having entailing evidence, then skeptics can cogently argue that we have no such evidence for any empirical proposition and that therefore we have no empirical knowledge. On the other hand, standard skeptical arguments fail if nonentailing evidence can completely justify belief. An evidentialist theory can resolve this dispute either way.

Diverse theories of justification can be understood as evidentialist views that differ on the nature of evidence, its possession, and how it supports belief. For instance, a typical coherentist theory in effect holds that a person has her beliefs as evidence and that support by evidence consists in coherence with it. A typical foundationalist theory in effect holds that justified beliefs must include some that are defended by a foundational sort of evidence—for example, by perceptual states—and that this evidence is had by the person by being consciously accessible.

Evidentialism entirely discounts factors that figure centrally in some theories of justified belief. These factors include the intellectual pedigree of the belief, the believer's capacity or intention to fulfill intellectual duties or to exemplify cognitive virtues, and the normal functioning of the operative belief-forming mechanism. Justifying evidence for a belief might happen to arise in an irresponsibly haphazard inquiry with no attempt to fulfill any epistemic duty, as a fluke result of some abnormal cognitive activity lacking in intellectual virtue. The evidentialist view is that regardless of all this, belief is justified because the evidence possessed supports the proposition.