Justification, epistemic
Authors: Foley Richard 
Published: September 2018

The term ‘justification’ belongs to a cluster of normative terms that also includes ‘rational’, ‘reasonable’ and ‘warranted’. All these are commonly used in epistemology, but there is no generally agreed way of understanding them, nor is there even agreement as to whether they are synonymous. Some epistemologists employ them interchangeably; others distinguish among them. It is generally assumed, however, that belief is the target psychological state of these terms; epistemologists are concerned with what it takes for a belief to be justified, rational, reasonable or warranted. Propositions, statements, claims, hypotheses and theories are also said to be justified, but these uses are best understood as derivative; to say, for example, that a theory is justified for an individual is to say that were that individual to believe the theory (perhaps for the right reasons), the belief would be justified.
Historically, the two most important accounts of epistemic justification are foundationalism and coherentism. Foundationalists say that justification has a tiered structure; some beliefs are self-justifying, and other beliefs are justified in so far as they are supported by these basic beliefs. Coherentists deny that any beliefs are self-justifying and propose instead that beliefs are justified in so far as they belong to a system of beliefs that are mutually supportive. Most foundationalists and coherentists are internalists; they claim that the conditions that determine whether or not a belief is justified are primarily internal psychological conditions (for example, what beliefs and experiences one has). In the last quarter of the twentieth century, externalism emerged as an important alternative to internalism. Externalists argue that one cannot determine whether a belief is justified without looking at the believer’s external environment. The most influential form of externalism is reliabilism.
Another challenge to traditional foundationalism and coherentism comes from probabilists, who argue that belief should not be treated as an all-or-nothing phenomenon: belief comes in degrees. Moreover, one’s degrees of beliefs, construed as subjective probabilities, are justified only if they do not violate any of the axioms of the probability calculus. Another approach is proposed by those who advocate a naturalization of epistemology. They fault foundationalists, coherentists and probabilists for an overemphasis on a priori theorizing and a corresponding lack of concern with the practices and findings of science. The most radical naturalized epistemologists recommend that the traditional questions of epistemology be recast into forms that can be answered by science.
An important question to ask with respect to any approach to epistemology is, ‘what implications does it have for scepticism?’ Some accounts of epistemic justification preclude, while others do not preclude, one’s beliefs being justified but mostly false. Another issue is the degree to which the beliefs of other people affect what an individual is justified in believing. All theories of epistemic justification must find a way of acknowledging that much of what each of us knows derives from what others have told us. However, some epistemologists insist that the bulk of the history of epistemology is overly individualistic and that social conditions enter into questions of justification in a more fundamental way than standard accounts acknowledge.