Infinitism

Infinitism is the view that knowledge may be justified by an infinite chain of reasons. It belongs to epistemology, the branch of philosophy that considers the possibility, nature, and means of knowledge.

Since Gettier, "knowledge" is no longer widely accepted as meaning "justified true belief". However, some epistemologists still consider knowledge to have a justification condition. Traditional theories of justification (foundationalism and coherentism) and indeed some philosophers consider an infinite regress not to be a valid justification. In their view, if A is justified by B, B by C, and so forth, then either

Infinitism, the view, for example, of Peter D. Klein, challenges this consensus, referring back to work of Paul Moser (1984) and John Post (1987). In this view, the evidential ancestry of a justified belief must be infinite and non-repeating, which follows from the conjunction two principles that Klein sees as having straightforward intuitive appeal: "The Principle of Avoiding Circularity" and "The Principle of Avoiding Arbitrariness."

The Principle of Avoiding Circularity (PAC) is stated as follows: "For all x, if a person, S, has a justification for x, then for all y, if y is in the evidential ancestry of x for S, then x is not in the evidential ancestry of y for S." PAC says that the proposition to be justified cannot be a member of its own evidential ancestry, which is violated by coherence theories of justification.

The Principle of Avoiding Arbitrariness (PAA) is stated as follows: "For all x, if a person, S, has a justification for x, then there is some reason, r1, available to S for x; and there is some reason, r2, available to S for r1; etc." PAA says that in order to avoid arbitrariness, for any proposition x to be justified for an epistemological agent, there must be some reason r available to the agent; this reason will in turn require the same structure of justification, and so on ad infinitum. Foundationalist theories can only avoid arbitrariness by claiming that some propositions are self-justified. But if a proposition is its own justification (e.g. coherentism), then it is a member of its own evidential ancestry, and the structure of justification is circular.

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