Foundationalism

Knowledge is more than true belief. True beliefs that come from just lucky guesswork do not qualify as knowledge. Knowledge requires that the satisfaction of its belief condition be appropriately related to the satisfaction of its truth condition. In other words, knowledge requires a justification condition. A knower must have an adequate indication that a known proposition is true. A traditional view, suggested by Plato (c. 428–348 or 347 B.C.E.) and Immanuel Kant (1724–1804), proposes that this adequate indication consists of evidence indicating that a proposition is true. This view requires that true beliefs qualifying as knowledge be based on justifying evidence, or reasons.

When reasons are beliefs, we have inferential justification: one belief is justified on the basis of another belief. How is the latter, supporting belief itself justified? Is another supporting belief always needed? According to foundationalism, another supporting belief is not always needed.