In epistemology, the philosophical study of knowledge, a central issue is the justification of knowledge: how beliefs are supported, validated, or grounded. The justification problem addresses the logical structure that connects beliefs to truth and seeks to answer how individuals can claim to know something rather than merely believe it. In this context, three major theories have emerged: Foundationalism, Coherentism, and Anti-Foundationalism. These theories offer distinct models of the structure and justification of knowledge, reflecting deep philosophical divisions regarding the nature of epistemic support and rational belief.

Foundationalism

Foundationalism is a theory that claims that all justified beliefs are either basic beliefs or derived beliefs. Basic (or foundational) beliefs are self-justified, indubitable, or justified independently of any other beliefs. Derived (or non-basic) beliefs, by contrast, are justified by their logical or inferential relationship to foundational beliefs. Foundationalism seeks to avoid infinite regress in justification by positing a secure base from which all other justified beliefs arise, thus ensuring a hierarchical structure of knowledge.

Classical foundationalism, associated with philosophers such as René Descartes, holds that foundational beliefs must be certain, self-evident, or incorrigible. Cartesian foundationalism uses methodological skepticism to reject all beliefs that can be doubted, leaving only the cogito (“I think, therefore I am”) as an indubitable foundation. Other candidates for foundational beliefs include sense data, analytic truths, and logical axioms. Foundationalism assumes that unless beliefs rest on an epistemically secure foundation, knowledge becomes unstable or unjustified.

In modern foundationalism, the strict requirement for certainty is often relaxed. Rather than requiring absolute certainty, foundationalists may argue for beliefs that are prima facie justified or non-inferentially warranted. Examples include perceptual beliefs (“I see a tree”), memory beliefs (“I recall eating breakfast”), and introspective beliefs (“I feel pain”). These beliefs serve as the epistemic bedrock upon which higher-level beliefs (e.g., scientific theories, moral judgments) are built.

Foundationalism faces challenges, including the problems of specifying what qualifies as a foundational belief, whether such beliefs can truly be self-justified, and how they can provide adequate support for more complex or abstract beliefs. Nevertheless, foundationalism remains influential in many schools of thought, including analytic philosophy, empiricism, and rationalism, due to its clear structure and response to the regress problem.