The epistemic regress argument shows that any attempt to justify a belief by appeal to another belief faces a trilemma: justify that second belief (beginning an infinite regress), treat it as foundational (abandoning the demand for justification), or accept circular justification (begging the question). This argument provides the logical structure motivating foundationalism, coherentism, and infinitism as distinct systematic responses. Understanding regress structure is essential for evaluating all theories of justification.
Formalize the trilemma: justifying belief B1 requires B2, justifying B2 requires B3, etc., leading to infinite regress (problematic), circular reasoning, or foundational beliefs. Map how each epistemological theory responds.
The regress problem you have already encountered identifies a pressing puzzle: if every justified belief requires justification from another belief, we face an infinite chain. The epistemic regress argument formalizes this puzzle into a trilemma that confronts anyone who holds that justification requires evidential support. Understanding the argument's structure — not just the problem it names — is the key to evaluating the competing theoretical responses that dominate epistemology.
Here is the argument laid out formally. Suppose you believe P, and someone asks you why. You offer justifying belief B1. They ask why you believe B1. You offer B2. And so on. This chain must end somewhere, and only three endings are available: (1) the chain is infinite, with each belief justified by another ad infinitum; (2) the chain is circular, eventually returning to a belief that was supposed to be justified; or (3) the chain terminates at some belief that is not itself justified by another belief — a foundational stopping point. These are the three horns of the trilemma, and each corresponds to a school of epistemology: infinitism (option 1), coherentism in its circular form (option 2), and foundationalism (option 3).
The argument is often misread as simply establishing that foundationalism is correct — as if the regress eliminates all other options. But understanding the structure reveals that each horn is a genuine, defensible position. Foundationalism (which you have studied) responds by positing basic beliefs — beliefs justified by non-doxastic sources like perception, memory, or rational intuition — that stop the regress at a terminus. Coherentism responds by rejecting the linear chain metaphor: justification is not a chain at all but a web, where each belief is supported by its coherence with the whole. Circularity is only a problem on the chain model; on the web model, beliefs support each other mutually without vicious circularity. Infinitism (associated with Peter Klein) argues that an infinite chain of reasons is not problematic as long as the reasons are available, even if not all consciously entertained simultaneously.
The practical upshot is that the regress argument is a diagnostic tool: it identifies exactly what any adequate theory of justification must explain. Every epistemological theory is, in part, a response to this trilemma — a choice about which horn to accept and a story about why that horn is not as bad as it initially seems. When you encounter a new theory of justification, the first question to ask is: how does it address the regress? Does it posit foundational beliefs? Holistic coherence? Infinitely available reasons? The regress argument maps the logical space of possible theories and makes it possible to evaluate them systematically.
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