Warrant and Proper Function

Plantinga distinguishes warrant from justification to shift the epistemological question away from deontological obligation and toward the conditions that actually make true belief knowledge. Justification, in the internalist tradition Plantinga rejects, concerns whether a believer has fulfilled epistemic duties or has adequate evidence. Warrant, by contrast, is the property that converts true belief into knowledge, and it is external: the believer need not have cognitive access to it. A belief has warrant, on Plantinga's view, when it is produced by cognitive faculties functioning properly in a congenial environment according to a design plan aimed at truth . This means a person can know something without knowing that they know it, or being able to demonstrate that their faculties are functioning properly.

In the eleventh chapter, Plantinga argues that the notion of proper function—along with related concepts like purpose, malfunction, and design plan—resists any satisfactory naturalistic analysis. He considers proposals from John Pollock, Ruth Millikan, and John Bigelow and Robert Pargetter, and finds each inadequate . The core problem is that proper function seems to require a normative standard: a heart can function properly or malfunction, but the difference is not merely statistical frequency. If naturalism cannot account for this normativity, then anyone convinced that proper function is real has a powerful argument against naturalism. Plantinga does not claim to prove naturalism false, but he argues that the epistemic naturalist who relies on proper function is implicitly committed to a supernaturalist metaphysics that can ground it.

Warrant and Proper Function marks a significant shift from Plantinga's earlier Reformed epistemology. In works like 'Reason and Belief in God,' his strategy was to argue that belief in God could be properly basic and thus rationally permissible without propositional evidence, challenging classical foundationalism's criteria for what belongs in the foundations of a noetic structure. In the Warrant trilogy, he moves from permissibility to a positive account of knowledge: the question is no longer whether theistic belief is allowed in the foundations, but whether any belief can constitute knowledge without externalist warrant conditions . This is a more ambitious project, because it implies that evidentialist objections to religious belief fail not merely because evidentialism is too strict, but because no internalist account of knowledge succeeds.

The design plan is the specification of how a cognitive faculty is supposed to work: what it is for, what conditions it requires, and what counts as success. Plantinga uses the analogy of artifacts and organs: a heart has a function, and it can succeed or fail relative to that function. Cognitive faculties are analogous, and warrant depends on whether they are operating according to their design plan . The controversy is that 'design plan' carries teleological implications that many naturalists reject. Plantinga embraces this: he argues that the notion is indispensable to epistemology and that naturalism cannot accommodate it. Critics reply that teleology can be naturalized through evolutionary function or that Plantinga's reliance on design smuggles in theism at the foundations of his epistemology. The debate turns on whether proper function is a genuine feature of the world or a useful fiction.

Warrant and Proper Function is the second volume of a trilogy, preceded by Warrant: The Current Debate (1993) and followed by Warranted Christian Belief (2000). The first volume surveys and critiques contemporary accounts of warrant, including internalism and various forms of reliabilism; the second develops Plantinga's own proper functionalist alternative; the third applies it to Christian belief through the extended A/C model . The publisher and reviewers note that the second volume does not presuppose the arguments of the first and can stand alone as a contribution to epistemology . However, readers who want the full force of Plantinga's critique of rival views should read both 1993 volumes, and those interested in the religious payoff will need the 2000 volume.

The most common misunderstanding is that Plantinga argues evolutionary theory is false, or that evolution cannot produce reliable cognitive faculties. Neither is his claim. His argument in the twelfth chapter is that metaphysical naturalism combined with contemporary evolutionary accounts of human origins is self-defeating: if our beliefs are produced by faculties selected solely for reproductive fitness, and if fitness is not correlated with truth, then we have an undefeated defeater for trusting our cognitive faculties in general—including the faculty that produced the belief in naturalism itself . Plantinga does not say evolution is false; he says naturalism plus evolution undermines the warrant for believing naturalism. Critics have challenged whether the fitness–truth correlation is as weak as Plantinga suggests, but the argument is not an attack on biology.