The most significant development in religious epistemology at the beginning of the new millennium was the completion of Alvin Plantinga's trilogy on warrant and religious knowledge. Plantinga's earlier work on Reformed epistemology focuses on the question of whether religious beliefs can be justified, in the sense that they can be accepted without violating any epistemic duties. His later work is concerned with warrant, defined as that which, added to true belief, enables such belief to qualify as knowledge. Plantinga argues convincingly that warrant is distinct from justification and also from rationality, in any of the several senses of the latter term. His own view is most akin to reliabilism, but he argues that standard versions of reliabilism face debilitating objections, and comes out instead for a definition of warrant in terms of the proper functioning of a person's epistemic faculties.

For these faculties to...