Reliabilism is an approach to the analysis of either knowledge or justified belief that makes, in some way or another, the reliability of belief-producing faculties or processes the key notion of epistemic assessment. An early version of a reliabilist theory of knowledge was proposed by David M. Armstrong (1973), who thought of knowledge in terms of a reliable thermometer that accurately indicates the correct temperature. A (noninferential) true belief amounts to knowledge, according to Armstrong, if its properties nomically (i.e., via the laws of nature) guarantee its truth. Closely related theories conceive of knowledge as resulting from a counterfactual guarantee of truth. For instance, according to Robert Nozick (1981), knowledge comes about when a subject's belief that p tracks the truth of p, which it does (focusing just on the core of Nozick's theory) if the following condition is met: S would not believe that p if p were...