The view in epistemology that follows the suggestion that a subject may know a proposition p if

1. (i) p is true;

2. (ii) the subject believes p; and

3. (iii) the belief that p is the result of some reliable process of belief formation.

The third clause is an alternative to the traditional requirement that the subject be justified in believing that p, since a subject may in fact be following a reliable method without being justified in supposing that she is, and vice versa. For this reason, reliabilism is sometimes called an externalist approach to knowledge: the relations that matter to knowing something may be outside the subject’s own awareness. As the suggestion stands, it is open to counterexamples: a belief may be the result of some generally reliable process which was in fact malfunctioning on this occasion, and we would be reluctant to attribute knowledge to the subject if this were so, although the definition would be satisfied (see also Gettier examples). Reliabilism pursues appropriate modifications to avoid the problem without giving up the general approach.