This paper examines some of the implications of a pivotal theoretical distinction between linguistic rules and nonrules. The difference between the two types of warrants may be represented by a difference in illocutionary force and in epistemic status. Whereas rules may make claims to truth, to felicity, or to appropriateness, nonrules make claims to plausibility. An explication then focuses on motivating the choice of plausibility as the epistemic criterion. Finally, Rescher's (1976) system of plausible reasoning demonstrates how Sperber and Wilson's (1986) conception of pragmatic relevance, a nonrule, may act as an authorizing warrant to sanction plausibility values.