Through its focus on the semantic, rather than the syntactic axis of bibliographic classification systems, Beghtol's 1986 article on four perspectives of warrant provides us with a set of conceptual tools that can be used to understand, analyze, evaluate and design any knowledge-representation system. In this way warrant, as a concept, joins the ranks of relevance as a pivotal notion, offering a lens for contextualizing the meanings and uses to which ever-evolving classifications are put. With reference to examples, this paper concludes by invoking Beghtol's warrant as a means for systematically evaluating how legacy and emerging classification systems measure up to their mandates.