  Two general constraints on definitions are particularly relevant to definitions of art. First, given that accepting that something is inexplicable is generally a philosophical last resort, and granting the importance of extensional adequacy, list-like or enumerative definitions are if possible to be avoided. Enumerative definitions, lacking principles that explain why what is on the list is on the list, don’t, notoriously, apply to definienda that evolve, and provide no clue to the next or general case (Tarski’s definition of truth, for example, is standardly criticized as unenlightening because it rests on a list-like definition of primitive denotation; see Field 1972; Devitt 2001; Davidson 2005).  Corollary: when everything else is equal (and it is controversial whether and when that condition is satisfied in the case of definitions of art), non-disjunctive definitions are preferable to disjunctive ones. Second, given that most classes outside of mathematics are vague, and that the existence of borderline cases is characteristic of vague classes, definitions that take the class of artworks to have borderline cases are preferable to definitions that don’t (Davies 1991 and 2006; Stecker 2005).