This chapter explores the nature of syntactic competence -- what it means to ‘know’ a language. It asks how generative grammar has been used to model competence. After discussing the difference between prescriptive and descriptive rules, we describe procedures for discovering descriptively adequate rules. We distinguish inductive from deductive grammars, the latter of which are associated with classical transformational models of grammar, according to which human languages have all and only those (structural) properties that are expressible in the transformational formalism and the former of which are associated with constraint-based views of grammar, according to which an expression is syntactically well-formed if its form is paired with its meaning as an instance of some grammatical construction. It is this construction-based view of grammar that we adopt in this book. Construction Grammar offers an enriched model of grammatical competence, which attempts to capture all of the linguistic routines that an adult native speaker knows. In Construction Grammar, grammar represents an array of form-meaning-function groupings of varying degrees of productivity and internal complexity.