|Abstract:||This article adopts the perspective of Optimality Theory (OT) to address the question whether phonology and syntax are equally autonomous. We show that OT enjoys the same advantages and encounters the same problems in syntax as in phonology; this suggests that markedness plays an equally important role in both components of language. Most markedness constraints, however, are clearly grounded: although they refer to specifically linguistic categories (self-containment), they typically display some degree of functional adaptation to the demands of performance (nonarbitrariness). In consequence, phonology and syntax should be expected to be grounded to a similar degree. Pace Hale & Reiss (2000), however, the postulation of grounded markedness constraints in the theory of grammar does not violate Ockham's Razor. In particular, we show that markedness cannot be equated with performance difficulty, and we demonstrate that infants require knowledge of markedness during language acquisition in order to transcend the limitations of inductive generalization. However, this does not necessarily imply that knowledge of markedness is innate; we argue, rather, that most markedness constraints may in fact emerge in the course of linguistic development through the child's monitoring of her own performance.