 Philosophical rationalism can be understood to involve any or all of the following: commitment to the existence of innate ideas or principles, the privileging of a priori cognition to cognition known a posteriori, and endorsement of the principle of sufficient reason (PSR). Even though Wolff is officially agnostic regarding innate ideas, a priori cognition (at least in the traditional sense of a cognition from grounds) enjoys a privileged place in his system, and to be sure, PSR is central to Wolff’s entire exposition of metaphysics and figures prominently in all levels of his philosophical system. Wolff is, accordingly, correctly identified as a philosophical rationalist; yet, this label has often inspired misleading characterizations of Wolff’s thought as abjuring all reliance upon experience in the aim of constructing a pure intellectual system founded solely on the principle of contradiction. Such a caricature, however persistent, is to be firmly rejected on both historical and philosophical grounds.