 Wolff’s rationalist metaphysics is characteristic of the Enlightenment by virtue of the pretensions of human reason within it, not by reason’s success in establishing its claims. Much the same could be said of the great rationalist philosophers of the seventeenth century. Through their articulation of the ideal of scientia, of a complete science of reality, composed of propositions derived demonstratively from a priori first principles, these philosophers exert great influence on the Enlightenment. But they fail, rather spectacularly, to realize this ideal. To the contrary, what they bequeath to the eighteenth century is metaphysics, in the words of Kant, as “a battlefield of endless controversies.” However, the controversies themselves – regarding the nature of God, mind, matter, substance, cause, et cetera, and the relations of each of these to the others – provide tremendous fuel to Enlightenment thought.