While Newtonian epistemology admitted of many variations, at its core rested a new skepticism about the validity of apriori rationalist accounts of nature and a new assertion of brute empirical fact as a valid philosophical understanding in its own right. European Natural philosophers in the second half of the seventeenth century had thrown out the metaphysics and physics of Aristotle with its four part causality and teleological understanding of bodies, motion and the cosmic order. In its place, however, a new mechanical causality was introduced that attempted to explain the world in equally comprehensive terms through the mechanisms of an inert matter acting by direct contact and action alone. This approach lead to the vortical account of celestial mechanics, a view that held material bodies to be swimming in an ethereal sea whose action pushed and pulled objects in the manner we observe. What could not be observed, however, was the ethereal sea itself, or the other agents of this supposedly comprehensive mechanical cosmos. Yet rationality nevertheless dictated that such mechanisms must exist since without them philosophy would be returned to the occult causes of the Aristotelian natural tendencies and teleological principles. Figuring out what these point-contact mechanisms were and how they worked was, therefore, the charge of the new mechanical natural philosophy of the late seventeenth century. Figures such as Descartes, Huygens, and Leibniz established their scientific reputations through efforts to realize this goal.