I examine two strands in Locke's thought which seem to conflict with his corpuscularian sympathies: his repeated suggestion that natural philosophy is incapable of being made a science, and his claim that some of the properties of bodies--secondary qualities, powers of gravitation, cohesion and maybe even thought--are arbitrarily "superadded" by God. ;Locke often says that a body's properties flow from its real essence as the properties of a triangle flow from its definition. He is widely read as having thought that (...) if we had ideas of a body's real essence, we would be able to perceive a priori a necessary connection between that body's real essence and its observable properties. I argue that this leaves Locke's skepticism without any rationale, making it depend entirely upon our ignorance of corpuscular structures when in fact he never rules out the possibility of our acquiring ideas of corpuscular structures through improvements in microscopy. I argue that Locke's geometrical analogy is better understood as an endorsement of deductivism about scientific explanation. He thinks that knowledge of corpuscular structures is a necessary, but not a sufficient, condition for scientific knowledge of bodies. The deeper source of his skepticism is his view that we cannot have universal and certain knowledge of the laws of nature because they are contingent. ;I approach the subject of Locke's attitude toward mechanism by examining his superaddition doctrine. In contrast with M. R. Ayers, I attribute to Locke what I call strong voluntarism: the view that a body's powers to interact with other bodies are not fully determined by the essence of matter, and that they are at least partly determined by the will of God. I argue that Descartes and Boyle are also strong voluntarists, but that Locke's voluntarism differs in that he maintains that bodies have some powers which are not even partly explicable in terms of the motions of matter. Locke's position is thus incompatible with the mechanism of Descartes and Boyle. (shrink)