  This article examines questions connected with the two salient features noted, and in connection with the first, it also examines Locke’s relationship to Newton, a figure instrumental to the changing conceptions of scientific knowledge. Section 2 addresses questions connected to those changing conceptions. What does Locke take science (scientia) or scientific knowledge to be generally, why does he think that scientia in natural philosophy is beyond the reach of human beings, and what characterizes the conception of human knowledge in natural philosophy that he develops? Section 3 addresses the question provoked by Locke’s apparently conflicting treatments of the corpuscular hypothesis. Does he accept or defend the corpuscular hypothesis? If not, what is its role in his thought, and what explains its close connection to key theses of the Essay? Since a scholarly debate has arisen about the status of the corpuscular hypothesis for Locke, Section 3 reviews some main positions in that debate. Section 4 considers the relationship between Locke’s thought and Newton’s. All citations of An Essay Concerning Human Understanding are indicated by ‘E’, followed by the book and section numbers. Page numbers referring to the Nidditch edition are also provided.