The principle that the universe is a plenum has two interesting consequences for Leibniz’s conception of matter. First, if there is no void, then everything is full of matter and there are no ultimate atoms of the substantial world, and thus matter should be infi nitely divisible. Second, if there is no void, then there is no action-at-a-distance and thus (Newtonian) universal gravitation is not acceptable within the framework of this system. This chapter discusses these two consequences of Leibniz’s explicit denial of the existence of void.