Leibniz argues against Descartes’s conception of material substance based on considerations of unity. I examine a key premise of Leibniz’s argument, what I call the Plurality Thesis—the claim that matter (i.e. extension alone) is a plurality of parts. More specifically, I engage an objection to the Plurality Thesis stemming from what I call Material Monism—the claim that the physical world is a single material substance. I argue that Leibniz can productively engage this objection based on his view that matter is (...) discrete. The discreteness of matter provides two aspects of support for the Plurality Thesis. First, it indicates that the parts of matter do not share boundaries and are, therefore, independent in an important sense. Second, it indicates that the parts of matter are determinate and are, therefore, ontologically prior to the wholes they compose. (shrink)

Leibniz's World-Apart Doctrine states that every created substance is independent of everything except God. Commentators have connected the independence of substance asserted by World-Apart to a variety of important aspects of Leibniz's modal metaphysics, including his theory of compossibility and his notion of a possible world (including what possible worlds there are). But what sort of independence is at stake in World-Apart? I argue that there is not a single sense of "independence" at stake, but at least three: what I (...) call "causal", "phenomenal", and "ontological" independence. Further, I distinguish two versions of each type of independence: what I call "basic" and "strict" versions. I argue that only basic versions can be legitimately attributed to Leibniz. In light of this result, I conclude, pace previous commentators, that World-Apart has little impact on Leibniz's modal metaphysics. (shrink)

This chapter discusses Gottfried Wilhelm Leibniz’s philosophical reflections on mind and body. It first considers Leibniz’s distinction between substance and aggregate, referring to the former as a being that must have true unity (what he calls unum per se) and to the latter as simply a collection of other beings. It then describes Leibniz’s extension of the term “substance” to monads and other things such as animals and living beings. It also examines Leibniz’s views about the union of mind and (...) body, whether mind and body interact, and how interaction is related to union. More specifically, it asks whether mind and body together constitute an unum per se and analyzes Leibniz’s account of the per se unity of mind-body composites. In addition, the chapter explores the problem of soul-body union as opposed to mind-body union and concludes by discussing Leibniz’s explanation of soul-body interaction using a system of pre-established harmony. (shrink)