The title of this volume is Vanishing Matter and the Laws of Motion. The context is the early modern debate over how best to revise or replace the Aristotelian account of individual bodies as the things of which the world is constituted. In the context of Newtonian mechanics, the phrase “vanishing matter” refers to the view that this theory provided a dynamical account of the behavior of large-scale material bodies, while at the same time treating them as mathematical entities and providing no insight into their nature. There is something right about this: Newtonian mechanics enables us to treat the behavior of bodies without fi rst saying anything about their metaphysical nature. This signals an important shift in the relationship between dynamics and matter theory. However, the phrase “vanishing matter” implies the vanishing of matter theory from physical theory, as though Newtonian mechanics is silent about metaphysical questions concerning the nature of material bodies. I think there is a different way to understand the shift that took place. Far from being silent, Newtonian mechanics has signifi cant implications for matter theory. With hindsight, we can see that it is not that the traditional questions of matter theory vanish, but rather that the development of Newtonian mechanics enriches the logical and philosophical space in which matter theory is to be explored, profoundly changing the framework within which these issues are to be addressed. In particular, various metaphysical aspects of matter theory-such as whether bodies have actual parts-become entangled with (rather than being independent of, and prior to) the details of the physics. This marks a deep change in the relationship between physics and metaphysics, and one to which any later attempt to do matter theory must pay due attention: the philosophical space changes with the advent of Newtonian theory, and there is no going back.