This article motivates and develops a reductive account of the structure of certain physical quantities in terms of their mereology. That is, I argue that quantitative relations like "longer than" or "3.6-times the volume of" can be analyzed in terms of necessary constraints those quantities put on the mereological structure of their instances. The resulting account, I argue, is able to capture the intuition that these quantitative relations are intrinsic to the physical systems they’re called upon to describe and explain.

Humeanism – the idea that there are no necessary connections between distinct existences – and Nomic Essentialism – the idea that properties essentially play the nomic roles that they do – are two of the most important and influential positions in the metaphysics of science. Traditionally, it has been thought that these positions were incompatible competitors. We disagree. We argue that there is an attractive version of Humeanism that captures the idea that, for example, mass essentially plays the role that (...) it actually does in the laws of nature. In this paper we consider the arguments that have lead many to conclude that Humeanism cannot be combined with Nomic Essentialism; we identify the weaknesses in these arguments; and we argue in detail that a version of Humeanism based on a variant of the Best System account of laws captures the key intuitions behind nomic essentialism. (shrink)

This article introduces and motivates the notion of a “properly extensive” quantity by means of a puzzle about the reliability of certain canonical length measurements. An account of these measurements’ success, I argue, requires a modally robust connection between quantitative structure and mereology that is not mediated by the dynamics and is stronger than the constraints imposed by “mere additivity.” I outline what it means to say that length is not just extensive but properly so and then briefly sketch an (...) application of proper extensiveness to the project of providing a reductive ground for metric quantitative structure. (shrink)

According to substantivalism, spacetime points and regions are real entities whose existence is not dependent on matter. In this paper, I motivate and defend a version of substantivalism which takes the totality of spacetime as fundamental, and show how this position avoids certain problem cases, in particular the objection from static Leibniz shifts, and better conforms to how we think about space in physics. I argue that, even though the static Leibniz shifts do not show ordinary substantivalism is committed to (...) in-principle undetectable physical structure ), they do indicate something problematic about the modal profile of space-time and its constituents. While the problem is modal, the solution cannot be solely a matter of revising the substantivalist's modal claims. Rather, I argue, the substantivalist must revise her background ontology of space-time. I show how this can be done by developing substantivalist theory that rejects this picture in favor of an alternative ontology of space-time in the spirit of priority monism. (shrink)

I present an argument against the view that the additivity of mass (i.e., the property according to which a composite object’s mass is the “sum” of its parts’) is metaphysically independent of dynamical laws governing massive bodies. In particular, taking additivity to be independent of dynamics commits you to widespread unexplained correlations between the mass properties of composites and the dynamic behavior of massive bodies. The second half of the paper extends this explanatory worry, showing that the very same considerations (...) apply to aspects of mass’s quantitative structure. This gives rise to a new and powerful objection to certain influential theories about the fundamental structure of physical quantities —most notably the magnitude realism of Peacocke (2019) and the second-order absolutist accounts defended by Mundy (1987) and Eddon (2013b). (shrink)