Tim Maudlin has influentially argued that Humeanism about laws of nature stands in conflict with quantum mechanics. Specifically Humeanism implies the principle Separability: the complete physical state of a world is determined by the intrinsic physical state of each space‐time point. Maudlin argues Separability is violated by the entangled states posited by QM. We argue that Maudlin only establishes that a stronger principle, which we call Strong Separability, is in tension with QM. Separability is not in tension with QM. Moreover, while the Humean requires Separability to capture the core tenets of her view, there's no Humean‐specific motivation for accepting Strong Separability. We go on to give a Humean account of entangled states which satisfies Separability. The core idea is that certain quantum states depend upon the Humean mosaic in much the same way as the laws do. In fact, we offer a variant of the Best System account on which the systemization procedure that generates the laws also serves to ground these states. We show how this account works by applying it to the example of Bohmian Mechanics. The 3N‐dimensional configuration space, the world particle in it and the wave function on it are part of the best system of the Humean mosaic, which consists of N particles moving in 3‐dimensional space. We argue that this account is superior to the Humean account of Bohmian Mechanics defended by Loewer and Albert, which takes the 3N‐dimensional space, and its inhabitants, as fundamental.

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.

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.Here is an intuition: Nothing can be mass if it doesn't act like mass. This might seem trivial -of course mass has to act like mass, how could it do anything else? But we can understand the intuition better when we consider certain modal claims: The intuition is that if there is some possible world where some property, P, doesn't act like mass does in our world then P is not mass. If in some other world a property, Q, acts just like the economic property of inflation acts in our world then Q (whether or not it's ever instantiated in our world) is not mass. This implies that in any possible world if there is the property mass then that property must act like mass does in our world. That is to say, it is necessary that the property mass acts in the way it does in our world -it plays the mass-role necessarily. This is an attractive thought. A similarly attractive intuition runs in the other direction: If something acts like mass -for instance, determining the degree to which a body resists changes in its motion -then it is mass. If we know that some property plays the mass-role then we don't need to do any further investigation to find out what it is -it's mass. And if we find a property P and a property Q that both play the mass-role, then P and Q are the same propertymass. Anything that fills the mass-role is necessarily mass.! Thanks to Heather Demarest, Mike Hicks, Vera Matarese and an audience at the University of Birmingham for very helpful feedback. In addition, thanks to all those who helped us with Bhogal and Perry (2017), to which this paper is a follow-up. 1We'll use the term 'Nomic Necessitarianism' to refer to the class of views which capture these intuitions.Specifically, we will count a view as a nomic necessitarian view if it says that (i) a physical property possesses its nomic role -its role in the physical laws (whatever, ontologically, those laws happen to be) -as a matter of metaphysical necessity and (ii) as a matter of metaphysical necessity, no other property possesses that nomic role. That is, a nomic necessitarian view says that, necessarily, P is mass if and only if it plays the mass-role.Nomic necessitarianism is often ac...

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 (pace Dasgupta (2015a)), 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.