Elizabeth Miller

For Humean atomists, cosmic contents supervene on a spatiotemporal mosaic of modally insulated, freely recombinable local qualities. One piecemeal subspecies of Humean atomism promises more than global supervenience—somehow or other—on a separable base; it constrains how exactly elemental inputs yield everything else. Roughly, the distribution of basic local qualities across elements in one part of our cosmos metaphysically suffices for the complete local physical state of that part: anything sharing this part’s basic elemental decoration should share its more complete contents, regardless of what may be happening elsewhere. On a non-piecemeal alternative, derivative contents can be recognizably local to, or manifest within, one part of our cosmos while reflecting some more global elemental base. To develop this alternative, non-piecemeal Humeans can borrow inspiration from some critics of Humean supervenience, who already distinguish a broader notion of locality from strict Humean intrinsicality.

I argue that Schaffer fails to provide a non-question-begging argument for priority monism. Despite his suggestion to the contrary, Humean pluralists need not, and plausibly do not, endorse his tiling constraint on metaphysically basic objects. Moreover, the distinction between supervenience—of the sort at issue in Humean doctrine—and metaphysical necessitation—of the sort at issue in Schaffer’s tiling constraint—points toward an alternative treatment of the phenomena initially inspiring Schafferian monism. There is an important possibility, one that Humeans can or should embrace, that Schaffer overlooks when drawing his monistic conclusion.

For Humeans, many facts—even ones intuitively “about” particular, localized macroscopic parts of the world—turn out to depend on surprisingly global fundamental bases. We investigate some counterintuitive consequences of this picture. Many counterfactuals whose antecedents describe intuitively localized, non-actual states of affairs nevertheless end up involving wide-ranging implications for the global, embedding Humean mosaic. The case of self-undermining chances is a familiar example of this. We examine that example in detail and argue that popular existing strategies such as “holding the laws fixed as laws” or “holding the laws fixed as true” are of no help. Interestingly, we show how a new proposal that draws on the resources of the Mentaculus can yield the right results—but only on the assumption that the Humean can make cross-world identifications. We go on to argue that the Humean cannot make such identifications. We conclude that the root of this trouble is deeper, and its reach broader, than the familiar cases suggest. We think it is very much an open question whether the Humean has sufficient resources to properly conceptualize macroscopic objects or to analyze these “local” counterfactuals.

A simple argument proposes a direct link between realism about quantum mechanics and one kind of metaphysical holism: if elementary quantum theory is at least approximately true, then there are entangled systems with intrinsic whole states for which the intrinsic properties and spatiotemporal arrangements of salient subsystem parts do not suffice. Initially, the proposal is compelling: we can find variations on such reasoning throughout influential discussions of entanglement. Upon further consideration, though, this simple argument proves a bit too simple. To get such metaphysically robust consequences out, we need to put more than minimal realism in. This paper offers a diagnosis: our simple argument seems so compelling thanks to an equivocation. The predictions of textbook quantum theory already resonate with familiar holistic slogans; for realists, then, any underlying reality, conforming to such predictions, also counts as holistic in some sense or other, if only by association. Such associated holism, though, does not establish the sort of specific, robust supervenience failure claimed by our simple argument. While it may be natural to slide to this stronger conclusion, facilitating the slide is not minimal realism per se but an additional explanatory assumption about how and why reality behaves in accordance with our theory: roughly, quantum theory accurately captures patterns in the features and behaviors of physical reality because some underlying metaphysical structure constrains reality to exhibit these patterns. Along with the diagnosis comes a recommendation: we can and should understand one traditional disagreement about the metaphysics of entanglement as another manifestation of a familiar and more general conflict between reductive and non-reductive conceptions of metaphysical theorizing. Such reframing makes clearer what resources reductionists have for resisting the simple argument’s challenge from quantum holism. It also has an important moral for their opponents. Traditional focus on whole-part supervenience failure distracts from a root disagreement about metaphysical structure and its role in our theorizing. Non-reductionists fond of our simple argument would be better off tackling this root directly.

The GRW dynamics propose a novel, relevantly “observer”-independent replacement for orthodox “measurement”-induced collapse. Yet the tails problem shows that this dynamical innovation is not enough: a principled alternative to the orthodox account demands some corresponding ontological advancement as well. In fact, there are three rival fundamental ontologies on offer for the GRW dynamics. Debate about the relative merits of these candidates is a microcosm of broader disagreement about the role of ontology in our physical theorizing. According to imprimitivists, the GRW dynamics directly describe (only) some (element’s) undulation in an unfamiliar high-dimensional physical field. Primitivists resist this GRW0 proposal on the grounds that it fails to secure comprehensible contact with our data about macroscopic objects in ordinary lowdimensional space-time. They expect an adequate fundamental ontology to include at least some spatiotemporally localized entities—intuitively, concrete constituents of our familiar macroscopic landscape. The most compelling case goes by way of distributional basing: minimally, primitivists expect a theory’s predictions immediately about spatiotemporal distributions of fundamental entities to provide a supervenience base for data about configurations of macroscopic objects. But while the background intuition is familiar, the distributional model is surprisingly subtle. Lack of clarity about its details generates serious confusion for both sides of our debate.

Quantum mechanics allegedly supports a holistic metaphysical moral: it is not the case that the intrinsic characters of all entangled wholes supervene on intrinsic properties and spatiotemporal arrangements of proper parts. According to one influential line of reasoning, such holistic supervenience failure follows more or less directly from quantum theory itself. One advertised consequence is the defeat of a natural, broadly reductive worldview commonly linked to Lewis's philosophical doctrine of Humean supervenience. However, the situation is more complicated, in both this and other respects, than it may first appear. This article is an opinionated overview of some especially interesting complications.

David Lewis is a natural target for those who believe that findings in quantum physics threaten the tenability of traditional metaphysical reductionism. Such philosophers point to allegedly holistic entities they take both to be the subjects of some claims of quantum mechanics and to be incompatible with Lewisian metaphysics. According to one popular argument, the non-separability argument from quantum entanglement, any realist interpretation of quantum theory is straightforwardly inconsistent with the reductive conviction that the complete physical state of the world supervenes on the intrinsic properties of and spatio-temporal relations between its point-sized constituents. Here I defend Lewis's metaphysical doctrine, and traditional reductionism more generally, against this alleged threat from quantum holism. After presenting the non-separability argument from entanglement, I show that Bohmian mechanics, an interpretation of quantum mechanics explicitly recognized as a realist one by proponents of the non-separability argument, plausibly rejects a key premise of that argument. Another holistic worry for Humeanism persists, however, the trouble being the apparently holistic character of the Bohmian pilot wave. I present a Humean strategy for addressing the holistic threat from the pilot wave by drawing on resources from the Humean best system account of laws

In a recent paper, Barry Loewer attempts to defend Humeanism about laws of nature from a charge that Humean laws are not adequately explanatory. Central to his defense is a distinction between metaphysical and scientific explanations: even if Humeans cannot offer further metaphysical explanations of particular features of their “mosaic,” that does not preclude them from offering scientific explanations of these features. According to Marc Lange, however, Loewer’s distinction is of no avail. Defending a transitivity principle linking scientific explanantia to their metaphysical grounds, Lange argues that a charge of explanatory inadequacy resurfaces once this intuitive principle is in place. This paper surveys, on behalf of the Humean, three strategies for responding to Lange’s criticism. The ready availability of these strategies suggests that Lange’s argument may not bolster anti-Humean convictions, since the argument rests on premises that those not antecedently sharing these convictions may well reject. The three strategies also correspond to three interesting ways of thinking about relations of grounding linking Humean laws and their instances, all of which are consistent with theses of Humean supervenience, and some of which have been heretofore overlooked.