Duality, Fundamentality, and Emergence

Dualities offer new possibilities for relating fundamentality and emergence. In particular, as this chapter aims to show, it may happen that the relations of fundamentality and emergence between dual theories are inverted. In other words, the direction of emergence typically found in these cases is opposite to the direction of emergence followed in the standard accounts: that is, while the standard emergence direction is that of decreasing fundamentality—in that there is emergence of less fundamental, high-level entities, out of more fundamental, low-level entities—in these cases of duality, on the contrary, a more fundamental entity can emerge out of a less fundamental one. In fact, this possibility can be traced back to the existence of different classical limits in quantum field theories and string theories.

In Defense of the Metaphysics of Entanglement

Quantum entanglement has long been thought to have deep metaphysical consequences. For example, it has been claimed to show that Humeansupervenience is false or to involve a novel form of ontological holism. One way to avoid confronting the metaphysical consequences is to adopt some form of antirealism. This chapter discusses two prominent strands in recent literature—wavefunction realism and “Super-Humeanism”—which appear quite different but, as the authors see it, are instances of a more general strategy. In effect, what these attempt to do is to diffuse the puzzle of entanglement by eliminating it. These interpretative movements are advertised as equally realist, but, the chapter claims, fail to take an appropriately realist attitude towards entanglement. What the chapter advocates instead is a genuine metaphysics of entanglement: instead of eliminating entanglement, develop a metaphysics that accounts for and explains it.

Classifying Dependencies

Do causes always precede their effects? Is causation across a temporal gap possible? Is simultaneous causation possible? The comparative neglect of such questions means that we still lack a clear view of the underlying nature of causation. Metaphysicians typically distinguish sharply between grounding and causation, and philosophers of science typically distinguish sharply between causal and non-causal explanation, but there has been surprisingly little discussion of how exactly to draw these distinctions. This chapter argues that six of the most obvious criteria fail to capture the intended distinction between causation and grounding. The chapter proposes and defends an alternative criterion in terms of the principles mediating the dependency, and explores some of the implications of this criterion for the possibility of simultaneous causation in physics.

Radical Structural Essentialism for the Spacetime Substantivalist

Spacetime substantivalists insist that spatiotemporal points are fundamental entities and thus are ontologically independent from the physical objects occupying these points.This chapter argues that the best metaphysical option for the substantivalist is to adopt a radical version of structural essentialism, according to which participation in a certain relational structure is both a necessary and sufficient condition of identity for the elements characterized by this structure.It comparesthe author’sproposed variant of essentialism with some alternative conceptions, such as Tim Maudlin’s metric essentialism and David Glick’s Minimal Structural Essentialism. It discusses how the author’sRadical Structural Essentialism deals with the challenge of the hole argument as well as some less well-known challenges, such as the problem of contingent counterfactuals regarding the material contents of spacetime, and the ‘mole’ argument. Later the chapter explains why the structure consisting of the metric tensor is a genuinely relational structure, and itdefend the claim that in order to preserve the identity of its elements the actual structure may be merely embeddable in (and not necessarily isomorphic with) an alternative structure.

On the Independent Emergence of Space-time

Physics might show that space-time is an emergent structure without describing its ontological basis. Space and time are fundamental to metaphysics and physics. Their union remained fundamental after special relativity doomed each separately to fade away as a mere shadow of the space-time that Einstein later took to exist only as a structural quality of the gravitational field of general relativity. But problems meshing general relativity with quantum theory appear to show that space-time structure is not fundamental but emerges within a quantum theory of gravity. In a pragmatist view, quantum theory is typically applied not to represent target systems but to guide rational credence about events involving other systems. Applied to a gravitational field, quantum theory may guide credence about events in an emergent space-time without itself representing that field. If so, a fundamental physical theory would not describe any ultimate ground of space-time and its contents.

Wave Function Realism in a Relativistic Setting

The purpose of the present chapter is to respond to a thread of recent criticism against one candidate framework for interpreting quantum theories, a framework introduced and defended by David Albert and Barry Loewer: wave function realism, a framework for interpreting the ontology of quantum theories according to which what appears to be a nonseparable metaphysics ofentangled objects acting instantaneously across spatial distances is a manifestation of a more fundamental separable and local metaphysics in higher dimensions. Thechapterconsiders strategies for extending the wave function realist interpretation of quantum mechanics to the case of relativistic quantum theories, responding to arguments that this cannot be done.

What Entanglement Might Be Telling Us: Space, Quantum Mechanics, and Bohm’s Fish Tank

There are pressures that are coming from a number of quarters in quantum cosmology to view space or space-time as an emergent structure. But in recent years in the foundations of standard, non-relativistic quantum mechanics, interpretations have emerged that treat space as emergent. My primary purpose is (i) to make explicit the considerations stemming from quantum mechanics alone, that are pushing in the direction of viewing space (or space-time) as an emergent structure, and (ii)to clarify exactly what it means to say that space is emergent in the sense that this chapter is interested inhere. Itdoes that by presenting some simple low-dimensional models that reproduce central features of quantum phenomena, and analyzing the examples with attention to the difference between two different kinds of explanation: one in which the correlations emerge from a more fundamental (and not ultimately spatial) description and one in which correlations are explained by influences that pass through the space in which the correlated events are situated.

Introduction

In recent years, fundamentality and emergence have come to occupy a central place in both metaphysics and the philosophy of physics. Many metaphysicians now think that, in giving a complete account of reality, saying what exists is only part of the story—we also need to say how everything “hangs together.” Meanwhile, philosophers of physics have begun to appreciate that much of physics—including current so-called “fundamental physics”—in fact concerns effective or emergent levels. A point of intersection between these two areas is the status of spacetime. Is it possible that spacetime itself is non-fundamental? What would this mean for our understanding of reality?...

Fundamental and Derived Quantities

A widespread view in metaphysics holds that some properties, perfectly natural ones, have an elite status among properties. As part of a naturalistic approach to metaphysics, it is commonly presumed that science—in particular physics—will reveal which properties in fact play the role of these elite properties. Since properties in physics are often quantitative, this raises the question whether all quantities are elite properties, or whether there is a distinction between fundamental and non-fundamental quantities, with only the former being candidates for elite properties. In this chapter I investigate whether the distinction between base quantities and derived quantities found in systems of units can serve as a basis for distinguishing between fundamental and non-fundamental quantities. My conclusion is aporetic: it seems clear that not all quantities are equally fundamental, yet a general criterion for fundamentality (or non-fundamentality) based on physics alone remains elusive.

Fundamentality and Non-Symmetric Relations

The first part of this chapter argues that there are no non-symmetric relations at the fundamental level. The second part identifies different ways in which asymmetry and order can be introduced into a world that only contains symmetric but no non-symmetric fundamental relations. The third part develops an account of derivative relations and puts forward identity criteria that establish that derivative non-symmetric relations do not have distinct converses. Instead of a plurality of relations, there are only different ways of picking out the same relation. The final part provides an account of how generative operations can induce order and argues for a reconceptualisation of grounding as an operation rather than as a relation.