Philosophy of Science 85.2 (April 2018)
It is commonly claimed that the universality of critical phenomena is explained through particular applications of the renormalisation group. This paper has three aims: to clarify the structure of the explanation of universality; to discuss the physics of such renormalisation group explanations; and to examine the extent to which universality is thus explained.
The derivation of critical exponents proceeds via a real-space or a field-theoretic approach to the renormalisation group. Building on Mainwood (2006), this paper argues that these approaches ought to be distinguished: while the field-theoretic approach explains universality, the real-space approach fails to provide an adequate explanation.
With Eleanor Knox
Studies in the History and Philosophy of Modern Physics 64 (November 2018)
Recent discussions of emergence in physics have focussed on the importance of asymptotic limits. Indeed, some have suggested that emergence is to be analysed entirely in terms of asymptotic limits. We discuss a putative example of emergence that does not fit into this narrative: the case of phonons. These quasi-particles have some claim to be emergent, not least because the way in which they relate to the underlying crystal is almost precisely analogous to the way in which quantum particles relate to the underlying quantum field theory. But there is no need to take a limit when moving from a crystal-lattice based description to the phonon description. Not only does this demonstrate that we can have emergence without limits, but also provides a way of understanding cases that do involve limits.
British Journal for the Philosophy of Science 71.4 (December 2020)
Effective Quantum Field Theories (EFTs) are effective insofar as they apply within a prescribed range of length-scales, but within that range they predict and describe with extremely high accuracy and precision. The effectiveness of EFTs is explained by identifying the features – the scaling behaviour of the parameters – which lead to effectiveness. The explanation relies on distinguishing autonomy with respect to changes in microstates (autonomy_ms), from autonomy with respect to changes in microlaws (autonomy_ml), and relating these, respectively, to renormalisability and naturalness. It is claimed that the effectiveness of EFTs is a consequence of each theory’s autonomy_ms rather than its autonomy_ml.
Philosophy of Science 86.5 (December 2019)
The universality of critical phenomena is best explained by appeal to the Renormalisation Group (RG). Batterman and Morrison, among others, have claimed that this explanation is irreducible. I argue that the RG account is reducible, but that the higher-level explanation ought not to be eliminated. I demonstrate that the key assumption on which the explanation relies – the scale invariance of critical systems – can be explained in lower-level terms; however, we should not replace the RG explanation with a bottom-up account, rather we should acknowledge that the explanation appeals to dependencies which may be traced down to lower levels.
Philosophy 96.1 (January 2021)
Multiple realisation prompts the question: how is it that multiple systems all exhibit the same phenomena despite their different underlying properties? In this paper I develop a framework for addressing that question and argue that multiple realisation can be reductively explained. I illustrate this position by applying the framework to a simple example – the multiple realisation of electrical conductivity. I defend my account by addressing potential objections: contra (e.g.) Polger and Shapiro (2016), Batterman (2018), and Sober (1999), I claim that multiple realisation is commonplace, that it can be reductively explained, but that it requires a sui generis reductive explanatory strategy.
With Vanessa Seifert
British Journal for the Philosophy of Science (Forthcoming)
Whether or not quantum physics can account for molecular structure is a matter of considerable controversy. Three of the problems raised in this regard are the problems of molecular structure. We argue that these problems are just special cases of the measurement problem of quantum mechanics: insofar as the measurement problem is solved, the problems of molecular structure are resolved as well. In addition, we explore one consequence of our argument: that claims about the reduction or emergence of molecular structure cannot be settled independently of the choice of a particular resolution to the measurement problem. Specifically, we consider how three standard putative solutions to the measurement problem inform our understanding of a molecule in isolation, as well as of chemistry’s relation to quantum physics.
EMERGING INTO THE RAINFOREST: EMERGENCE AND SPECIAL SCIENCE ONTOLOGY
With Katie Robertson
Many philosophers of science are ontologically committed to a lush rainforest of special science entities, but are often reticent about the criteria that determine which entities count as real. On the other hand, the metaphysics literature is much more forthcoming about such criteria, but often links ontological commitment to irreducibility. We argue that the irreducibility criteria are in tension with scientific realism: for example, they would exclude viruses, which are plausibly theoretically reducible and yet play a sufficiently important role in scientific accounts of the world that they should be included in our ontology.
In this paper, we show how the inhabitants of the rainforest can be inoculated against the eliminative threat of reduction: by demonstrating that they are emergent. According to our account, emergence involves a screening off condition as well as novelty. We go on to demonstrate that this account of emergence, which is compatible with theoretical reducibility, satisfies common intuitions concerning what should and shouldn't count as real: viruses are emergent, as are trouts and turkeys, but philosophically gerrymandered objects like trout-turkeys do not qualify.
ON THE AUTONOMY OF THE SPECIAL SCIENCES
Draft (available on request)
Fodor (1997) argues that the special sciences are autonomous, but that this autonomy is mysterious and eludes explanation. Reductionist responses to Fodor tend to eliminativism about autonomy. In this paper I set out a framework for explaining autonomy. Rather than eliminating it, this establishes that the special sciences are, in fact, autonomous from more fundamental sciences, but that this is compatible with reductive explanation.
I cash this out with a case study. Nerve signals are autonomous from the individual ionic motions across the neuronal membrane. In order to explain the autonomy of the nerve signal, we ought to identify the structures at the lower level which give rise to the signal's autonomy. In this case we can do just that: the gated ion channels underwrite the autonomy of nerve signals.
HOW TO BE A BOHMIAN REDUCTIONIST
Draft (available on request)
While advocates of Bohmian mechanics generally also endorse local reductionism, it’s far from clear how to make those two positions compatible. The issue is that reductive explanations of the kind ubiquitous in science require reference not just to particle positions but additionally to features only found in the wavefunction. However, the wavefunction is commonly interpreted as a non-local field, law, or universal disposition. As such, reductive explanations of, say, the impermeability of a table essentially refer to entities which are not localised to any subregion of the universe. In order to make sense of such explanations, the Bohmian should engage with the project of articulating an ontology of effectively localised wavefunctions. I suggest ways in which this project may be developed, but note significant technical and conceptual challenges.
MULTISCALE LEVELS AND REDUCTION
Draft (available on request)
Recent literature has raised what I'll call the `multiscale argument' against reduction (see e.g. Batterman (2013), Wilson (2017), Bursten (2018)). These authors observe that numerous successful scientific models appeal to features and properties from a wide range of spatial/temporal scales. This is taken to undermine views that the world is sharply divided into distinct levels, roughly corresponding to different scales, and that each higher level is reducible to the next lowest level.
While the multiscale argument does undermine a naive conception of levels and reduction, in this paper I argue that alternative views of reduction and levels can withstand this argument. After articulating the multiscale argument in more detail, I show that this does not undermine a version of reduction that accepts methodological pluralism in science, yet maintains that the adequacy of any model can be explained by appeal to details at smaller scales. I go on to discuss a case study -- dislocations in steel -- used by Batterman and Wilson in defence of the multiscale argument. I argue that the version of reduction advocated above is available in this context. I conclude by arguing that, in the face of the multiscale argument, levels are either everywhere or nowhere.
SOCIAL CONSTRUCTION, PHYSICAL CONSTRUCTION, AND EMERGENCE
Draft (available on request)
Claims that a kind K is socially constructed play an important role in contemporary political discourse: such claims are taken to establish that K's salience is due to social rather than (e.g.) biological factors. However, some of those who wish to endorse the view that racial kinds' salience is primarily due to social factors argue that the conception of race in mainstream discourse isn't socially constructed (e.g. Hardimon (2017), Garcia (2019)). In this paper, I defend a general account of social construction, and demonstrate that, if applied to the example of racial kinds, it can withstand such critiques.
My account draws a distinction between a kind's having defining properties that are social and a kind's being socially constructed. That distinction allows me to argue that kinds may have non-social defining properties, while still being socially constructed. With this distinction in hand, I draw an analogy between social construction and physical construction, claiming that a person with particular ancestry may be socially constructed as black in just the same way that a liquid with particular underlying properties may be physically constructed as having a particular viscosity.
I then claim that social construction and physical construction are special cases of emergence. I conclude that, first, social construction is less controversial and more generic than is often appreciated, and, second, that the debates over the metaphysics of race should be distinguished from discussions of social construction.