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 (Forthcoming)
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.
CAN MULTIPLE REALISATION BE EXPLAINED?
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, on this framework, multiple realisation can be reductively explained. I defend this position by applying the framework to a simple example – the multiple realisation of electrical conductors. I go on to compare my position to views advocated in Polger & Shapiro (2016), Batterman (2018), and Sober (1999). Contra these respective authors I claim that multiple realisation is commonplace, that it can be explained, but that it requires a sui generis reductive explanatory strategy. As such multiple realisation poses a non-trivial challenge to reduction, which can, nonetheless, be met.
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.