Physics and scientific realism

Abstract

In this thesis I argue for a realist interpretation of physics. I respond to claims to the contrary by submitting rebuttals of some of the more serious objections, and by formulating and defending counter-claims. It would be too ambitious to try to argue here for realism throughout physics, so I restrict my constructive efforts to the classical domain. Attempted rebuttals of the anti-realist case, however, involve intrusions into the quantum arena. I take issue in Part 1 with Nancy Cartwright. She argues in How the Laws o f Physics Lie that: (i) the fundamental laws of physics are false; (ii) causal explanation can ensure truth, in which case the theoretical entities invoked are real; and (iii) current theories of explanation are misconceived. To support (i) she analyses cases drawn from both classical and modern physics, and my response is to show in detail how, in these examples, I believe she is mistaken. Whilst I agree with (ii), I argue that there is incoherence in simultaneously holding (ii) with (i). As for (iii), I defend the D-N model of explanation and point to the inadequacies of Cartwright s simulacrum model. In Representing and Intervening Ian Hacking argues for the reality of (theoretical) entities that can be manipulated in interactions with other things. However, he is agnostic on realism about theories, because he believes that incompatible theories can equally well cover a given range of phenomena. The case to which he points to instantiate the view is Hertz s treatment of mechanics in which Hacking claims to find three equally good theories, with the overt threat of inconsistency among them. In Part 2 I argue that there is but one theory of mechanics and that Hertz s project was to investigate three different ways of axiomatising it. Only one of the three ways (as conceived by Hertz) survives. To support their position, anti-realists commonly seize on the doctrine, supposedly due to Pierre Duhem, that a given range of phenomena can be accommodated by different, mutually incompatible, theories. Part 3 examines the basis for Duhem's view and establishes that he had a quasi-realist attitude to theories. The originator of the doctrine, it transpires, was not Duhem, but Henri Poincare. I explain how the subsequent course of physics invalidated the grounds which misled these two philosophers into adopting it. Part 4 examines Bas van Fraassen's claim to reduce to absurdity the demand for explanation that he thinks is exemplified in J.J.C. Smart's classic cosmic coincidence' argument for realism. I show that Smart s argument comprehends two different sorts of cosmic coincidence, and that van Fraassen addresses only the less formidable of these. In so doing, van Fraassen's strategy is to assert that Smart's argument relies on Reichenbach s principle of the common cause, and to offer an abstract schema (deriving from the EPR correlation experiments) which, he claims, refutes Reichenbach's principle. I set all of this in context and argue that the schema fails to bear the load that van Fraassen places on it, and that Smart s argument stands.