Scientific realism is the view that the aim of science is to produce true or approximately true theories about nature. It is a view which not only is shared by many philosophers but also by scientists themselves. Regarding Kuhn’s rejection of scientific progress, Steven Weinberg once declared: “All this is wormwood to scientists like myself, who think the task of science is to bring us closer and closer to objective truth.” But such a realist view on scientific theories is not (...) without problems. The paper discusses some arguments for and against the ontological commitments that scientific theories may entail. The upshot is that scientific realism according to which the semantic content of theories should be understood literally is not sustainable. Instead, it is argued that only realism with respect to entities can be reasonably and practically maintained. Finally, the paper discusses structural realism which presents itself as a modern alternative to scientific realism which may meet both the optimistic no-miracle argument and the pessimistic meta-induction argument. My conclusion is that such a position is neither attractive nor defendable. (shrink)

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The topics of gravitational field energy and energy-momentum conservation in General Relativity theory have been unjustly neglected by philosophers. If the gravitational field in space free of ordinary matter, as represented by the metric g ab itself, can be said to carry genuine energy and momentum, this is a powerful argument for adopting the substantivalist view of spacetime.This paper explores the standard textbook account of gravitational field energy and argues that (a) so-called stress-energy of the gravitational field is well-defined neither (...) locally nor globally; and (b) there is no general principle of energy-momentum conservation to be found in General Relativity. I discuss the nature and justification of the zero-divergence law for ordinary stress-energy, and its possible connection with the failure of General Relativity to realise Mach's principle. (shrink)

Jonathan Lowe argues that metaphysics should be restored to a central position in philosophy, as the most fundamental form of rational inquiry, whose findings underpin those of all other disciplines. He portrays metaphysics as charting the possibilities of existence, by idetifying the categories of being and the relations of ontological dependency between entities of different categories. He proceeds to set out a unified and original metaphysical system: he defends a substance ontology, according to which the existence of the world s (...) one world in time depends upon the existence of persisting things which retain their identity over time and through processes of qualitative change. And he contends that even necessary beings, such as the abstract objects of mathematics, depend ultimately for their existence upon there being a concrete world of enduring substances. Within his system of metaphysics Lowe seeks to answer many of the deepest and most challenging questions in philosophy. (shrink)

In his paper ``What is Structural Realism?'' James Ladyman drew a distinction between epistemological structural realism and metaphysical (or ontic) structural realism. He also drew a suggestive analogy between the perennial debate between substantivalist and relationalist interpretations of spacetime on the one hand, and the debate about whether quantum mechanics treats identical particles as individuals or as `non-individuals' on the other. In both cases, Ladyman's suggestion is that an ontic structural realist interpretation of the physics might be just what is (...) needed to overcome the stalemate. The main thesis of this paper is that, whatever the interpretative difficulties of generally covariant spacetime physics are, they do not support or suggest structural realism. In particular, I hope to show that there is in fact no analogy that supports a similar interpretation of the metaphysics of spacetime points and of quantum particles. (shrink)

We discuss the relationship between the interpretative problems of quantum gravity and those of general relativity. We argue that classical and quantum theories of gravity resuscitate venerable philosophical questions about the nature of space, time, and change; and that the resolution of some of the difficulties facing physicists working on quantum theories of gravity would appear to require philosophical as well as scientific creativity.

Scientific realism is the view that the aim of science is to produce true or approximately true theories about nature. It is a view which not only is shared by many philosophers but also by scientists themselves. Regarding Kuhn’s rejection of scientific progress, Steven Weinberg once declared: “All this is wormwood to scientists like myself, who think the task of science is to bring us closer and closer to objective truth.” But such a realist view on scientific theories is not (...) without problems. The paper discusses some arguments for and against the ontological commitments that scientific theories may entail. The upshot is that scientific realism according to which the semantic content of theories should be understood literally is not sustainable. Instead, it is argued that only realism with respect to entities can be reasonably and practically maintained. Finally, the paper discusses structural realism which presents itself as a modern alternative to scientific realism which may meet both the optimistic no-miracle argument and the pessimistic meta-induction argument. My conclusion is that such a position is neither attractive nor defendable. (shrink)

I reject Norton and Earman's hole argument that spacetime substantivalism is incompatible with determinism. I reconcile these both technically and philosophically. There is a technical definition of determinism that is not violated by pairs of models of the kind used in the hole argument. And technicalities aside, the basic idea of determinism is not violated if we claim that at most one of the two models represents a possible world. This claim can be justified either by metrical essentialism, or by (...) denying transworld identity for points: I prefer the latter. (shrink)

I give an informal outline of the hole argument which shows that spacetime substantivalism leads to an undesirable indeterminism in a broad class of spacetime theories. This form of the argument depends on the selection of differentiable manifolds within a spacetime theory as representing spacetime. I consider the conditions under which the argument can be extended to address versions of spacetime substantivalism which select these differentiable manifolds plus some further structure to represent spacetime. Finally, I respond to the criticisms of (...) Tim Maudlin and Jeremy Butterfield. (shrink)