Robert DiSalle

Spacetime theory as physical geometry

Discussions of the metaphysical status of spacetime assume that a spacetime theory offers a causal explanation of phenomena of relative motion, and that the fundamental philosophical question is whether the inference to that explanation is warranted. I argue that those assumptions are mistaken, because they ignore the essential character of spacetime theory as a kind of physical geometry. As such, a spacetime theory does notcausally explain phenomena of motion, but uses them to construct physicaldefinitions of basic geometrical structures by coordinating them with dynamical laws. I suggest that this view of spacetime theories leads to a clearer view of the philosophical foundations of general relativity and its place in the historical evolution of spacetime theory. I also argue that this view provides a much clearer and more defensible account of what is entailed by realism concerning spacetime.

Conventionalism and Modern Physics: A Re-Assessment

Conventionalism implied that physical geometry must be fixed by an arbitrary choice among equivalent alternatives. In the last half-century, this view has retreated before arguments that allegedly equivalent geometries are not at all equivalent on decisive empirical and methodological grounds. Yet such arguments were familiar to, and even proposed by, the conventionalists themselves. Poincare, Schlick, and Reichenbach—to take just three prominent examples—aimed not to deny that one could rationally choose among physically possible alternative geometries, but to articulate an epistemological theory of the origins of geometrical postulates. According to this theory, the empirical application of geometry depends on principles that are not themselves empirical, principles which were characterized as stipulations. But this view certainly allowed that some stipulations were better than others for the analysis of natural phenomena. Thus Reichenbach, Schlick, and Carnap could maintain that Einstein’s general theory of relativity had revealed the arbitrary element in physical geometry, while at the same time demonstrating the superiority of non-Euclidean geometry. A more recent challenge to conventionalism is that the very idea of a geometrical stipulation does not even make sense in the context of general relativity, which relates geometrical structure to the distribution of matter. On Friedman’s view, conventionalism presupposes the nineteenth-century view of geometry as a fixed and uniform background against which the laws of physics are framed. But according to general relativity, physical geometry varies with material circumstances, and so cannot be settled in advance by convention. Thus geometry can no longer be interpreted as part of an a priori background for physics, settled by an initial choice of a theoretical language. Friedman’s assessment brings out two conflicting aims behind the conventionNOUS 36:2 ~2002! 169–200

Conventionalism and the Origins of the Inertial Frame Concept

This paper examines methodological issues that arose in the course of the development of the inertial frame concept in classical mechanics. In particular it examines the origins and motivations of the view that the equivalence of inertial frames leads to a kind of conventionalism. It begins by comparing the independent versions of the idea found in J. Thomson (1884) and L. Lange (1885); it then compares Langes conventionalist claims with traditional geometrical conventionalism. It concludes by examining some implications for contemporary philosophy of space and time.

Einstein, Newton and the empirical foundations of space time geometry

Abstract Einstein intended the general theory of relativity to be a generalization of the relativity of motion and, therefore, a radical departure from previous spacetime theories. It has since become clear, however, that this intention was not fulfilled. I try to explain Einsteins misunderstanding on this point as a misunderstanding of the role that spacetime plays in physics. According to Einstein, earlier spacetime theories introduced spacetime as the unobservable cause of observable relative motions and, in particular, as the cause of inertial effects of ‘absolute’ motion. I use a comparative analysis of Einstein and Newton to show that spacetime is not introduced as an explanation of observable effects, but rather is defined through those effects in arguments like Newtons ‘water bucket’ argument and Einsteins argument for special relativity. I then argue that to claim that a spacetime theory is true, or to claim that a spacetime structure is ‘real’, is not to claim that a theoretical object explai...

Analysis and Interpretation in the Philosophy of Modern Physics

William Demopoulos identified a particular kind of “conceptual analysis” as a central achievement of the analytic tradition in philosophy, with far-reaching implications for the philosophy of mathematics and the mathematical sciences. I present an overview of this notion of conceptual analysis, the part that it has played in the construction and interpretation of physical theory, and its implications for some general questions about the relation between formal theories and experience.

Poincaré on the Construction of Space-Time

One of the enduring challenges for the interpreter of Poincare is to understand the connections between his analysis of the geometry of space and his view of the development of the theory of space-time. On the one hand, he saw that the invariance group of electrodynamics determines a four-dimensional space with a peculiar metrical structure. On the other hand, he resisted Einstein’s special theory of relativity, and continued to regard the Newtonian space-time structure as a sufficient foundation for the laws of physics. I propose to approach this question by considering the privileged position that space plays, according to Poincare, in our conception of the physical world, and particularly in the construction of the fundamental concepts by which physical processes submit to objective measurement. Poincare’s position results from granting the concept of space an epistemological priority that, in the face of modern physics, it was unable to sustain.

Analysis and Interpretation in the Exact Sciences

Of course, from childhood to forever, we are always thought to love reading. It is not only reading the lesson book but also reading everything good is the choice of getting new inspirations. Religion, sciences, politics, social, literature, and fictions will enrich you for not only one aspect. Having more aspects to know and understand will lead you become someone more precious. Yea, becoming precious can be situated with the presentation of how your knowledge much.

Pitholes in Space-Time: Structure and Ontology of Physical Geometry

The philosophy of space and time did not begin with Newton and Leibniz, but there are perfectly good reasons why contemporary discussions see their origin in the controversy between those two. On the one hand, the issues explicitly raised between them—especially, and most obviously, the epistemological and methodological questions surrounding Newton’s theory of absolute space and motion—have never lost their relevance to the continuing evolution of physics. On the other hand, in different but equally unprecedented ways, they saw the question of the nature of space and time as part of a larger set of deeply interconnected questions, not only in the foundations of physics, but also in metaphysics, epistemology, and the foundations of mathematics.