Kent A. Peacock

The purpose of this paper is to pick up the threads of a debate about the ontology of becoming in spacetime that was triggered by a provocative article published by Nicholas Maxwell in 1985. This debate is itself merely a recent episode in a long dialogue that goes back at least as far as the time of Parmenides and Heraclitus. Here is the question around which this debate centres: is change or becoming the distinguishing feature of the natural or physical world, as suggested obscurely by Heraclitus and argued at length by Aristotle? Or is our usual uncritical belief in the reality of change the product of some sort of perceptual illusion or intellectual error, as believed by Parmenides and a small host of recent authors such as Gödel and Julian Barbour? I won’t be able to solve the whole of this momentous problem here. However, I intend both to set aside a few unwarranted assumptions which have for a long time dogged our thinking about the puzzle of becoming, and to assemble some tools which should aid in finding a solution to it. In particular, I will argue that we can do much better than is usually supposed in identifying structures which can both “live” within Minkowski spacetime and represent objective becoming. I shall also discuss whether such structures would necessarily contradict the Principle.

I present a thought experiment in quantum mechanics and tease out some of its implications for the doctrine of “peaceful coexistence”, which, following Shimony, I take to be the proposition that quantum mechanics does not force us to revise or abandon the relativistic picture of causality. I criticize the standard arguments in favour of peaceful coexistence on the grounds that they are question-begging, and suggest that the breakdown of Lorentz-invariant relativity as a principle theory would be a natural development, given the general trend of physics in this century.

It is generally believed that an invariant notion of a global present or "Now" cannot be defined in special relativity, because of the relativity of optical simultaneity. I argue that this may be a non sequitur since it is not necessarily the case that the psychological "Now" should be thought of as associated with constant time slices in spacetime. By considering a science fictional version of the Twin Paradox due to Robert A. Heinlein, I argue that it is psychologically plausible to associate the common specious present of several observers in relative motion with certain hypersurfaces of proper time of those observers corrected for acceleration history and relative motion in an obvious way. If this is correct then the relativity of optical simultaneity may be simply irrelevant to the question of the relativity of a globally distinguished "present".

Naturalism in Mathematics PENELOPE MADDY, 1997 Oxford, Oxford University Press viii + 254 pp., $CAN91, ISBN 0–19–823573–9 Bohmian Mechanics and Quantum Theory: an Appraisal JAMES T. CUSHING, ARTHUR FINE & SHELDON GOLDSTEIN, 1996 Dordrecht, Kluwer viii + 403, pp., US$159.00, ISBN 0–7923–4028–0 Pragmatism as a Principle and Method of Right Thinking: the 1903 Harvard Lectures on Pragmatism CHARLES SANDERS PEIRCE, 1997 Edited and introduced, with a commentary, by PATRICIA ANN TURRISI Albany, State University of New York Press xi + 305 pp., $26.53 ISBN 0–7914–3265–3 ISBN 0–7914–3266–1