Friday, September 25, 2009

The Shadows of Totalization, Part XXXIX

“The text [ Newton's De Gravitatione, unpublished until 1962] is largely focused on presenting an extended series of criticisms of Cartesian natural philosophy; and, it is significant for understanding Newton's thought, not least because it represents his most sustained known philosophical discussion.

Three aspects of De Gravitatione merit discussion here. The first two involve Newton's rejection of Cartesian views of space, time and motion, and the third centers on his rejection of a broadly Cartesian conception of body. To begin with the first point: in much of De Gravitatione, Newton is apparently concerned to emphasize a series of problems with Descartes's basic conception of space, time, and motion; some of these problems, in turn, stem from the fact — at least from Newton's point of view — that Descartes presents conceptions of space, time and motion that fail to reflect a proper understanding of the basic principles of physics. This is a particularly pressing matter, of course, since Descartes should be credited with one of the very first modern formulations of the principle of inertia, which was obviously central to the later development of Newtonian mechanics. Since the Stanford Encyclopedia includes an extensive entry on Newton's view of space, time and motion, suffice it to say here that Newton takes Descartes's relationalism to fail to account for the proper distinction between true and merely apparent motion. One of the primary goals of Newton's Principia is to make this distinction rigorous and clear.

This point about Descartes's relationalism might be considered an internal criticism of Descartes's system for two reasons. Descartes himself attempts to distinguish between true — or “proper” [proprie/propre] — motion and motion in a “vulgar” or “ordinary” sense [vulgarem/commun], and does so in what we might call a relationalist fashion. For Descartes, whereas motion in the vulgar sense is “the action by which a body travels from one place to another,” motion in the proper sense is “the transfer of one piece of matter, or one body, from the vicinity of the other bodies which immediately touch it, and which we consider to be at rest, to the vicinity of other bodies” (Principles of Philosophy, Part Two, sections 24-25| Descartes 1644/1982, 53-4). Indeed, in the Scholium to the Principia, it seems that Descartes's “proper” motion, defined in terms of the relations of bodies contiguous to a given body, becomes Newton's relative motion. That is, Newton remarkably refashions Descartes's own distinction between the “ordinary” and the “proper” definitions of motion by contending that the latter is sufficiently precise for ordinary affairs, but not for physics. The second reason is this: Newton takes the fashioning of the distinction between true and merely apparent motion to be one of the primary goals not just of his physics, but also of Cartesian physics. So in De Gravitatione, Newton seems to conclude that Cartesian physics fails on its own terms. (Whether this is a fair assessment, of course, is a separate issue.)”

Janiak, Andrew, "Newton's Philosophy" The Stanford Encyclopedia of Philosophy (Fall 2008 Edition), Edward N. Zalta (ed.)


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