Why the Parts of Absolute Space are Immobile Nick Huggett

Newton’s arguments for the immobility of the parts of absolute space have been claimed to licence several proposals concerning his metaphysics. This paper clarifies Newton, first distinguishing two distinct arguments. Then, it demonstrates, contrary to Nerlich ([2005]), that Newton does not appeal to the identity of indiscernibles, but rather to a view about de re representation. Additionally, DiSalle ([1994]) claims that one argument shows Newton to be an anti-substantivalist. I agree that its premises imply a denial of a kind of substantivalism, but I show that they are inconsistent with Newton’s core doctrine that not all motion is the relative motions of bodies, and so conclude that they are not part of his considered views on space. 1 The Arguments 2 The Identity Argument 2.1 Identity of indiscernibles for individuals 2.2 Identity of indiscernibles for worlds and states 2.3 Representation de re 3 Kinematic Relationism 4 Conclusion Since Newton took absolute motion to be motion with respect to absolute space, it is not surprising that he held the parts of absolute space to be at mutual rest—otherwise, with respect to what part is absolute motion to be taken? In fact, Newton held the stronger view that the parts were necessarily motionless, and in two well-known passages argued for this claim: first in the unpublished essayDe Gravitatione, and again in the Scholium to theDefinitions in his Principia. The arguments have been rather widely discussed, to various ends, but, I will argue, they have been misunderstood in a number of ways. More specifically, in Section 1, I will argue (against Nerlich [2005], for instance) that De Gravitatione contains two arguments for immobility, while the Scholium contains only one of them. In particular, the ‘identity argument’ that is C ©TheAuthor (2008). Published byOxfordUniversity Press on behalf ofBritish Society for the Philosophy of Science. All rights reserved. doi:10.1093/bjps/axn013 For permissions, please email: [email protected] Advance Access published on July 7, 2008 392 Why the Parts of Absolute Space are Immobile the focus of recent discussion (and this paper) is only found inDe Gravitatione. This point is not made merely to correct a mistake in the literature, but to show that the premises of Newton’s argument do not appear in his more considered, published works, and thus do not have the same status as his core views. Section 2 will canvas some possible interpretations of the identity argument and their problems, and explicate the most charitable, natural reading—according to which the premises are consistent with absolute space as conceived by Newton. One reason that the argument has attracted attention (e.g., DiSalle [1994]) is that it also seems to show that Newton denied a ‘substantival’ view of space: its premises imply rather immediately that worlds that (putatively) differ only in the absolute location of the material universe do not in fact differ at all. Unfortunately for this interpretation of Newton, we shall see in Section 3 that the premises also entail that all motion is the relative motion of bodies. The denial of this doctrine is of course essential to Newton’s natural philosophy. Since the problematic argument appears only in his unpublished writings, it thus seems best to bracket it from his considered views—as a result, the identity argument is, after all, no evidence that Newton seriously or consciously denied substantivalism.