- One way to present a philosophical problem about the identity through time of physical objects is initially to conceive of an object (or, strictly, an object's history) as comprised of a temporal succession of momentary stages. Evidently not just any succession of object-stages corresponds to a single persisting object; some do and some do not. The early stages of one object do not ordinarily go together with the later stages of a second to add up to the history of some single third object. So in order for object-stages to add up to a single persisting object they must be related in some special way. What we want is an analysis or definition of what that relationship is.
- In a sense, of course, any succession of object-stages, however arbitrary, does add up to something: perhaps to an event, or to a state-of-affairs or, if nothing else, at least to a "merely arbitrary succession of object-stages." What is important, however, is that not every succession adds up to a persisting object or body (I use these here interchangeably), where this fundamental category is to be under stood as loosely comprising items which can straightforwardly be said to occupy space and to persist through time. Clearly only certain privileged successions are accorded the special status of uniting into a single persisting object in this sense, which gives rise to the question as to what the unity-making relationship is in virtue of which some successions enjoy this special status.
- One can usefully distinguish three kinds of responses to this question. The first is in a way an anti-response, and is associated with one traditional notion of substance. According to this view the unity-making relationship which constitutes the persistence of material substance cannot be analyzed or explained in terms of any ordinary observable properties or relations. This mode of persistence is consequently regarded as in some sense ultimate. I shall present an interpretation of this view in section V of this paper when I discuss the identity of matter.
- A second response is to maintain that we can formulate a general analysis of the unity-making relationship in terms of such notions as qualitative and spatiotemporal continuity. This approach is fairly prevalent in empiricist literature on the subject and a version of it which is found in Russell and Broad will be discussed in section III.
- Finally there is the sortal theory which Wiggins and others have lately espoused and which I shall initially examine. The basic idea here is that the only way to give a proper analysis of our concept of identity through time is first to divide objects into different sorts (where different sorts are roughly associated with different nouns). We cannot, as in the Russell-Broad approach, provide one general analysis which would be applicable to the unity-making relationship of every different sort of object (we cannot state "identity criteria" for objects in general), but what we can do is provide, with respect to each differentiated sort of object, an analysis of the distinctive unity-making relationship which applies to that sort.
- On the whole I intend to argue for a position which is something of a compromise between the three just mentioned. …
Footnote 1: Truncated somewhat arbitrarily.
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