El abastecimiento en la retaguardia rondeña

Having, I hope, exhausted for the time being the dubious attractions of the property instantiation approach, let us turn next to the temporal parts approach. (Later on I shall develop a further argument inimical to both of these approaches.) This second approach differs from the first chiefly only

151 The point may be highlighted by the familiar examples of cases in which, very plausibly, we should say that two distinct material objects exist in precisely the same place at the same time—for instance, a bronze statue and the lump of bronze of which it is made. What I would emphasize is that such spatiotemporal coincidence is possible precisely because statues and lumps of bronze have different criteria of identity —for this confirms that the direction of explanation runs from criteria of identity to exclusion (or non-exclusion) principles, rather than vice versa.

in replacing talk of the (full and singular) instantiation of tomatohood at a certain place and time by talk of the existence at a place and time of a temporal part, or stage, or slice of a tomato. A diachronic identity criterion for tomatoes will then be framed in terms of spatiotemporal-cum-causal conditions on sets or sequences of such temporal parts.

This approach has an apparent advantage over the previous one in that the temporal parts of tomatoes, whatever exactly they may be, plainly cannot just be the same sorts of things as tomatoes themselves—and hence there is no immediate threat of circularity to attempts to frame a diachronic identity criterion for tomatoes in terms which invoke such entities.¹⁵² Whereas talk of the (full and singular) instantiation of tomatohood at a certain place and time was transparently just an oblique way of speaking of the existence at that place and time of exactly one whole tomato, talk of the existence at a certain place and time of a temporal part or stage of a tomato is not so obviously a merely verbal ploy.

But in a less direct way the temporal parts approach does indeed appear to be viciously circular. For how are the

‘temporal parts’ of tomatoes (assuming indeed that we countenance the existence of such entities at all) to be individuated and identified save by reference to the very tomatoes of which they are parts? The expression ‘temporal part of a tomato’ is a theoretical term of art, unlike the term ‘tomato’ itself, so that it is not open to one just to leave the question of their individuation to ‘common sense’ or ‘intuition’.¹⁵³It will be helpful at this point to compare the notion of a temporal part of a tomato with that of one of its spatial parts, which is a good deal more familiar (remembering here that it was in terms of just such a comparison that we eventually settled upon an interpretation of the term ‘temporal part’ for the purposes of Chapter 4). Now, the phrase

152 Some philosophers do, I concede, believe that a temporal part of an object of the sort F may (particularly if the part has quite an extended duration) itself qualify as an object of the sort F : see e.g. Anthony Quinton, The Nature of Things (London: Routledge & Kegan Paul, 1973), 70. But I can see no advantage for them in this, and only the disadvantage of having to face the threat of immediate circularity which may otherwise be avoided.

153 In his second postscript to ‘Survival and Identity’, David Lewis writes: ‘A person-stage is a physical object, just as a person is . . . It does many of the same things that a person does: it talks and walks and thinks . . . It even has a temporal duration. But only a brief one, for it does not last long’ (p. 76). He then goes on to argue that person-stages thus conceived do indeed exist and constitute the temporal parts of persons. The first step in his argument is this: ‘First: it is possible that a person-stage might exist.

Suppose it to appear out of thin air, then vanish again’ (p. 76). But, I would contend, all that Lewis has really succeeded in doing here is to introduce us to the fanciful notion of a very short-lived person (i.e. to the idea that a person might in some miraculous way be conjured into and out of existence in a trice), and as such he has failed to introduce us to a category of independently individuable entities in terms of which a criterion of diachronic identity for persons might be non-circularly specified.

‘spatial part of a tomato’ is obviously ambiguous as it stands. On the one hand it may be taken to mean ‘part (i.e.

component or constituent) of a tomato which has spatial characteristics’—under which interpretation one of a tomato's seeds, say, will count amongst its ‘spatial parts’. But on the other hand it may be taken to mean something like

‘object consisting at any time of the matter enclosed by a geometrically defined surface not extending beyond the outer skin of a tomato’—under which interpretation a quarter-inch cross-section through the middle of a tomato will count amongst its ‘spatial parts’. However, it seems evident that the notion of a temporal part of a tomato, if it is to play any distinctive theoretical role in an account of the persistence of something like a tomato, can only be supposed to be modelled on the second of these two senses of ‘spatial part’: a temporal part of a tomato has—if, indeed, this is possible—to be thought of as a temporal ‘cross-section’ or ‘slice’ of a tomato. For if by a ‘temporal part’ of a tomato one merely meant, by analogy with the first sense of ‘spatial part’, a constituent of a tomato which has temporal characteristics, then a tomato's spatial and temporal parts in these senses would be precisely the same sorts of items (items such as its seeds). But—unfortunately for the temporal parts theorist—it seems clear that it is only the spatial and temporal parts of a tomato in this rather jejune first sense which qualify as objects that are individuable and identifiable independently of the tomatoes of which they are parts.

Against this claim, it may be perhaps urged that if we are presented with a single spatial slice (or ‘spatial cross-section’) of a tomato on a plate, then we can individuate and identify this slice without being in any position to say from which tomato it has been cut. But this objection trades on an ambiguity in the notion of a spatial ‘slice’ (or ‘cross-section’). By a spatial ‘slice’ of a tomato one may either mean a particular type of spatial part of a tomato in the second sense explained above, or else one may mean something like ‘object obtained by actually cutting twice through a tomato in two approximately parallel planes’. The spatial parts of a tomato in our second sense of ‘spatial part’ do not include slices of it in this second sense of ‘slice’, however. There is no possibility of identifying slices of the two different kinds—geometrical slices and physical slices, as we might respectively call them. To see this we only have to consider the different capacities which the two kinds of slice possess to undergo certain sorts of temporal change. For instance, a physical slice of a tomato can clearly undergo all manner of changes in shape, whereas the very nature of a geometrical slice is defined in part by its shape. (In the case of a physical slice, shape only enters into the explanation of how the slice is produced.) Again, if the material contents of a tomato are rearranged, the matter contained in one of its geometrical slices may well alter considerably

(as various seeds, quantities of juice, and so on alter their locations within the tomato). No comparable possibilities for changing its constituent material arise in the case of the physical slice, however. But these and related facts also serve to show that geometrical slices, unlike physical ones, cannot be individuated independently of the whole objects of which they are slices: thus a geometrical slice of a tomato is partly individuated by reference to its relative position within the tomato, which it evidently cannot alter. Moreover, it is clearly geometrical slices rather than physical ones which must provide the spatial analogue for the supposed temporal parts or ‘slices’ of persisting objects (since, quite apart from anything else, nothing very obviously corresponds in the temporal case to the physical act of cutting which creates a physical spatial slice).

Now, if I am right in saying that the spatial parts of a tomato in our second sense of ‘spatial part’ are objects which cannot be individuated or identified without reference to the tomato of which they are parts, and am also right in supposing that the notion of a temporal part of a tomato can only (at best) be seen as analogous to this second sense of

‘spatial part’, then it would seem to follow that even if we do countenance such entities as the temporal parts of tomatoes, they will not be fit items in terms of which to attempt to frame a non-circular criterion of diachronic identity for tomatoes.¹⁵⁴In reply to this it might perhaps be urged that the notion of a temporal part of a tomato (or, at least, the notion of an instantaneous temporal part of a tomato) only presupposes a synchronic identity criterion for tomatoes and hence that it can be invoked non-circularly for the

154 By now some readers may have wanted to accuse me of taking too narrow a view of the temporal parts approach, and in particular too narrow a view of what a temporal part or stage would have to be. Thus Sydney Shoemaker, a prominent adherent of the approach, has written: ‘Person-stages can be thought of as “temporal slices”, not of persons, but of the histories or careers of persons. [Or] one might think of a momentary stage as a set of property instantiations . . . Or one can think of a momentary stage as an ordered pair consisting of a thing and a time’ (‘Personal Identity: A Materialist's Account’, in Sydney Shoemaker and Richard Swinburne, Personal Identity (Oxford:

Blackwell, 1984), 75). However, the second of these suggestions would reduce the temporal parts approach to the property instantiation approach, while the first and third would transparently make the individuation of ‘stages’ parasitic upon that of the persisting objects whose diachronic identity they were invoked to account for. Such circularity does not, it is true, worry Shoemaker, who elsewhere concedes that by his own account the persistence-conditions of continuants cannot be non-circularly specified (see ‘Identity, Properties, and Causality’, in Sydney Shoemaker, Identity, Cause, and Mind (Cambridge: Cambridge University Press, 1984) ). But I cannot agree that a circular specification of persistence-conditions, however non-trivial, may legitimately be presented as an account of what persistence consists in. (Colin McGinn also makes this point in his review of Identity, Cause, and Mind in the Journal of Philosophy, 84 (1987), 227–32.) So my answer to the objection raised in this note is that I adopt the interpretation of the temporal parts approach which I do because it seems to me to be the least unpromising on this score.

purposes of a diachronic criterion. But again I would reply, as I did when a similar move was made on behalf of the property instantiation approach, that one is not entitled to presume that synchronic and diachronic identity criteria for objects like tomatoes are independently intelligible. The temporal parts approach seemed initially to have an advantage over the property instantiation approach precisely on this score: but what we have now seen is that in reality the two approaches are in the same boat—and it is a sinking one. (In case, however, there are any lingering doubts concerning the circularity issue, I should remark that we shall return to it in Chapter 7 below.)