- Our question of overlap of worlds parallels the this-worldly problem of identity through time; and our problem of accidental intrinsics parallels1 a problem of temporary intrinsics2, which is the traditional problem of change. Let us say that something persists iff, somehow or other, it exists at various times; this is the neutral word. Something perdures if it persists by having different temporal parts, or stages, at different times, though no one part of it is wholly present at more than one time; whereas it endures if it persists by being wholly present at more than one time. Perdurance corresponds to the way a road persists through space; part of it is here and part of it is there, and no part is wholly present at two different places. Endurance corresponds to the way a universal3, if there are such things, would be wholly present wherever and whenever it is instantiated. Endurance involves overlap: the content of two different times has the enduring thing as a common part. Perdurance does not4.
- (There might be mixed cases: entities that persist by having an enduring part and a perduring part. An example might be a person who consisted of an enduring entelechy ruling a perduring body; or an electron that had a universal of unit negative charge as a permanent part, but did not consist entirely of universals5. But here I ignore the mixed cases. And when I speak of ordinary things as perduring, I shall ignore their enduring universals6, if such there be.)
- Discussions of endurance versus perdurance tend to be endarkened by people who say such things as this: "Of course you are wholly present at every moment of your life, except in case of amputation. For at every moment all your parts are there: your legs, your lips, your liver...." These endarkeners may think themselves partisans of endurance, but they are not. They are perforce neutral, because they lack the conceptual resources to understand what is at issue. Their speech betrays — and they may acknowledge it willingly — that they have no concept of a temporal part. (Or at any rate none that applies to a person, say, as opposed to a process or a stretch of time.) Therefore they are on neither side of a dispute about whether or not persisting things are divisible into temporal parts. They understand neither the affirmation nor the denial. They are like7 the people — fictional, I hope — who say that the whole of the long road is in their little village, for not one single lane of it is missing. Meaning less than others do by 'part', since they omit parts cut crosswise, they also mean less than others do by 'whole'. They say the 'whole' road is in the village; by which they mean that every 'part' is; but by that, they only mean that every part cut lengthwise is. Divide the road into its least lengthwise parts; they cannot even raise the question whether those are in the village wholly or only partly. For that is a question about crosswise parts, and the concept of a crosswise part is what they lack. Perhaps 'crosswise part' really does sound to them like a blatant contradiction. Or perhaps it seems to them that they understand it, but the village philosophers have persuaded them that really they couldn't, so their impression to the contrary must be an illusion. At any rate, I have the concept of a temporal part; and for some while I shall be addressing only those of you who share it.
- Endurance through time is analogous to the alleged trans-world identity of common parts of overlapping worlds; perdurance through time is analogous to the "trans-world identity," if we may call it that, of a trans-world individual composed of distinct parts in non-overlapping worlds. Perdurance, which I favour for the temporal case, is closer to the counterpart theory which I favour for the modal8 case; the difference is that counterpart theory concentrates on the parts and ignores the trans-world individual composed of them.
- The principal and decisive objection against endurance, as an account of the persistence of ordinary things such as people or puddles, is the problem of temporary intrinsics9. Persisting things change their intrinsic properties. For instance shape: when I sit, I have a bent shape; when I stand, I have a straightened shape. Both shapes are temporary intrinsic properties; I have them only some of the time. How is such change possible? I know of only three solutions.
- (It is not a solution just to say how very commonplace and indubitable it that we have different shapes at different times. To say that is only to insist — rightly — that it must be possible somehow. Still less is it a solution to say it in jargon — as it might be, that bent-on-Monday and straight-on-Tuesday are compatible because they are 'time-indexed properties' — if that just means that, somehow, you can be bent on Monday and straight on Tuesday.)
- First Solution: Contrary to what we might think, shapes are not genuine intrinsic properties. They are disguised relations, which an enduring thing may bear to times. One and the same enduring thing may bear the bent-shape relation to some times, and the straight-shape relation to others. In itself, considered apart from its relations to other things, it has no shape at all. And likewise for all other seeming temporary intrinsics10; all of them must be reinterpreted as relations that something with an absolutely unchanging intrinsic nature bears to different times. The solution to the problem of temporary intrinsics11 is that there aren't any temporary intrinsics12. This is simply incredible, if we are speaking of the persistence of ordinary things. (It might do for the endurance of entelechies or universals13.) If we know what shape is, we know that it is a property, not a relation.
- Second Solution: The only intrinsic properties of a thing are those it has at the present moment. Other times are like false stories; they are abstract representations, composed out of the materials of the present, which represent or misrepresent the way things are. When something has different intrinsic properties according to one of these ersatz other times, that does not mean that it, or any part of it, or anything else, just has them — no more so than when a man is crooked according to the Times, or honest according to the News. This is a solution that rejects endurance; because it rejects persistence altogether. And it is even less credible than the first solution. In saying that there are no other times, as opposed to false representations thereof, it goes against what we all believe. No man, unless it be at the moment of his execution, believes that he has no future; still less does anyone believe that he has no past.
- Third Solution: The different shapes, and the different temporary intrinsics14 generally, belong to different things. Endurance is to be rejected in favour of perdurance. We perdure; we are made up of temporal parts, and our temporary intrinsics15 are properties of these parts, wherein they differ one from another. There is no problem at all about how different things can differ in their intrinsic properties.
Footnote 1: Lewis says that he’s indebted to "Armstrong (David) - Identity Through Time" in this regard, “and to Johnston”, whose terminology he follows. The only reference to a “Johnston” in the bibliography of "Lewis (David) - On the Plurality of Worlds" is to the PhD dissertation “Particulars and Persistence” by Mark Johnston – presumably Mark Johnston.
Footnote 3: I take issue with this in a footnote to "Hawley (Katherine) - David Lewis on Persistence".
Footnote 4: It does, I think, but in different ways. Part of the perdurantist explanation of Fission (Click here for Note) involves shared stages, so two spacetime worms overlap for a period of their existence.
Footnote 7: I don’t think this analogy is helpful, or even very clear. The “darkeners” seem to have a concept of spatial parts (the bodily organs) but not temporal parts. The analogy seems to be of those who have a concept of lengthways parts (the lanes) but not of crossways parts (sections of road, most of which are outside the small village). It all seems rather forced.
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