Saturday, November 24, 2007

Arbitrary Persistence

If one asks whether A and B (objects existing at two different times, or possible worlds, say) are really one and the same object, is this a substantive metaphysical question? I think it is not. Consider the following illustration:

This is how an armless person persists through time. S1 is the momentary stage that exists at t1, and S2 likewise at t2. C is the complete aggregate of all the momentary person-stages from t1 to t2. Now, one might apply the name 'A' at t1, and 'B' at t2, and ask whether A is B. But there are no interesting questions to ask here. It's trivial that S1 is not S2, if that's what we mean. Or, if we instead mean to refer to the temporally extended object C both times, it is similarly trivial that C is identical to itself.

Note that we may similarly construct gerrymandered objects out of completely unrelated temporal parts. For any two distinct stages whatsoever, it is trivial that (1) they are not themselves numerically identical; and (2) we may call them both temporal parts of some larger aggregate. (If you don't like talk of aggregations, we can restate the point in terms of temporal counterparts. Any two stages are counterpart-related by some criterion or other, and our choice of criterion is metaphysically arbitrary.) We merely have practical reasons for carving the world up in some ways rather than others. Gerrymandered objects may be less useful to talk about, but that's not to impugn their ontological status.

Maybe you don't like any kind of 4-dimensionalism or "temporal parts" talk. That's okay, we can restate the point in the language of enduring 3-d objects. We simply need to say that there are arbitrarily many objects coinciding in any given region of space, for all the various possible "persistence criteria" we might want to apply across times. Consider the famous example of a clay statue. Can it survive being turned to gold by Midas' touch? Well, the statue can, but the clay can't. Conversely, the lump of clay can survive being squished into a nondescript blob, but the statue cannot. And we might just as well choose to say there is an object there that "endures" just in case it turns into a bird and flies away. Why not? It's not as though all this persistence talk is reflecting anything deep about the world. We could apply any criteria we want; it's all mere convention.

The alternative view is what Ted Sider (in his (2001) 'Criteria of Personal Identity', p.194) calls "chaste endurantism", i.e. the conjunction of claims (1) objects - no mere temporal parts - are wholly present at multiple moments, and (2) "distinct entities never coincide". But the case of the statue and the clay suggests that this position is a non-starter. There are various criteria we might use to determine whether an object counts as persisting into the future under any given scenario, and no reason to think that any one of these is the only legitimate or "true" criterion.

So I tend to think that the identity facts, such as they are, do not much matter. Indeed, we may completely describe a scenario without talking about the identities of the things in it at all. We would then know all there is to know about how the world (scenario) is; the remaining question is merely how to describe it -- which persistence conditions to apply, or which temporal aggregates to talk about.


  1. Your view gets makes counting facts weird. Someone asks: how many people attended the hour long lecture? In your view, there is no robust reason to say fifteen over fifteen million or fifteen trillion--metaphysics, the fabric of reality, just doesn't have anything to say about this question. But intuitively that's wrong. The answer is fifteen. Or this: how many people have you dated in your life? Please let it be less than a million.

    Let me put it another way. This seems to be a good principle: S is true only if it is metaphysically settled that S, that is only if metaphysics tells us that S. With this principle, you are an error theorist about counting. There are no truths about counting, or only very few. That seems very strange.

    If you counter that there are practical reasons to count one way rather than another, let me re-counter by asking: why? Why does it seem that only fifteen people have attended the lecture? What could make one way of counting better than another--even practically better--if there are no metaphysical facts underlying them.

  2. What makes "one way of counting better than another"? That it serves our purposes, and helps us to get around in the world successfully. For example, our way of counting had better enable us to provide ample chairs so that the lecture attendees (all fifteen trillion of them!) may sit. There doesn't seem anything too mysterious about this sort of matching-up process.

    Similarly, if I tell you I've dated a million people, you're apt to get a very misleading impression. You may draw mistaken inferences even about merely qualitative historical facts.

    For practical purposes, it's the qualitative nature of the world that matters. (I'll still have done a good job in providing sufficient chairs, even if "two" of them are actually just one chair -- a time-traveling chair, say -- that happens to be co-located at two spatial regions at once!) So, we adopt counting conventions that make it easy for us to convey information about the qualitative nature of the world. I'm not sure why the underlying metaphysics should be thought to have any practical relevance at all.

  3. I suppose it is trivial that we could define a word as a different thing and it would then have a differnet meaning. But unlike in many other cases I think that there is somthing under this that a person asking the question might be trtying to get at. I.e. I think there is somthing worth discussing regarding how time connects things compared to how space connects things, and the degree to which we are rational in sacrificing things now for things later (asuming some level of selfishness).

  4. Interesting post Richard!

    Would you take the same view on object-composition? Sure, we can call that (*points to cow*) conglomeration of particles a "cow", but we could equally give that (*points to cow foot, half of my computer speaker, and my right kidney*) conglomeration of particles its own name. Neither is more "real" than the other.

    That seems analogous to me, but I'm far less inclined to take your view on it. Would you agree?

    I guess the real question is whether there's more "unity" - in some sense - for some conglomerations, either across time, or between particles at a time, than there is for others. What "in some sense" means is obviously up for dispute, but I think there's something wrong with this kind of reductionism.

  5. Hi Alex, I'm interested in the "unity" issue you raise. But I see this as independent of the question what exists. (Your cow-kidney conglomeration is perfectly real. It's just not very unified or useful to talk about.)

  6. I think this is a general problem of simplifying a very complicated reality to something that we can think and talk about. It applies to identifying objects at any instance of time, just as much as identifying 4-dimensional objects. Such assignments will rarely be perfect, but that's no reason to claim that some assignments aren't more true than others. Descriptions of reality that suit our purposes will tend to be more true because if they weren't they wouldn't help us very much, but I don't think "serving our purpose" and true are equivalent.

  7. I tend to sympathise with (what I take to be) your line of argument, Richard. Please correct me if I'm wrong. I take it to have two components.

    First, questions of persistence over time and mereology are not questions about what the world is like but rather how to describe it.

    Second, claims about persistence are false but useful. I am not the same person as the qualitatively very similar person existing seconds ago.

    The second thesis has enormous implications for moral responsibility and the value we attach to our lives. Are you happy to accept them?


  8. Hi Marco, that's one way to put it, though persistence claims could be literally true depending on how we interpret them. (E.g. it's literally true that S1 and S2 are both temporal parts of a single, self-identical aggregate C.) But yeah, on the commonsense understanding, I'd say they're all false.

    I don't think this has the ethical implications you imagine, though. We can replace the strict metaphysical notions with looser, more practical ones, and it's the latter that really matter for moral philosophy.

  9. Hi Richard,
    Yes, I was a bit quick. I do have the suspicion that thinking of persisting people in this way has implications for responsibility and our model of justice. I'm just not very clear about it.

    Temporal part p1 commited murder. We regard temporal part p2 as responsible because p2 shares many of the character traits that led p1 to murder. But our response should only be one of trying to reform p2. I don't think that retribution against p2 makes sense once we admit that p2 didn't murder anyay.

    I suppose the question depends on whether we should think of people at t as their temporal part present there or the aggregate partially present there. Just as a box that is partially located at L1 and blue at a part at L2 is not therefore blue at L1, shouldn't we say an aggregate one of whose parts has the property of having murdered does not therefore have the property now of having murdered?

  10. macro,
    I don't think retribution is valid anyway, But if I did then I think that person at t2 could be considered to not have responsibility for actions of t1.
    Note also however that the law is also about discouraging others from commiting the same crime etc.

  11. Genius -
    I, too, think retribution is unjustified. But my point here is that there is an independent argument against it from "nihilism about persistence". I'm just trying to get a handle on the fact that the view has implications.

  12. Marco - "I suppose the question depends on whether we should think of people at t as their temporal part present there or the aggregate partially present there."

    Yeah. And it seems that it's the aggregate person we're interested in, for practical matters. Even if their present part is not a murdering part, still it can be that they - the temporally extended whole - are a murderer, in virtue of having a past murdering part. (They do have the property, now and always, of having a temporal part that murders.)


Visitors: check my comments policy first.
Non-Blogger users: If the comment form isn't working for you, email me your comment and I can post it on your behalf. (If your comment is too long, first try breaking it into two parts.)

Note: only a member of this blog may post a comment.