Posts on: Persistence
Suppose tonight you will fission into two persons. One of your
successors will wake up Mars and one on Venus. There are then two
possibilities for how things might be for you tomorrow: you
might wake up on Mars, and you might wake up on Venus. These are
distinct centered possibilities that do not correspond to distinct
uncentered possibilties. There is just one possibility for the
world, but two possibilities for you. Indeed, the two possibilities
are two actualities: you will wake up on Mars, and you will
wake up on Venus. It is tempting to go further and say that there are also two
possibilities for you now. I want to discuss three quite
different reasons for making this move.
I believe that the so-called problems of intrinsic change and accidental intrinsic properties are real problems. But I believe that their names are misleading, and that they have nothing to do with whether or not we construe properties as sets of things or as functions from worlds and times to sets of things.
Suppose we do the latter, and we also endorse counterpart theory and temporal parts theory. The property of being bent is a function that maps world-time pairs to sets of things. These things are temporal parts of world-bound individuals, ordinary fusions of particle segments, just like us, except that they are smaller along the time axis and all bent. This is a perfectly reasonable and common-sensical view, I believe (but of course I'm biased), and I don't think Lewis has any reason to reject it as turning properties into relations. There is after all a simple equivalence between being bent construed as a function and being bent construed as a Lewisian set: the set is the union of the range of the function; the function indexes all members of the set by their world and time.
OK, back. The bike trip was cool.
Meanwhile, in the comments, David Sanford raised the question whether sets gain and lose members. One might say yes, for arguably
*) If y is the set of all Fs, then x is a member of y iff x is F.
Since the wall in front of me is white and there is a set of white things, by (*), the wall is a member of that set. But last year, that wall was green, and surely it was never the case that something green was a member of the set of white things; so the wall was not a member of that set last year. It follows that the set of white things gained a member when I painted the wall.
Robbie Williams pointed out that in my recent musings on worms and stages, I ignore the following straightforward characterizations:
Worm Theory: the semantic value of predicates like "rabbit" is a set of 4D worms.
Stage Theory: the semantic value of predicates like "rabbit" is a set of 3D stages.
He's right. I believe that these theories both cannot work, so I don't want to define stage and worm theory that way.
According to the Stage View, ordinary objects are temporally unextended timeslices. "Ted sleeps" is true iff the present Ted-stage sleeps.
What if there is no present stage, as with "Socrates is wise" and "Socrates exists"?
The question is not what to say about "Socrates was wise" and "Socrates did exist". These are true because at some time in the past, there is a wise Socrates stage (see pp.27f. of Ted Sider's Stage paper). The problem is the tenseless "Socrates is wise".
I don't share Lewis's strong intuitions that shape properties must be purely intrinsic rather than time-indexed. For me, the argument from intrinsic change works much better with certain relations, in particular mereological relations and identity.
Suppose x is part of y at time t1, but not at t2. Perdurantists can say that the temporal part of x at t1 is a part simpliciter of the temporal part of y at t1. Time-indexers will say that the whole of x stands in the part-at-t1 relation to the whole of y, where this relation is not analysable in terms of non-indexed parthood: time-indexed parthood is all there is. But no! Subsets are parts simpliciter of sets, battles are parts simpliciter of wars, the story of the Trojan War is a part simpliciter of the Illiad, geometry is a part simpliciter of mathematics, XPath is a part simpliciter of XSLT, and so on. These things are not part-at-time-related, but part-related.
I haven't really checked the literature, but is there a general agreement on why the problem of temporary intrinsics is a problem of intrinsics and not a general problem about temporary properties? Certainly it is just as impossible for a thing both to have and to lack an extrinsic property as it is impossible for intrinsic properties. A while ago, I said that perhaps for temporary extrinsics, the problem is not really a problem because the relational answer is the obviously correct one: having extrinsic property F at time t clearly means being F-related to t. But in fact that doesn't sound obvious at all. Does being an uncle relate people to times? It seems not. It seems only to relate them to other people. If one intuits that being round is not a relation to a time, I don't see why one wouldn't similarly intuit that being an uncle is not a relation to a time.
The problem of intrinsic change is often put in misleading terms, like: "how is it possible for a thing to have incompatible intrinsic properties at different times?", or: "how can I be first bent and then straight?" Putting the problem this way invites wrong kinds of answers, like:
- There really is no problem here. Why should things not have incompatible properties, as long as they
have them at different times?
- Well, a thing can change its instrinsic properties by consisting of a substratum to which different properties attach at different times.
- How can I be first bent and then straight? Why, by standing up.
When I first read Lowe's proposed solution, I thought what he offers belongs to this class of answers that don't answer the real problem. In fact, his answer looks much like the third one above: How can I be first bent and then straight? By having parts, such as legs and a torso, which can change their spatial arrangement. Sure. But does that answer the problem?
When first introduced to the distinction between three- and fourdimensionalism and between perduranitsm and endurantism, many, myself included, have the feeling that both are valid ways of looking at the same reality and hence that at bottom they must be somehow equivalent or inter-translatable.
I still believe some of this. Consider for example the question of interpreting temporal predications. Endurantists say that "x is F at t" is true iff (the whole of) x stands in the F-relation to t, or iff x instantiates-at-t F, or something like that. As a perdurantist, I need not deny that. Rather, I have a further analysis of what it means to stand in the F-relation to t, or to instantiate-at-t F: it means to have a temporal part located at t which is F. Similarly, I needn't deny that I am wholly present right now. Applying the perdurantist analysis, what this claim says is that I -- the entire worm, with all his spatial and temporal parts -- have a temporal part which is present right now. Perhaps I could even try to make sense of claims like "people don't have temporal parts" by appealing to restricted quantification. But somewhere around this point the translatability comes to an end. Endurantists usually build the rejection of perdurantism into the very heart of their account, and it is certainly uncharitable to re-interpret this rejection so that it is after all compatible with what it rejects. (Here is something odd, by the way: how can it be uncharitable to interpret someone's utterances in such a way that they come out true rather than in a way in which they are false?)
There are lots of distinctions between perdurantism and endurantism (or better, between different perdurantisms and endurantisms). Here I want to talk about the following perdurantist claim:
1) Some things (that are not events) have temporal parts.
This does not imply that ordinary things like buildings and persons have temporal parts. And even if one believes the latter, it is still perfectly coherent to reject any account of intrinsic change in terms of temporal parts, or reject an account of personal identity in terms of (properties of) temporal parts, or reject an account of persistence in terms of temporal parts, or reject whatever else temporal parts are used to account for. It is also okay to accept only some of these accounts and reject others. (I for example am a perdurantist who rejects the account of persistence in terms of temporal parts: not only can I say what it is to persist through time without mentioning temporal parts, I even believe that it is possible for a thing to exist through time without having temporal parts.) That's how we get so many perdurantisms and endurantisms. (I think it would be very helpful if people discussing this matter exactly said what they say on each of these issues rather than vaguely asserting that, e.g., things are 'wholly present at different times'.)
Well, what do I mean by "extended"? If "extended" means
"having parts", nobody thinks that extended things lack parts. I guess
what I mean is "existing at several different (space-, time- or spacetime-)
coordinates". For instance, I find it hard to understand how something
could cover all of Berlin without having any part that covers Kreuzberg. I
see that this is precisely how immanent universals are supposed to exist,
but that doesn't help me much, because I find it equally puzzling here.
Perhaps I was wrong when I said that those who
claim that perdurantism is contingent think that things could undergo
intrinsic change without having temporal parts. I've just reread
Haslanger's and Lewis' remarks, and these appear to be compatible
with the view that only things that don't change might endure. For
example, Lewis only mentions the possibility that the spatial parts of a
spinning sphere might persist by enduring. And maybe those parts don't
ever change their intrinsic properties. Probably even the entire sphere
doesn't, because if you copy a particular sphere stage and rotate the copy
by 180 degrees, you still have an exact intrinsic duplicate of the original
stage. This would explain why Lewis doesn't announce a big change of view,
because he always accepted that some special entities, namely universals,
might endure.
My only complaint then is that this doesn't turn perdurantism into a contingent theory of intrinsic change (rather than persistance). And I still find it difficult to understand how extended things could lack parts.
Several people have claimed that perdurantism is only contingently true, or at
least a posteriori: Mark Johnston expresses something like this at the end
of "Is There a Problem about Persistence?"; Sally Haslanger in "Humean
Supervenience and Enduring Things"; Frank Jackson in section 2 of
"Metaphysics by Possible Cases"; and David Lewis in section 1 of "Humean
Supervenience Debugged".
One of the arguments for this claim seems to be that both perdurantism and
endurantism are to some degree intelligible, which is why philosophers
still disagree about the issue. I find that strange. Philosophers also
disagree about the existence of universals, arbitrary mereological fusions,
possible worlds, and numbers. Are these also contingent matters?
It is easy to overlook that David Lewis has revised his worm view of ordinary things in 'Tensing the Copula', Mind 111 (2002). Here is the passage (p.5):
In talking about what is true at a certain time, we
can, and we very often do, restrict our domain of discourse so as to
ignore everything located elsewhere in time. Restricted the domain in
this way, your temporal part at t_1 is deemed to be the whole of
you. So there is a good sense in which you do, after all, have *bent simpliciter*.
In other words: Terms for ordinary things are indeterminate. They don't always pick out worms. Sometimes they pick out segments, and sometimes just stages, depending on the contextually determined domain of discourse.
I think this is an improvement over the worm theory. Is it general enough? Lewis says that our terms pick out the sum of all those temporal parts of the relevant worm that are inside the domain of discourse. But don't we also attribute bent-simpliciter to the whole of me in "I'm bent now, but I wasn't bent yesterday"? Yet here the domain contains yesterday's parts as well.