Wolfgang Schwarz

Temporal Parts and Restrictions on Fusions

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'.)

Anyway, back to (1). I believe that (1) is a very obvious and commonsensical truth. Or at any rate, it is a philosophical expression of a very obvious and commonsensical truth. So at least as far as (1) is concerned, I don't agree that common sense is on the side of endurantism.

Consider a caterpillar who turns into a butterfly at some time t. I guess most people would agree that it makes sense to speak of one animal here that first was a caterpillar and later a butterfly. Let's call this individual 'the insect'. It also seems uncontroversial that at the early times of the insect's life there exists a caterpillar. (Let's call it 'the caterpillar'.) The caterpillar ceases to exist at time t. So it is not identical with the insect, which continues to live after t. How are the caterpillar and the insect related? the caterpillar is a temporal part of the insect.

Another obvious example are stars and red giants: A red giant and the star that turned into it (but still continues to exist) are related by the temporal-part relation. If you see that the caterpillar is related to the insect in a similar way as the red giant to the star, you have understood my notion of temporal parthood.

How could one deny (1)? The only way I can see is to impose bizarre restrictions on mereology. Peter van Inwagen e.g. simply claims that there is no such thing that first was a caterpillar and later a butterfly. That is, on his view the insect doesn't exist. Neither does the star. But that certainly is not very commonsensical.

In fact, (1) immediately follows from relaxing the constraints on mereological fusions: If A is an object that entirely exists before B, and if the fusion of A and B exists, then A is a temporal part of that fusion (and so is B). So one can get rid of temporal parts only by rejecting that things that exist after each other (perhaps even things that do not exist simultaneously) can have a fusion. I would say that this contradicts common sense, and commits the endurantist to spelling out and motivating his constraints on fusions -- and anyone who has read van Inwagen should be hesitant to do this.