Van Inwagen thinks that a plurality of xs composes something if and only if either there is only one thing among the xs or the xs have a life together.
He also agrees that the fundamental particles making up a cell in a multicellural organism have a life together, and so there are cells.
Here is a problem. The following seem true:
It is possible to have two overlapping cells in a multicellular organism neither of which is a part of the other.
The cells of a multicellular organism together with any intercellular fundamental particles have a life together.
Why think (1)? Because, first, conjoint twins show that multicellular organisms can have “proper overlap”: i.e., they have a part in common but neither is a part of the other, and it seems hard to deny that cells, too, could in principle be like that. Second, it seems plausible that mid-way through a process of mitosis we have two cells that properly overlap.
It seems hard to deny (2), assuming there are cells.
But now consider a multicellular organism which happens to have two overlapping cells. Its cells, together with any intercellular fundamental particles, have a life together. Hence, by van Inwagen’s famous account of composition, the cells and the intercellular fundamental particles compose something. But van Inwagen’s definition of composition includes a no-overlap condition: if the xs compose y, no two xs overlap. And yet in our case we have life and overlap.
What should van Inwagen do? One move would be to weaken the Special Composition Question. Instead of asking when the xs compose something, he could ask when non-overlapping xs compose something. But that makes his view rather less informative than we might think, if overlap between cells is fairly common. Presumably in a body of my size, at any given time, mitosis is occuring in a number of cells (I haven’t done the math, but it seems likely).
5 comments:
Are photons fundamental particles? Because during photosynthesis in a plant cell, multiple photons overlapping in the same space hit the leaf cell's chlorophyll to drive chemical reactions. So we don't need cells to have the overlap question, just bosons.
Or perhaps, contrary to appearances, Conjoined Twins do not actually share any of their parts: https://link.springer.com/article/10.1007/s11098-026-02581-3 ;)
I am friendly to that suggestion myself, but I don't think it is open to van Inwagen to think that this is necessarily true. Here's why. Van Inwagen thinks facts about composition depend on the arrangement and causal interrelation of parts. But one could, at least in principle, have perfectly symmetric twinning and perfectly symmetric conjoined twins. Now, if he were a hylomorphist like me, he could say that it just is a fact as to which parts are informed by which form. But he's not. He's a non-Aristotelian naturalist.
If van Inwagen were friendly to the kind of solution on which there is a fact as to which particle belongs to which twin, I think by the same token he would be friendly to an epistemicist solution to other vagueness issues surrounding his organicist theory. But he's not.
Maybe one could have a vagueness story according to which it is definite that each particle is a part of one twin or the other but not both, but it can be vague as to which twin it is a part of. That feels somehow deeply unappealing to me.
I wasn't clear. The relevant overlap is mereological overlap, not spatial overlap. Mereological overlap means having a part in common. Two particles being in one place is only spatial overlap.
Two thoughts.
In the post, I objected to the weakening of the life answer on the grounds that in us there will pretty much always be overlapping cells. But I think that's not a problem. Even when there are overlapping cells, the weakened answer is informative. It says (a) that my simple particles compose something, and (b) that those of my cells that don't overlap another cell plus the simple particles in the cells that suffer overlap plus the simple intercellular particles compose something.
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