Here is a valid argument:
Matter survives substantial change.
It is not possible that there exist two substances of the same species with the very same matter.
If matter survives substantial change, it is possible to have two substances of the same species existing at different times with the very same matter.
So, it is possible to have two substances of the same species existing at different times with the very same matter. (1,3)
If presentism is not true, and it is possible to have two substances at different times existing with the very same matter, it is possible to have two substances of the same species existing with the very same matter.
So, if presentism is not true, it is possible to have two substances of the same species existing with the very same matter.
So, presentism is true. (2, 5)
Let’s think about the premises. I think Aristotle is committed to (1)—it’s essential to his solution to the alleged problem of change. Claim (2) is a famous Aristotelian commitment. Claim (3) is very, very plausible—surely matter moves around in the world, and it is possible to set things up so that I have the same atoms that Henry VIII had at some point in his life. Claim (5) follows when we note that the only two plausible alternatives to presentism are eternalism and growing block, and on both views if two substances of the same species exist at different times with the very same matter, then at the later time it is true that they both exist simpliciter.
However, given that there is excellent Aristotelian reason to deny presentism, the above argument gives some reason for Aristotelians to deny (1) or (2). Or to be more radical, and just deny that there is any such thing as the “matter” of traditional Aristotelianism.
I am not a knowledgable enough Aristotelian to know, but is claim 2 made implicitly assuming a qualification like adding "simultaneously" at the end? Was the claim was ever made diachronically, or was contemporaneity always assumed, making it more self-evident?
ReplyDeleteIf, like many ancients, Aristotle had believed the legend of the Phoenix, might he not have accepted that if such a bird dissolved into ashes as a male and was reconstitued as a female centuries later, that there was a substantial difference in the technical sense? I ask because I really have no idea.
Good points!
ReplyDeleteTime travel cases will be problematic even with "simultaneously". Suppose the female phoenix travels back in time to meet the male phoenix, and both are made of the same matter. But of course whether time travel is possible is controversial.
A "simultaneously" qualifier may also run into trouble with relativity theory, though I think we could say "simultaneously in at least one reference frame" to take care of that.