I was thinking about something Tillman said last class - that the VI/Merricks view meant that apple trees but not apples exist - and this seems like a serious problem for the view. Apple trees exist because the collective activity of an apple tree's parts somehow constitute a life, and it seems that the collective activity of an apple seed's parts should also constitute a life - after all, the seed grows into the tree, and if the seed is not alive, then neither is the tree. So seeds exist.
The problem here is apples.
Apples aren't alive (at least, not by any biological definition) and they are just as causally irrelevant as baseballs - the scent, taste, shape, crunchiness, hardness, etc., of an apple can be explained solely in terms of the collective activity of its atoms... So apples certainly don't exist.
But apple seeds do, and apple seeds are part of an apple - in fact, seeds are the very reason that apples are produced! It certainly wouldn't be reasonable to think that an apple doesn't exist but a part of an apple (the seeds) does exist, as if it were possible for some apple parts to exist by merit of their life and other apple parts to only be atoms arranged apple-wise. That's strange. There would have to be a really good reason to actually believe that.
To sum up: If causal relevance is the only factor VI/Merricks has to offer in determining whether something exists, then trees and seeds exist but fruit (which contains seeds) doesn't exist, because the fruit is causally irrelevant. And that makes no sense.
I think causal relevance just isn't enough to decide whether something exists. What does everyone else think?