Parts and priority

Schaffer says that pluralists think that parts are ontologically prior to their wholes. But this seems wrong, even as restricted to bottom-up pluralists who think the fundamental realities are microphysical.

For consider that (assuming the materialism that bottom-up pluralists typically do) I am a part of the Milky Way Galaxy (both a part-at-a-time and an atemporal part). But it seems quite wrong to say that I am ontologically prior to the Milky Way. My fundamental particles may be ontologically prior to the Milky Way, but I am not.

Further, many bottom-up pluralists accept classical mereology. But now while it seems right, if I put myself in the mindset of a typical non-Aristotelian metaphysician, to say that my atoms, molecules, cells, and organs are prior to me, it seems wrong to think that “weird scattered parts” are prior to me. Imagine for instance ordering all my molecules from bottom to up, and then take the fusion of all the even-numbered molecules. That fusion exists and is a part of me by classical mereology, but it doesn’t seem like the sort of thing that’s prior to me. It seems to be something that emerges from my simples in parallel with me at best.

If this is right, then what are the priority relations between objects for bottom-up pluralists? For unrestricted compositionalists, I think the natural suggestion is this: The simples are prior to all the wholes made of them, and that’s the only priority relation there is. This has some counterintuitive results. For instance, it seems plausible that my molecules are prior to me, or that the individual people of France are prior to France. That’s probably a bullet that the unrestricted compositionalist should bite. For one of the primary arguments for unrestricted composition is worries about vagueness and continuous series, and as soon as we start inserting some additional priority relations, we are likely to get analogous worries. But it is an uncomfortable bullet to bite, because it undercuts many of the intuitive motivations for bottom-up views, such as that the Lego blocks are prior to the Lego sculpture.

A related point applies to top-down priority monistic views, at least assuming classical mereology. Maybe the Milky Way is prior to me, but it doesn’t seem right to say that the fusion of all people whose height in inches is even is prior to me (my height in inches is even). So the top-down priority monist seems to need a complicated story of when a whole is prior to its parts.

If we have highly restricted mereology, it becomes easier to say how the priority relation runs. If, say, van Inwagen is right and all we have are simples and organisms, then we can say that parts are always prior to wholes, and be done with it, as the only cases will be that simples are prior to cells and cells to multicellular organisms. Or we can reverse it and say that multicellural organisms are prior to their cells, cells are prior to their cells (while unaffiliated cells as well as unaffiliated simples are fundamental). In either case, the story is neat and simple.