Accidents and parts

Aristotelian ontologies are committed to substances and their accidents.

But what about proper integral parts, like arms and legs?

These are typically not taken to be substances, because substances are not supposed to be parts of other substances. They seem to be a puzzling third category of things.

One set of puzzles comes from the connection between integral parts and accidents of the whole. For instance, the specific shape of a substance is usually considered an accident. But now imagine that I lose a leg and nothing else. Since I’ve lost nothing else, I haven’t lost my specific accident of shape, and hence, oddly, I have only one leg, but I have the same shape as before.

This is not quite as absurd as it may seem. After all, I could have the same shape I do and only one leg. I could, for instance, have one leg and a giant swelling shaped exactly like another leg. Still, there is something rather strange about the fact that mere loss of a leg causes the growth of a leg-shaped swelling.

Another set of puzzles comes from the accidents of the parts. A leg has its own shape, which is not a shape of the whole. Thus it seems that some accidents are not accidents of substances. This is a bit easier to handle. For we might say that a leg’s shape is an accident of the whole. However, the leg’s shape is not (as would be absurd) an accident of the whole being leg-shaped but an accident of the whole having a leg shaped thus-and-so. Thus, the specific shape accident of the leg makes the leg have that shape and makes the whole be legged in that shape.

Furthermore, suppose the leg changes its shape accident. How does that result in the whole automatically changing its shape accident to match? Or, conversely, how is it that when the whole is reshaped, so are the parts?

Much of the difficulty can be averted by denying that there are shape, size, mass, and other similar accidents of the whole. Instead, global shape, size, mass and similar facts about the whole are grounded in accidents of parts: shape, size, mass and location-in-the-whole accidents of the parts. This is a significant modification from traditional Aristotelianism, but perhaps it is the right move. Then if you remove an integral part, you remove all of its accidents, and the whole changes in the shape, size, mass, etc. that the part’s accidents helped ground.

This does not, however, solve the problem of having to posit a third category—proper integral parts—on top of substances and their accidents. I like the thought of solving this problem by identifying integral parts with special kinds of accidents—the heart with heartedness, etc.