Wednesday, November 3, 2021

Substantial change and simultaneous causation

Some philosophers hold that all fundamental instances of causal relations are simultaneous. Many of these philosophers are Aristotelians, though presentism provides a plausible route to this simultaneity doctrine independently of (other) Aristotelian considerations. I think the phenomenon of substantial change shows that this simultaneity doctrine is false.

When a horse changes into a carcass (or an electron-positron pair changes into a pair of photons) we have substantial change. Clearly, in such a case, the horse is the cause of the carcass.

Notice, however, that there is never a time at which both the horse and the carcass exists. This means that substantial change involves properly diachronic rather than simultaneous causation. And while there is a way of building a diachronic causal explanation out of simultaneous causation and persistence, I don’t see any way of doing that here. The trick in that way was to use the persistence of one or both of the relata of simultaneous causation to extend the relationship temporally. But here adding the earlier persistence of the horse or the later persistence of the carcass does not help, because it is still not the case that the horse and carcass have any moment of co-existence.

I think that this is where an Aristotelian will try to bring in matter. The horse has matter. When the horse perishes, its matter persists and comes to make up a carcass. We have a simultaneous relation between the horse and its matter, and then we have a simultaneous relation between the matter and the carcass.

But this doesn’t solve the problem. For the horse doesn’t just cause a heap of matter—it causes a carcass of a particular sort, made up of substances other than the substance of the horse. What persists in substantial change, on a classic Aristotelian view, is at most the prime matter. And the prime matter does not explain the form had by the carcass (or the parts of the carcass, if the carcass counts as a heap of substances).

We can even see the problem at the level of the accidents. Take the horse’s shape Sh and the carcass’s very similar shape Sc. Then, clearly, Sh causes Sc. One can see this empirically: if one rearranges the legs of the dying horse, the carcass’s shape changes correspondingly. But the only relevant thing that on the Aristotelian story persists across the change from horse to carcass is the matter: Sh does not persist, nor does anything that grounds Sh.

On reflection, the last line of thought shows that there could be a problem even for accidental change. For it seems likely to the case that a substance has an accident A which partially causes itself to be replaced by an accident B incompatible with itself. For instance, consider my current shape S1. In a moment, my body will shift into a new shape S2. The shape S1 partially causes the shape S2. Yet there is never a moment where I have both shapes. Indeed, at any time where I have shape S1, that’s the only shape I have. So, the shape S1 cannot cause any different future shape of me, assuming causation is always simultaneous.

This problem may be less serious than for substantial change, however, because one might say that S1 does not cause S2, but there is some deeper persisting accident that first causes me to have S1 and then causes me to have S2, so that there is no more a causal relationship between S1 and S2 than between a shadow of a moving person first appearing in one place and then in another. I think it is implausible to think that all cases where an accident A partially causes its immediate replacement by an accident B can be accounted by positing A and B to be mere epiphenomena, but I am not sure I have as good an argument against this as I do against the substantial change case.

I conclude from all this that while simultaneous causation is possible, it is not the case that all diachronic causation reduces to simultaneous causation.


Alexander R Pruss said...

One can solve the problem on a less classical Aristotelian view by supposing there are forms that persist across the substantial change.

Luiz Carlos said...

"Clearly, in such a case, the horse is the cause of the carcass." I object to this very strongly. Consider the following principle:

1. A is a fundamental efficient cause of B if and only if at some point in time A engages in some *positive* activity, or internal motion involving the possesion of some positive property, by means of which it brings about B.

This is incompatible, in general, with the horse being a fundamental cause of the carcass, because outside of special cases, such as the horse stabbing itself to death, the horse never engages in any positive activity which turns it into a carcass. The carcass results from the horse losing a positive property, namely its life, our soul, by means of some other, usually external, cause, and not due to any positive activity of the horse.

For example, if the horse's heart simply stops beating for whatever reason, the horse will die, but this death will be the result of merely the absence of activity and not of any positive activity the horse is engaged with.

If it is said that the horse causes the carcass by ceasing to beat its heart, which is a case of simultaneous causation, it also doesn't look ceasing to do something is a fundamental kind of causation, as it pressuposes doing it first and then ceasing to do it. So at any rate it would only happen in case some previous simultaneous causal relation obtained.

Alexander R Pruss said...

If the example doesn't work for you, consider a more positive transformation, such as when a sperm and egg produce a horse. As soon as the horse exists, the sperm and egg no longer exist.

Luiz Carlos said...

That is a fair point. In response I would say that this situation also seems to me akin to how a potter makes a pot (the canonical example of simultaneous causation). Suppose the potter's wife buys clay in the market for the potter to make a pot, then the wife is a simultaneous cause of the motions involved in buying clay, and gives the clay to the potter to make the pot. Because she contributed she can also be said to be a cause of the pot. Then that initial part of the work finishes and the potter takes the clay and makes the pot by continuously spinning it in the wheel. Both parts of the labor reduce to simultaneous causes, so the whole body of work consists of as a chain of simultaneous causes.

The sperm on the other hand is simultaneous with its own motion of getting to the egg (also we should assume external simultaneous causes are at play, since nothing can move solely through itself). The same applies for the motion of the egg itself. When they finally meet, all is prepared for conception to begin, hence an external cause (God) destroys both sperm and egg, takes their parts and reorders them into a new substance, which operates according to different principles. In this example the egg and sperm are related to the external cause both as the wife is related to the potter and also as the clay is related to the same potter (or at least the parts of the sperm and egg are so related).

The causal contribution of both sperm and egg only go so far as physically getting in place, since immediately when they get there they cease to exist. But it is not really the case that the horse begins to exist immediately after they cease to exist, it seems there needs to be some delay, for instance, between the time in which the sperm is ruptured and the time the genetic material finishes getting reorganized, and because the egg is also not the sole cause of this process, but it must depend on an external cause, it is really this external cause which is the more direct simultaneous cause of conception.

Alexander R Pruss said...

"hence an external cause (God) destroys both sperm and egg, takes their parts and reorders them into a new substance, which operates according to different principles": This sounds like occasionalism about horse reproduction to me.