A reductive account of parthood in terms of causal powers

Analytic philosophers like to reduce. But not much work has been done on reduction of parthood. Here’s an attempt, no doubt a failure as most reductive accounts are. But it’s worth trying.

Suppose that necessarily everything has causal powers. Then we might be able to say:

1. x is a part of y if and only if every (token) causal power of x is a causal power of y.

Some consequences:

2. Transitivity

3. Reflexivity

4. If nothing other than x shares a token causal power with x, then x is mereologically simple and does not enter into composition. Plausibly nothing shares a token causal power with God, so it follows that God is mereologically simple and does not enter into composition.

How does this work for hard cases where parthood is controversial?

Suppose I lose a leg and get a shiny green prosthesis. If the prosthesis is a part of me, then the prosthesis’ power of reflecting green light is a power I have. It seems about as hard to figure out whether the power of reflecting green light is a power that I have as it is to figure out whether the prosthesis is a part of me. So here it is of little help.

Suppose I am plugged into a room-size heart-lung machine. Is the machine a part of me? Well, the machine has the power of crushing people by its weight. It seems intuitively right to say that by being plugged into that machine, I have not acquired the power of crushing people. So it seems that it’s not a part of me.

Is a fetus a part of the mother? Here, maybe the story is some help. The fetus eventually acquires certain powers of consciousness. These do not seem to be powers of the mother—she can be conscious while the fetus is awake. So, once consciousness is acquired, the fetus is not a part of the mother. But earlier, the fetus as the power to acquire these instances of consciousness, and the mother does not seem to, so earlier, too, the fetus does not seem to be a part of the mother. Here the story is of some help, maybe.

However, one doesn’t need all of (1) for some of the applications. The “only if” part of in (1) is sufficient for the heart-lung machine and pregnancy cases.

The greatest discovery in the history of human biology

If one searches for "the greatest discovery in the history of biology", the top hits indicate that it was the discovery of DNA. Maybe, though I'm not sure. But least in the history of human biology, the greatest discovery surely was the discovery that pregnancy is caused by coitus. (A discovery presumably made independently in multiple cultures.)

"Unexpected" and "unplanned" pregnancies

The process of conception is very chancy, with a randomly timed act of intercourse having a significantly less than one in ten probability of conception and with the conception probability peaking at around 1/2 for an act occurring at around ovulation. Any couple who knows these facts, absent some further information (such as a private revelation from God) cannot rationally expect a pregnancy to result from a sexual act, nor can the couple rationally be said to plan the pregnancy in a sexual act, for it is presumptuous to have something so chancy be one's plan. Thus, if a couple is rational and knows the probabilities, a pregnancy's resulting from a particular sexual act will always be an unexpected and non-planned consequence, though perhaps a hoped for and intended one.

However, the probability of conception for regular sexual activity over a longer period of time, say a year, is higher, and better than even. If something has a better than even probability, then it can be expected. Nonetheless, unless that probability is pretty high, say 9/10, which over the period of a year it is not, then it still is presumptuous to talk of the outcome as planned.

Thus, pregnancy is too chancy an event for it to be rationally planned, though of course it always can be planned for—even very low probability events can be rationally planned for. The standard loose distinction between planned/unplanned pregnancies, and to a lesser degree that between expected/unexpected pregnancies, can be replaced by a distinction between pregnancies hoped for and not hoped for, intended and not intended. (Note that "unhoped for" is not the same as "not hoped for". We use "unhoped for" in the case of events that are evaluated by the subject in a positive way, but a pregnancy need not so be. Likewise, Ryan Wasserman has argued that "not intended" is not the same as "unintended".) Of course, it may be that this is what people have all along meant by the words "planned", "unplanned", "expected" and "unexpected", but in a conceptually confused way. But in a matter as important as this, conceptual clarity is needed.