Suppose a woman crushes the head of a very long serpent. If the snake all dies instantly when its head is crushed, then in some reference frame the tail of the snake dies before the woman crushes the head, which seems wrong. So it seems we should not say the snake dies instantly.
I am not talking about the fact that the tail can still wiggle a significant amount of time after the head is crushed, or so I assume. That’s not life. What makes a snake be alive is having a snake substantial form. Death is the departure of the form. If the tail of the headless snake wiggles, that’s just a chunk of matter wiggling without a snake form.
What’s going on? Presumably it’s that metaphysical death—the separation of form from body—propagates from the crushed head to the rest of the snake, and it propagates at most at the speed of light. After all, the separation is a genuine causal process, and we are supposed to think that genuine causal processes happen at the speed of light or less.
So we get a constraint: a part of the snake cannot be dead before light emitted from the head-crushing event could reach the part. But it is also plausible that as soon as the light can reach the part, the part is dead. For a headless snake is dead, and as soon as the light from the head-crushing event can reach a part, the head-crushing event is in the absolute past of the part, and so the part is a part of a headless snake in every reference frame. Thus the part is dead.
So death propagates to the snake exactly at the speed of light from the head-crushing, it seems. Moreover, it does this not along the snake but in the shortest distance—that’s what the argument of the previous paragraph suggests. That means that a snake that’s tightly coiled into a ball dies faster than one that is stretched out when the head is crushed. Moreover, if you have a snake that is rolled into the shape of the letter C, and the head is crushed, the tail dies before the middle of the snake dies. That’s counterintuitive, but we shouldn’t expect reality to always be intuitive.
2 comments:
1. Why say that the separation of form from body is a physical process? Forms are physical, and their relation to the body is, well, that of a formal cause and not that of an efficient cause (when Aristotle and Aquinas say that the form is an efficient cause, they don't mean that the form as instantiated in the body is an efficient cause of its own informing). Aquinas says of bodily forms (ST III.90.3) that the "nature of which is that the whole is not present in each of the parts, either as to its entire power, or as to its entire essence, but that it is present to all of them together at the same time." Why not simply say that if the body isn't of the right sort to be informed by that kind of form (in its own proper frame), eg because the head was crushed, that the form departs at once?
2. If the form's departure is a physical process, then of course it's bounded by the speed of light, but why should it occur at the speed of light, and particularly why should it follow the light cone structure? Light transmission in optical fiber is physical, but it proceeds at the speed of light in glass not that in vacuum, and it proceeds along the fiber even when it's coiled. If the brain death is the physical cause of the tail death, why not say that it proceeds at the speed and pathways of the brain's causal relationships with the tail, precisely those causal relationships that bound them into one life to begin with?
Ryan:
Ad (1): When you say "departs at once", in what reference frame is the "at once" understood? Simultaneity is apparently relative.
Ad (2): I used to be inclined to think it should follow the length of the snake. But this has the consequence that there are reference frames in which you have a living headless snake--reference frames in which the form is separated from the head but not yet from the rest of the body. That is counterintuitive.
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