Of snakes and cerebra

Suppose that you very quickly crush the head of a very long stretched-out serpent. Specifically, suppose your crushing takes less time than it takes for light to travel to the snake’s tail.

Let t be a time just after the crushing of the head.

Now causal influences propagate at most at the speed of light or less, the crushing of the head is the cause of death, and at t there wasn’t yet time for the effects of the crushing to have propagated to the tip of the tail. Furthermore, assume an Aristotelian account of life where a living thing is everywhere joined with its form or soul and death is the separation of the form from the matter. Then at t, because the effects of crushing haven’t propagated to the tail, the tail is joined with the snake’s form, even though the head is crushed and hence presumably no longer a part of the snake. (Imagine the head being annihilated for greater clarity.)

Now as long as any matter is joined to the form, the critter is alive. It follows that at time t, the snake is alive despite lacking a head. The argument generalizes. If we crush everything but the snake’s tail, including crushing all the major organs of the snake, the snake is alive despite lacking all the major organs, and having but a tail (or part of a tail).

So what? Well, one of the most compelling arguments against animalism—the view that people are animals—is that:

1. People can survive as just a cerebrum (in a vat).

2. No animal can survive as just a cerebrum.

3. So, people are not animals.

But presumably the reason for thinking that an animal can’t survive as just a cerebrum is that a cerebrum makes an insufficient contribution to the animal functions. But the tail of a snake makes an even less significant contribution to the animal functions. Hence:

4. If a snake can survive as just a tail, a mammal can survive as just a cerebrum.

5. A snake can survive as just a tail.

6. So, a mammal can survive as just a cerebrum.

Objection: Only physical effects are limited to the speed of light in their propagation, and the separation of form from matter is not a physical effect, so that instantly when the head is crushed, the form leaves the snake, all at once at t.

Response: Let z be the spacetime location of the tip of the snake’s tail at t. According to the object, at z the form is no longer present. Now, given my assumption that crushing takes less time than it takes for light to travel to the snake’s tail, and that in one reference frame w is just after the crushing, there will also be a reference frame according to which z is before the crushing has even started. If at z the form is no longer present, then the form has left the tip of the tail before the crushing.

In other words, if we try to get out of the initial argument by supposing that loss of form proceeds faster than light, then we have to admit that in some reference frames, loss of form goes backwards in time. And that seems rather implausible.