Thursday, November 17, 2022

Cerebrums and rattles

Animalists think humans are animals. Suppose I am an animalist and I think that I go with my cerebrum in cerebrum-transplant cases. That may seem weird. But suppose we make an equal opportunity claim here: all animals that have cerebra go with their cerebra. If your dog Rover’s cerebrum is transplanted into a robotic body, then the cerebrumless thing is not Rover. Rather, Rover inhabits a robotic body or that body comes to be a part of Rover, depending on views about prostheses. And the same is true for any animal that has a cerebrum.

It initially seems weird to say that some animals can survive reduced to a cerebrum and others cannot. But it’s not that weird when we add that the ones that can’t survive reduced to a cerebrum are animals that don’t have a cerebrum.

The person who thinks survival reduced to a cerebrum is implausible for an animal might, however, say that this is what’s odd about it. An animal reduced to cerebrum lacks internal life support organs (heart, lungs, etc.) It is odd to think that some animals can survive without internal life support and others cannot.

But compare this: Some animals can partly exist in spatial locations where they have no living cells, and others cannot. The outer parts of my hairs are parts of me, but there are no living cells there. If my hair is in a room, then I am partly in that room, even if no living cells of mine are in the room. But on the other hand, there are some animals (at least the unicellular ones, but maybe also some soft invertebrates) that can only exist where they have a living cell.

One might object that the spatial case and the temporal case are different, because in the spatial case we are talking of partial presence and in the temporal case of full presence. But a four-dimensionalist will disagree. To exist at a time is to be partly present at that time. So to a four-dimensionalist the analogy is pretty strict.

Finally, compare this. Suppose Snaky a rattlesnake stretched along a line in space. Now suppose we simultaneously annihilate everything in Snaky. Now, “simultaneously” is presumably defined with respect to some reference frame F1. Let z be a point in Snaky’s rattle located just prior (according to F1) to Snaky’s destruction. Then Snaky is partly present at z. But with a bit of thought, we can see that there is another reference frame F2 where the only parts of Snaky simultaneous with z are parts of the rattle: all the non-rattle parts of Snaky have already been annihilated at F2, but the rattle has not. Then in F2 the following is true: there is a time at which Snaky exists but nothing outside of Snaky’s rattle exists. Hence Snaky can exist as just a rattle, albeit for a very, very short period of time.

Hence even a snake can exist without its life-support organs, but only for a short period of time.

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