Suppose you are essentially an animal. If your cerebrum were transplanted into a vat and the rest of your body—including, of course, the brain-stem—were to maintain circulation, nutritive functioning, muscle tone and so on, where would you go? Would you go with the cerebrum in the vat, with the rest of the body, or would you be just plain dead?
Here’s a line of thought. There are more primitive animals that don’t have a cerebrum, but still have a circulatory system, a nutritive system, etc. Thinking about these animals makes on think that the survival of an animal has to do with maintenance of the lower level homeostatic functions. So, we go with the parts of the body responsible for such things.
But an Aristotelian animalist can resist the analogy to primitive animals on teleological grounds. For instance, our circulatory system’s physical resemblance to the circulatory systems of primitive animals misses out on a crucial metaphysical difference: our circulatory system has the support of the life of the mind as its central telos, and it supports the life of the mind by supporting the cerebrum. The teleological structure of primitive animals and human animals is different: functions that are close to the teleological center of the life of a primitive animal are further from the teleological center of human life. It may be the case that when an animal is divided, it goes with the parts that are teleologically more central. If so, then in the initial thought experiment, you would go with the cerebrum.
[By the way, this post represents a new workflow. I am using John MacFarlane pandoc, writing the post as a text file, and then running a script that does
pandoc -S filename | iconv -f utf-8 -t utf-16le | clip and pasting it in. This should make math less painful to type.]