– A memory theorist of personal identity would need an account of how person could have amnesia, degenerative Alzheimer’s, total memory loss from brain damage, etc. How could we treat a person for memory loss? Say something goes wrong in the limbic system and makes it impossible for some person to remember. I invent some artificial limbic system part. I it possible for me to implant in on a person? Perhaps we say that the identity of that person bootstraps on my own identity. The patient participates in the memory of his family members who bring him to the clinic, or the doctor who treats him. But then we get the fascinating but probably incoherent concept of a “person by participation” or “person not of himself”.
-Say we want to distinguish ontological identity (being an individual) from verificational identity (knowing that one is an individual). What to do with the problem that personal identity seems to be largely self-reflection? The first person act of knowing enters into the ontology. So do we evade the problem of confounding ontology and epistemology, or become trapped in it?
Suppose that subject A is suffering from a disease that causes cerebral neurons to die off, one by one. An ingenious treatment is applied: as each neuron dies, it is replaced by a small 2-way radio modem, connecting to a neuron-simulating program dwelling on the cloud (i.e., realized by different combinations of hardware fixtures at different points in time). Eventually, A’s entire cerebrum has been replaced by such modems, with the result that all of A’s cerebral processing is being handled by the simulation program on the web.
Now, here’s where it gets interesting. There are a large number of subjects suffering from the same condition.
Another approach to the experiment would be to replace the neurons with prosthetics: assume a world of perfectly advanced prosthetics, like the Star Wars universe. Now let a Jedi become progressively more and more beaten in battles: first he looses a hand, then an arm, a leg, digestive tract, etc. Or, less dramatically, let him have a progressive disease that requires more and more of his organs and tissues to be replaced by prosthetics. The problem is that there is a limit to this replacement: a prosthetic is essentially an imput-output device: you need to hook it up to something. A completely prosthetic organism is either a contradiction, or a being that could not do anything. It would be a prosthetic not hooked up to anything, which wouldn’t do anything more than a prosthetic on the shelf.
But where does this leave us? It is an obvious objection to considering organs as tools, but it’s unclear what other option we have. “Organ” is just the stem of the Greek word for “tool”. By the same token, it seems to argue that identity cannot be the property of any input-output system.
– We want the physical to be close enough to the scientific to always be symmetrical, i.e. just as open to going in the reverse direction to the way it goes. But the chemical processes underlying life, as life, cannot be characterized in this way. Life and death or sickness and health are not the same sort of things as freezing and thawing, oxidation and reduction. The difference doesn’t require philosophy either, but is built into the science: oxidation and reduction are dealt with indifferently by physics, and as simply two halves of what one is studying; but the living and the dead are not two halves of what biology studies. Likewise, sickness and health are not two indifferent halves of medicine or anatomy. The anatomy book does not show the amputated, tumor-having, etc.
-If by “identity” we mean a whole (complete entity) that acts for itself as a whole, then there is no such thing as natural or physical identity. The best a natural whole can do is to have one part move another part. This is simply a lemma to the First Way, one which happens to prove that God alone has personal identity, at least as described in the opening sentence. As a further lemma to this, divine simplicity is not God as property-identical so much as God being the only being that actually acts entirely for himself: i.e. an entity that acts entirely as the entity he is. What we imagine is true of all identity is in fact verified only in the divine instance of it.