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> Of course we don't even know whether this sense of self is really purely attached to the brain. That brain is still connected to the rest of your body, and who knows what the body chemistry of the body donor will do to the new brain?

Imagine just one aspect of this. A thyroid disorder.

If the donor body was hyperthyroid, the head transplant would result in someone with the symptoms of hyperthyroidism. Angry, irritable, racing pulse, etc. If they had hypothyroidism, they would be depressed, lethargic, etc.

And that's just one organ in the body. It could radically alter the "person" who they are presuming lives only in the head.

An even more striking example: putting a male brain in a female body or vice versa.

A good point, though for some people, that would be a better fit than what nature and chance gave them.

The separation of cojoined twins is potentially even more drastic, especially if it could be accomplished in those whose self-aware consciousnesses are not entirely independent.

Everyone's entire body, brain included, is undergoing continual change, simply from aging if not from injury or disease, and the changes that are most challenging to the concept of self are those that affect the brain.

I don't think emotions or feelings define identity. You could cut your leg off and be in immense pain, doesn't mean your identity changed.

The brain is still the same old brain just responding to changed input with appropriate output.

PTSD?

To take it further, imagine an even more futuristic procedure where a tumorous right brain is replaced alongside a healthy left brain. Who are you then?

Yep. Our whole legal system is built on the idea of one mind implanted in one body from birth. Things quickly start getting complicated when that breaks down.

To really cook your goose imagine if we could not only freely modify and "jump" between bodies, but also edit our memories. Kinda like Total Recall turned up to 110, where you can implant fake experiences, remove bad memories, take on an entirely new persona, or clone yourself and have a relationship with your clone. What really makes you "you" then?

There's a great little anime called Kaiba which explores exactly that: https://myanimelist.net/anime/3701/Kaiba

Altered Carbon sorta plays with this concept a lot. But it's set in a world were it is common place, and people have already detached identity from body.

It's commonplace in the Kaiba universe too, with "designer bodies", memory brokers and a black market of custom sex slaves etc.

So a murderer is he still a murderer if his memory is wiped? Or should we let him go?

Probably this came up in cases of amnesia already

You're right, this is an interesting question even without brain transplants. Are you guilty of a crime committed under hypnosis? What if you have multiple personality disorder? What if that disorder is the somehow cured or mitigated, so there's no risk of the murderous personality coming up again? It's a gateway to a marsh of awkward questions.