Personal Identity

 One of the topics I've always stayed away from is the topic of personal identity - this is a notoriously difficult thing to talk about: what makes you you? This question has been haunting me for quite some time so I decided to finally take it head on and see what I can come up with, if anything.

The premise that I'm going to work with is the idea that the only thing that gives us our personal identity is the current configuration of our brains - the way the neurons are interconnected and the information in this network is how our personal identity emerges - no soul or "magic substance" behind all of this. Of course, this is pretty much the established view in the scientific community, although there are exceptions. So the question is - what can we say about the personal identity starting from this premise? What are the implications? Can you be cloned? Copied? Re-instantiated? Is the copy of yourself also you?

Imagine the following scenario: Alice is a murderer. She is caught by the police and convicted to 20 years in prison. However, before she is sent to prison, Alice dies. Alice happens to be part of this very advanced society who can create identical copies of a person, basically re-instantiating Alice - so they do exactly that: a "new" Alice with all her memories, all her neural connections etc. They convict this Alice to 20 years in prison for murder. According to our premise, it's the same Alice, so this should not be a problem, right? What is the difference, exactly, between the "original" Alice that committed the murder and this newly-created Alice that has the same brain structure and memories (and everything) as the original one?

If you think this is fine, consider the next scenario: Bob also lives in this advanced society able to create identical copies of people. Bob is also a murderer. Bob is caught by the police as well and is sentenced to 20 years in prison. However, knowing about Alice's case, Bob proposes something to the authorities: "how about we create an identical copy of me that is going to serve the sentence?", says Bob. Since an identical copy of Bob is Bob, the authorities agree. Bob's copy goes to prison while the original Bob is free to roam around killing people. For each new murder Bob comes up with the same solution: a new copy that is going to serve time on his behalf. The prison fills up with copies of Bob, all identical, while the original Bob is free to do as he pleases, with no consequences.

The question is - what became of the idea that it's just the brain structure that matters in determining you? Is any continuity in spacetime important? If I teleport you from one place to another and destroy the original copy and re-instantiate a new, identical one on the Moon - is it the same you?

First, let me present a case by VS Ramachandran - split brain patients:

As you can see above, if you cut the corpus callosum in the human brain, the nerve bundle that connects the left and right brain hemispheres, you don't cut someone's consciousness in half. Instead there are now two consciousnesses inside the brain - one for the left hemisphere and another for the right hemisphere. Each of these would say that they are you (only the left hemisphere can talk, but the right hemisphere can grunt or sing). So I think the right way to see our personal identities is as a story of the brain, when the brain is healthy. For split brain patients there are two stories, one for each hemisphere.

Since only the left hemisphere can talk (and can also move the right hand), suppose as this individual (is "individual" still the right word for a human being that has two consciousnesses?) goes around and punches, with the right hand, someone else. Maybe he also insults the person. Is the right hemisphere, who is also him, responsible for what the left hemisphere did? After all, only the left hemisphere can insult since it's the only hemisphere that can talk. Also, the punch happened with the right hand, controlled by the left hemisphere.

Now let's think more carefully about what exactly happens when we create a copy of someone. Say we take Bob and create a copy of him. Are they really identical? Well, first of all, they are at different locations in spacetime: Bob is here and Bob's copy is there. As soon as we create Bob's copy, they will be separate persons, even if we create them exactly identical. Why? Because they are located in a different place relative to the environment. I think when discussing things like personal identity people lose track of the importance of the environment - people concentrate only on the individual being copied. But the environment matters: Bob being located here takes a particular set of inputs: photons hitting his skin, his eyes, different pressure by the air molecules hitting his skin, the way the bed sheet feels like where he's laying down, sound waves reaching his ears and so on. Bob's copy, over there, also has a particular set of inputs from the environment, different ones than Bob since he's located somewhere else.

Therefore, considering the fact that they get different inputs which then become nerve impulses in their nervous system and modify the already existing synapses, synaptic weights, flow of ions and so on - they are not identical anymore - Bob and Bob's copy are not identical, as soon as Bob's copy has been created - they are separate individuals.

But let's push this copying thing to the extreme. Suppose you truly want an identical copy to happen. You take Bob and put him in empty space, in a vacuum chamber (suppose he could survive that environment). In this vacuum chamber you also create Bob's copy. They are both asleep and they are in the same environment - they are indeed in a separate location of spacetime, Bob here and Bob's copy there, but the environment is exactly the same: no noise, same temperature (pretty much zero Kelvin), no photons traveling to them other than the black body radiation etc. Next, suppose you're the original Bob and you wake up. What credence should you assign to the fact that you're the original one and not the copy? I would say 50% - you truly don't know if you're the original one or the copy since both have the same memories. Now suppose this room has an even crazier contraption: a device that, in the darkness of the room and using quantum processes, is moving Bob and his copy around in space such that not even the experimenters themselves know which is Bob and which is his copy. Remember, the room is completely dark so nobody knows, after Bob and his copy were moved around, which is which.

I think you would agree that in this situation not only does the objective world not know which is Bob and which is his copy, but they themselves don't know which is which. Seems like a perfect situation for our push towards what exactly personal identity is.

Now let's say that Bob and his copy wake up in this room (and somehow survive in that environment) having exactly the same brain state, synapses, environmental feedback (none) and so on. They are identical. The experimenters need to execute one of them - either Bob or his copy. Should it matter which one? I would say that from an objective perspective, from the experimenters' point of view there would be no difference. But now let's look at the subjective part - each of the two would be terrified and would prefer the other to die. Why? Because they are important to themselves. You are the story of what that particular neural network is creating. Bob is the consequence of his neural network's activity and Bob's copy is the consequence of Bob's copy neural network's activity. This is simply an inescapable fact.

Regardless of anything else - you are here, a process in this neural network. You cannot be anywhere else. Even if I create an identical copy somewhere else, the process that is happening in your brain, here, is still going on - you see through the same eyes, hear with the same ears etc - this story of this network is here. What matters is that for each story created by each neural network, they are important to themselves.

But now let's consider this situation: you put Bob into the dark room where environment plays no role. You copy Bob's entire information and you destroy Bob, say you throw him into a black hole as he's sleeping. You wait 5 minutes and, using Bob's copied information, you re-materialize Bob exactly as he was 5 minutes ago and you wake him up. Is he still Bob? Is the same subjective experience there, the same him?

I don't know. Common sense would say that if it walks like a duck and quacks like a duck it is a duck. Bob is Bob - looks like him, acts like him, has the same information as him, the same memories - it should be Bob. He even says it's him.

I think, in the end, there is no way to know. We still haven't defined exactly what does it mean to be me. If it means having the same information, acting the same, reporting the same etc then objectively it's me. Subjectively? If subjectivity is given by the physical mechanisms in the brain then it's me also subjectively - but then you bump into the problems mentioned above. I think in real life the environment needs to be taken seriously - that will probably make the difference. It could also be that, simply because we're bumping into some weird paradoxes, that should clue us into the fact that such things are not practically possible - the universe doesn't allow them to happen. It could be that we simply can't identically copy information, including brain configurations, due to quantum mechanical limitations: the Heisenberg uncertainty principle, the no cloning theorem and so on. You simply can't know the full quantum state of a system such that you truly create an identical copy of that system, including if the system is Bob. Therefore you can't have an identical copy of Bob and all of this mental gymnastics goes away - there will be just one Bob and one Bob only - the imperfect copies will be their own personal identities, their own selves, with some small differences here and there. The question is if any of these quantum effects play a role in determining personal identity or not - I don't know.

Another possibility is that personal identity doesn't really exist - it's a carefully constructed story by the neural network that we call the brain, a careful stiching of separate agents that looks like a unified individual - it's not. After all, we've seen in the split brain patient situation that as soon as you cut the corpus callosum what looked like a unified self becomes two selves. There are other pathologies where there are 20 selves - they can even be in the same dream and talk to each other, as some people report. So personal identity might be an illusion and there's no potential answer to this question, it's a futile attempt to solve it. Again, the personal identity and subjectivity that you experience now is a story that the neural network that is connected to your eyes, skin, ears, guts and so on is producing, and any identical copy of you will have its own eyes, skin, ears, guts - a different experience.

I would leave one door open for a reinstantiation of yourself, assuming personal identity actually exists - you are a product of the universe. After you die, just by chance, it could be that your exact pattern, the same that you have now, will be re-instantiated. If personal identity exists, it will be the same you as the you now - you would be immortal. If the universe is cyclical and the brain configuration/information is all that is needed for our current experience then we are all truly immortal.

In the end, I can tell you this: no matter how long I think about this I find no way to truly solve this problem - depending on how I think sometimes it looks like a copy is you, sometimes it doesn't, sometimes personal identity seems so real, sometimes it looks like a total fabrication - I truly don't know. But it's still fun to go through some possibilities and think of the ethical implications, depending on how you view the issue of personal identity, and wrestle with yourself (see, can't get rid of yourself, can you?) in trying to solve these.