Question: If you had a brainless body, and you donate half of your brain to that body, would you share the same consciousness as the person. More importantly, who is you?

Ian Cade answered on 12 Nov 2014:

(I should preface my post with the admission that no-one knows! and I really can’t say what happens, but I can offer some thoughts… anyway…)

I’m not in the habit of saying this all that frequently… but… Excellent question!

Why do I think so? Firstly you present a good thought experiment to probe the question… and because a surprising number of folk will simply brush away the question with “well consciousness is simply a product of the brain’s function and so (having done your surgery) you will just end up with two people that think they are ‘the original’ but with maybe half the memories, only half functional bodies etc”

But is this reasonable?

Consciousness does seem to be connected with the brain, ‘remove the brain and the person stops being conscious’ but as you suggest what if you remove just some? There are stroke patients and people who have other brain injuries that seem to retain their consciousness (albeit with reduced functionality, partial paralysis and the like). And it seems there is no one area of brain that is where consciousness lives, so does consciousness just slosh around the brain filling up the available space? if so what could it be made of?

The other problem with saying “consciousness is just a product of the brain” is that the brain has another obvious function that can confuse the issue, namely, controlling the body. The problem is this: the only way you can probe whether someone ‘feels’ conscious is by asking them. If you remove a part of their brain might you might affect their ability to answer. It doesn’t seem possible to decide whether that bit of brain you have removed had a direct causal relationship to the consciousness of the person, or whether it was just associated with their ability to answer.

In essence probing ‘what consciousness is’ is not amenable to scientific study since there is no way of setting up an experiment where you can directly measure the sensation of being conscious (Simply measuring brain waves/activity is not the same thing. There may be correlations between particular conscious states and brain activity, *but* correlation does not (always) equal causation!)

So, what do we know about consciousness (by which I meant the sensation of existing not the simple problem of deciding whether someone is asleep or not). Essentially not very much… Firstly, you can only really be sure that you, personally, are conscious. It is after always possible that everyone around you is just an automaton or zombie or whatever… and… hmmm… that’s about all really (from a scientific perspective).

… not very satisfactory I agree… but it does mean there is a lot to discover!

Another thought experiment on this subject is to try to imagine making a copy of yourself and imagining what the copy might ‘feel’. Start with maybe a crude ‘copy’ – a stick figure on a piece of paper… does it ‘feel’ anything (probably not, but since it can’t communicate I can’t say for sure)… maybe a slightly better copy could work – try a proper sketch… etc. etc. etc. Do you ever get to a point when the copy ‘feels’ the same as you?