Imagine that you suffer a tragic accident that leaves you lying brain-dead on a hospital bed. Your body is still alive but you are no longer self-conscious, nor ever can be.
Are you still you?
Some thinkers have argued that a person at a time A is the same as a person at a time B because his body or brain is the same body or brain at both times, in the sense that they are continuous in space and time. Other have argued that this is not the case, and that a person at a time A is the same as a person at a time B because they are psychologically continuous; that is, the mental states of the person at a time B derive or descend from the mental states of the person at a time A.

To help resolve this problem, the philosopher Sydney Shoemaker asks us to imagine that science has advanced to such an extent that brain transplants are now possible. Two men, Brown and Robinson, have their brains removed and exchanged. One of these men dies, but the other, say the one with Brown’s body and Robinson’s brain (let’s call him ‘Brownson’), regains consciousness. Who is this man Brownson? When asked his name he replies ‘Brown’. He does not recognize Robinson’s wife, but welcomes Brown’s wife and family as his own and is privy to all of Brown’s most intimate childhood memories.

Most people would argue that Brownson is Brown, or much more Brown than Robinson, indicating that a person is not reducible to his or her body. This leaves us with two possibilities: either Brownson is Brown because he has Brown’s brain, or he is Brown because he is psychologically continuous with Brown.

Many people have survived with half their brain destroyed. So let’s imagine that Brownson’s brain (or anyone’s brain, say, Smith’s) is now divided into two equal halves, and that each half is transplanted into a brainless body. After the operation, two people awake who are both psychologically continuous with Smith, and who have the same personality, relations, and memories as Smith. If both people are psychologically continuous with Smith, are they both Smith? Most people would argue that, although they are very similar, they are in fact two different people and, over time, will become increasingly different, if perhaps only subtly.
In conclusion, It seems that what makes you a person depends causally upon the existence of your brain but at the same time amounts to something more than just your brain. What this might be is unclear, and perhaps for a reason. We have a tendency to think of our personhood as something concrete and tangible, something that exists ‘out there’ in the real world and extends through space and time. But it is possible that personhood is in fact nothing more than a product of our minds, merely a convenient concept or schema that enables us to relate our present self with our past, future, and possible selves.

According to the Buddha, the failure to recognize this illusion of the self is the source of all ignorance and unhappiness. It is by renouncing the self—that is, by dropping his ego defences and committing symbolic suicide—that a person can open up to different modes of being and relating and become a pure essence of humanity. Only then is he free to recast himself as a more mindful, joyful, and productive person, and, in so doing, attain the only species of transcendence and immortality that is open to man.
Neel Burton is author of Hide and Seek: The Psychology of Self-Deception, Heaven and Hell: The Psychology of the Emotions, The Art of Failure: