Nor does he feel that there must be a true answer to all questions about personal identity. He feels that it is clearly absurd to consider the result of this operation, even if it is not survival in the strict identity sense, as complete death. In conclusion, Parfit does not at all reject the idea of the brain dividee surviving as two people, but rather the brain dividee having, in both post-operation bodies, the same identity as he did before. Parfit's theory, unlike the strict identity theory, does not regard loss of identity as a sufficient condition for 'not-survival'. Parfit's theory of descendant selves is clever, but the conclusions that lead up to its creation rely on three perhaps questionable assumptions.
Absolute symmetry is possible.
Changing the concept of identity is both allowable and preferable to changing the concept of a person. I will look at these assumptions in the order given, paying by far the most attention to the first. Naturally, Parfit's theories on this subject only hold water when they are within the comfortable framework of the psychological continuity theory. I would argue that it is. After all, Parfit agrees that the two connected halves of the brain in one body constitute one person.