Parfit argues that no view of personal identity can meet the following two requirements (p. 267):
Parfit thinks that if there is such a thing as personal identity, and if it does have great importance, then some view must be able to meet both of (1) and (2). The problem is that, he argues, no view does.
Recall that we have adopted reductionism for purposes of argument. Then we have two plausible views of personal identity: (various versions of) the psychological theory, and (various versions of) the physical body theory. Parfit thinks that he can show that neither of these can meet both of (1) and (2) via two kinds of arguments.
Consider first the psychological view. Any defended of that view, when confronted with the psychological spectrum, will have to find some percentage of memory change which suffices to destroy personal identity. But then the personal identity can depend on a relatively trivial fact – e.g., the destruction of a single memory. And this violates (2).
An analogous argument holds against a defender of the physical body view. Personal identity will depend on a relatively trivial fact — e.g., the destruction of a single cell of one’s body. And this again violates (2).
The same argument can be run against a ‘combination’ view, which makes use of facts about both bodily and psychological continuity, using the combined spectrum.
Another class of cases which seem to count against any view satisfying (1) and (2) are cases of ‘division’.
Against the psychological view: the Branch-Line Teletransporter case. How could the psychological view be revised? How about the following
Does this solve the problem posed by the Branch Line?
Against the physical body view: cases of bodily fission. How could the physical view be revised? How about the following:
Do these do any better with respect to requirements (1) and (2)? Could either of (1) or (2) be called into question?
Parfit thinks that we should say that what does matter is psychological continuity. As the case of the Branch Line Teleporter shows, psychological continuity is not identity. But that just means that we should give up no caring about personal identity. Whether it is me that survives teleportation doesn’t really matter; what matters is whether there is someone psychologically continuous with me.
Parfit thinks that this discovery is liberating:
“Is the truth depressing? Some may find it so. But I find it liberating, and consoling. When I believed that my existence was a further fact, I seemed imprisoned in myself. My life seemed like a glass tunnel, through which I was moving faster every year, and at the end of which there was darkness. When I changed my view, the walls of my glass tunnel disappeared. I now live in the open air. There is still a difference between my life and the lives of other people. But the difference is less. I am less concerned about the rest of my own life, and more concerned about the lives of others.
When I believed [that personal identity was a further fact of importance] I also cared more about my inevitable death. After my death, there will be no one living who will be me. I can now redescribe this fact. Though there will later be many experiences, none of these experiences will be connected to my present experiences by chains of such direct connections as those involved in experience-memory...There will later be memories about my life. ...My death will break the more direct relations between my present experiences and future experiences, but it will not break various other relations. This is all there is to the fact that there will be no one living who will be me. Now that I have seen this, my death seems to me less bad..” (281)
What do you think?