Williams argued that persons are different from most other kinds of things in this respect. Questions about their identity over time cannot have indeterminate answers.
The reason concerns just the phenomenon that Locke picked out: consciousness. Try thinking that it is indeterminate whether you will have some future person’s thoughts and experiences. Impossible, Williams says, therefore, it’s an all or nothing matter.
The branch-line case
How can we reconcile two thoughts?
- Being teletransported isn’t the same thing as dying.
- If we can teletransport someone to Mars, we can make multiple copies or leave the “original” intact.
Of course, you’re free to deny one or the other of these. Brittany denied #1. Barrett tried to do something similar.
But Parfit believes both, even though #2 seems to show that teletransportation isn’t a process that ensures I will be identical with any particular person.
Parfit’s answer? It’s a question. “How can a double success be a failure?”
More helpfully, he believes that being identical with a future person is not a necessary condition of surviving in the future. If they make two copies of me using the teletransporter, I will survive, but I will not be identical with either copy.
So, whose experiences will I have if they make two copies? Or, which one will I be? There’s no saying. The only thing we can do is describe what will happen, just as the only thing we can say about the table is which legs have been replaced. We can’t identify “the original.”
Where he’s going
Next time, we’ll see Parfit argue that if all a person consists of is material body and psychological connections, there is no way that identity questions could always have determinate answers.
So what if you buy Williams’s original point? Well, there is one other way for you to go. Maintain that we’re indivisible, immaterial souls!