This is true, and Bernard Williams was a good writer for pointing this out. For example, Derek Parfit believes that to be a person is to instantiate some sort of abstract rational structure. As a consequences if they give me severe brain damage and also make a copy of me, the copy of me is me, and the person with brain damage is not me. Bernard Williams points out — this is crazy. To have my brain damaged is a bad thing happening to me. And it’s not lessened if there is a doppelganger somewhere calling himself Eric Kaplan. If anything that adds insult to injury.
Another example from Bernard Williams. A lot of philosophers say if you follow the rules you will never be a bad person. Your life could suck, but you won’t be bad. But Williams noticed the phenomenon of moral luck. Sometimes you might do something a little risky morally — eg leave your family to try to save the world — and it will work out. You will save the world! And then you’re a hero. But if you leave your family to save the world and fail — then you are just a creep.
Both of these cases have the same structure. You can solve a lot of tough phliosophical problems — in the first case — what is it to be a person over time? in the second — how can we act rightly — by just believing something that is…well the polite word is “implausible” but I am tempted to be less polite and call it “crazy” or “false”. Either, in the personal identity case, that to be me is to instantiate an abstract structure, or in the ethics case, that if I follow the rules I will never turn out to be a bad person.
I see three options:
1)Solve the problems and believe the crazy false thing. I don’t much like this one not just because the crazy false thing is false — I mean who knows what’s false? — but because the risk is so high. If, to take the personal identity case I am wrong that being me is being an abstract structure, I might allow myself to be brain damaged, and leave all my money to some doppelganger! If in the moral luck case I’m wrong that leading a good life means being immune to morally unlucky events, then I don’t protect myself, and I become awfully judgy.
2)Don’t believe the crazy false thing and just allow a lot of philosophical problems to remain unsolved. This is a good choice I think, though it can lead to a sort of defeatism which ain’t great.
3)Believe different crazy false things. This is attractive although risky. But if we are playing by the rules that it’s okay to believe ridiculously implausible things in order to have a nice-looking philosophical view, then why not explore the options?