One answer might go like this: “But I don’t think that. If I use W to denote the proposition that I have free will, I can think of no experiments whose results might provide evidence for or against W. I don’t assign a high subjective probability to (W|). For any other proposition Y, I don’t see any difference between the probability of (Y|W) compared to (Y|~W)”.
“Nevertheless I choose to assume W because I often find it easier to estimate P(Y|W) than to directly estimate P(Y), especially when I can influence P(Y) by an act of ‘will’.”
A belief doesn’t have to be useful to be valid; an assumption doesn’t have to be true to be useful.
“Why do I think I have free will?”
One answer might go like this: “But I don’t think that. If I use W to denote the proposition that I have free will, I can think of no experiments whose results might provide evidence for or against W. I don’t assign a high subjective probability to (W|). For any other proposition Y, I don’t see any difference between the probability of (Y|W) compared to (Y|~W)”.
“Nevertheless I choose to assume W because I often find it easier to estimate P(Y|W) than to directly estimate P(Y), especially when I can influence P(Y) by an act of ‘will’.”
A belief doesn’t have to be useful to be valid; an assumption doesn’t have to be true to be useful.