An ounce of prevention
In an earlier post, I mocked the movie Minority Report, whose character John Anderton says, “The fact that you prevented it from happening doesn’t change the fact that it was going to happen.” On the contrary, I said, the fact that it didn’t happen implies the fact that it wasn’t going to happen.
I speculated that Anderton might have meant to assert, “It would have happened if it hadn’t been prevented from happening.” But I said determinists must reject even that assertion. (I promise to explain why in future posts about counterfactual conditionals.) One consequence is that we must think and talk about prevention more carefully than we usually do.
When you discover that you left the ice cream out, you put it back in the freezer to keep it from melting. Your prospective reasoning, “If I don’t put it back, it will melt,” is consistent with determinism and backed by everything we know about ice cream. But determinism rejects the retrospective claim “If I hadn’t put it back, it would have melted” because in the counterfactual circumstances in which you don’t put it back, neither you nor the ice cream exist in the first place.
By putting the ice cream back, did you prevent it from melting? Yes, because ice cream left out at room temperature melts. But not because it would have melted if you hadn’t put it back.
