David Lewis

One way for the utilitarian to deal with the Inquisitor is not to argue with him at all. You don’t argue with the sharks; you just put up nets to keep them away from the beaches. Likewise the Inquisitor, or any other utilitarian with dangerously wrong opinions about how to maximize utility, is simply a danger to be fended off. You organize and fight. You see to it that he cannot succeed in his plan to do harm in order—as he thinks and you do not—to maximize utility.

A second way is to fight first and argue afterward. When you fight, you change the circumstances that afford the premises of a utilitarian argument. First you win the fight, then you win the argument. If you can make sure that the Inquisitor will fail in his effort to suppress heresy, you give him a reason to stop trying. Though he thinks that successful persecution maximizes utility, he will certainly agree that failed attempts are nothing but useless harm.

David Lewis, ‘Mill and Milquetoast’, Australasian Journal of Philosophy, vol. 67, no. 2 (June, 1989), p. 159