“Suppose that we all come to believe C [(Consequentialism)]. (This will seem less implausible when we remember that C can be a pluralist theory, appealing to different moral principles.) We then decide that C is wholly self-effacing. We decide that it would make the outcome best if we caused ourselves to believe some improved version of Common-Sense Morality. We might succeed in bringing about this change in our beliefs. Given changes in the world, and in our technology, it might later come to be true that the outcome would be better if we revised our moral beliefs. But if we no longer believed C, because we now believed some version of Common-Sense Morality, we would not be led to make these needed revision in our morality.

But, in order to believe this morality, we must have forgotten that this is what we did. We would simply believe this morality. We might therefore not be led to revise our morality even if it came to be true that our belief in this morality would increase the chances of nuclear war.

These claims should affect our answer to the question whether it would make the outcome better if we all ceased to believe C. We might believe correctly that there is some other moral theory belief in which would, in the short run, make the outcome better. But once Consequentialism has effaced itself, and the cord is cut, the long-term consequences might be much worse.”

— Derek Parfit, Reasons and Persons (1984), pp. 41-42