Objective consequentialism is often criticized because it is impossible to know which of our actions will have the best consequences. Why exactly does this undermine objective consequentialism? I offer a new link between the claim that our knowledge of the future is limited and the rejection of objective consequentialism: that ‘ought’ implies ‘can’ and we cannot produce the best consequences available to us. I support this apparently paradoxical contention by way of an analogy. I cannot beat Karpov at chess in (...) spite of the fact that I can make each of many series of moves, at least one of which would beat him. I then respond to a series of objections. In the process I develop an account of the ‘can’ of ability. I conclude with some remarks about the bearing this attack has on subjective consequentialism. (shrink)