The paradox of the question
Since A4 is obviously useless, Markosian asks what has gone wrong.2 Responding to Markosian, Sider (1997) points out that the angel has given the wrong answer to Q4. Were A4 correct, then Q4 would be the best question to have asked and A4 its answer; but since there are better question/answer pairs than (Q4, A4), A4 cannot be the correct answer to Q4. Sider goes on to argue that Q4 cannot be the best question: suppose the answer to Q4 is X, then X consists in just the (useless) ordered pair (Q4, X).3 It seems that for any answer the angel gives of the form X = (Q4, X), such as A4, the angel undermines the answer it gives. However, not every answer of this form need be trivial. For instance, if we write Y for the solution to the problem of world hunger, another answer to Q4 would be