The best question (Q5935794)

An angel offers to answer truthfully just one question; what should we ask her? A danger is that the angel's answer might fail to be informative, for reasons of self-reference and the semantic paradox, and \textit{T. Sider} [Analysis, Oxf. 57, 97-101 (1997; Zbl 0943.03583)] suggested asking ``What is (one of) the true proposition(s) that would be most beneficial for us to be told?''. The author suggests asking rather for all the true and beneficial propositions, limiting the length of the proposition and the vocabulary used, and asking the angel to rank the propositions by a more-beneficial-than ordering, made a total ordering \(<_R\) by length and alphabetical order; and then to give us only the first member from each equivalence class under our preferred logical theory. Varzi then points out that we need still to assume that the angel will answer in a Gricean-cooperative way.