  This may already seem curious in two ways. First, one might suppose that language is rather our servant than our master, and that the rationality of reasoning in the ways he recommends needs to be established on general grounds, and not made to depend upon theses about the connotations of a word. Secondly, one of the theses in question—that practical “ought”s entail imperatives—is hardly obviously true; one might rather expect an Oxford philosopher, in the heyday of ordinary language philosophy, to be sensitive to the objection that the modal “You ought to do X” no more entails the imperative “Do X” than the modal “He ought to have got home by now” entails the indicative “He has got home by now”. (Think how much more plausible it is to infer the second from “He must have got home by now”.)