The reason why actions are in a peculiar way revelatory of moral principles is that the function of moral principles is to guide conduct. The language of morals is one sort of prescriptive language. And this is what makes ethics worth studying: for the question ‘What shall I do?’ is one that we cannot for long evade; the problems of conduct, though sometimes less diverting than crossword puzzles, have to be solved in a way that crossword puzzles do not. We cannot wait to see the solution in the next issue, because on the solution of the problems depends on what happens in the next issue. Thus, in a world in which the problems of conduct become every day more complex and tormenting, there is a great need for an understanding of the language in which these problems are posed and answered. For confusion about our moral language leads, not merely to theoretical muddles, but to needless practical perplexities.