=92.= A difficulty in distinguishing this task, which Ethics may perhaps undertake with some hope of success, from the hopeless task of finding duties, arises from an ambiguity in the use of the term ‘possible.’ An action may, in one perfectly legitimate sense, be said to be ‘impossible’ solely because the idea of doing it does not occur to us. In this sense, then, the alternatives which do actually occur to a man would be the only _possible_ alternatives; and the best of these would be the best possible action under the circumstances, and hence would conform to our definition of ‘duty.’ But when we talk of the best _possible_ action as our duty, we mean by the term any action which no _other_ known circumstance would prevent, _provided_ the idea of it occurred to us. And this use of the term is in accordance with popular usage. For we admit that a man may fail to do his duty, through neglecting to think of what he _might_ have done. Since, therefore, we say that he _might_ have done, what nevertheless did not occur to him, it is plain that we do not limit his _possible_ actions to those of which he thinks. It might be urged, with more plausibility, that we mean by a man’s duty only the best of those actions of which he _might_ have thought. And it is true that we do not blame any man very severely for omitting an action of which, as we say, ‘he could not be expected to think.’ But even here it is plain that we recognise a distinction between what he might have done and what he might have thought of doing: we regard it as a pity that he did not do otherwise. And ‘duty’ is certainly used in such a sense, that it would be a contradiction in terms to say it was a pity that a man did his duty.