which strong natural inclinations prompt us almost universally, and of which all the most obvious effects, commonly considered good, are effects upon the agent. We may then roughly distinguish ‘duties’ from expedient actions, as actions with regard to which there is a moral sentiment, which we are often tempted to omit, and of which the most obvious effects are effects upon others than the agent.
But it is to be noticed that none of these characteristics, by which a ‘duty’ is distinguished from an expedient action, gives us any reason to infer that the former class of actions are more useful than the latter—that they tend to produce a greater balance of good. Nor, when we ask the question, ‘Is this my duty?’ do we mean to ask whether the action in question has these characteristics: we are asking simply whether it will produce the best possible result on the whole. And if we asked this question with regard to expedient actions, we should quite as often have to answer it in the affirmative as when we ask it with regard to actions which have the three characteristics of ‘duties.’ It is true that when we ask the question, ‘Is this expedient?’ we are making a different question—namely, whether it will have certain kinds of effect, with regard to which we do not enquire whether they are good or not. Nevertheless, if it should be doubted in any particular case whether these effects were good, this doubt is understood as throwing doubt upon the action’s expediency: if we are required to prove an action’s expediency, we can only do so by asking precisely the same question by which we should prove it a duty—namely, ‘Has it the best possible effects on the whole?’
Accordingly the question whether an action is a duty or merely expedient, is one which has no bearing on the ethical question whether we ought to do it. In the sense in which either duty or expediency are taken as ultimate reasons for doing an action, they are taken in exactly the same sense: if I ask whether an action is really my duty or really expedient, the predicate of which I question the applicability to the action in question is precisely the same. In both cases I am asking, ‘Is this event the best on the whole that I can effect?’; and
