whether the event in question be some effect upon what is mine (as it usually is, where we talk of expediency) or some other event (as is usual, where we talk of duty), this distinction has no more relevance to my answer than the distinction between two different effects on me or two different effects on others. The true distinction between duties and expedient actions is not that the former are actions which it is in any sense more useful or obligatory or better to perform, but that they are actions which it is more useful to praise and to enforce by sanctions, since they are actions which there is a temptation to omit.
102. With regard to ‘interested’ actions, the case is somewhat different. When we ask the question, ‘Is this really to my interest?’ we appear to be asking exclusively whether its effects upon me are the best possible; and it may well happen that what will effect me in the manner, which is really the best possible, will not produce the best possible results on the whole. Accordingly my true interest may be different from the course which is really expedient and dutiful. To assert that an action is ‘to my interest,’ is, indeed, as was pointed out in Chap. III. (§§ 59—61), to assert that its effects are really good. ‘My own good’ only denotes some event affecting me, which is good absolutely and objectively; it is the thing, and not its goodness, which is mine; everything must be either ‘a part of universal good’ or else not good at all; there is no third alternative conception ‘good for me.’ But ‘my interest,’ though it must be something truly good, is only one among possible good effects; and hence, by effecting it, though we shall be doing some good, we may be doing less good on the whole, than if we had acted otherwise. Self-sacrifice may be a real duty; just as the sacrifice of any single good, whether affecting ourselves or others, may be necessary in order to obtain a better total result. Hence the fact that an action is really to my interest, can never be a sufficient reason for doing it: by shewing that it is not a means to the best possible, we do not shew that it is not to my interest, as we do shew that it is not expedient. Nevertheless there is no necessary conflict between duty and interest: what is to my interest may also be a means to the best possible.
