If, then, we ask what rules are or would be useful to be observed in the society in which we live, it seems possible to prove a definite utility in most of those which are in general both recognised and practised. But a great part of ordinary moral exhortation and social discussion consists in the advocating of rules, which are _not_ generally practised; and with regard to these it seems very doubtful whether a case for their general utility can ever be conclusively made out. Such proposed rules commonly suffer from three main defects. In the first place, (1) the actions which they advocate are very commonly such as it is impossible for most individuals to perform by any volition. It is far too usual to find classed together with actions, which can be performed, if only they be willed, others, of which the possibility depends upon the possession of a peculiar disposition, which is given to few and cannot even be acquired. It may, no doubt, be useful to point out that those who have the necessary disposition should obey these rules; and it would, in many cases, be desirable that everybody should have this disposition. But it should be recognised that, when we regard a thing as a moral rule or law, we mean that it is one which _almost everybody can_ observe by an effort of volition, in that state of society to which the rule is supposed to apply. (2) Actions are often advocated, of which, though they themselves are possible, yet the proposed good effects are not possible, because the conditions necessary for their existence are not sufficiently general. A rule, of which the observance would produce good effects, if human nature were in other respects different from what it is, is advocated as if its general observance would produce the same effects now and at once. In fact, however, by the time that the conditions necessary to make its observance useful have arisen, it is quite as likely that other conditions, rendering its observance unnecessary or positively harmful, may also have arisen; and yet this state of things may be a better one than that in which the rule in question would have been useful. (3) There also occurs the case in which the usefulness of a rule depends upon conditions likely to change, or of which the change would be as easy and more desirable than the observance of the proposed rule. It may even happen that the general observance of the proposed rule would itself destroy the conditions upon which its utility depends.