What is objectively right, then, is in some way dependent on consequences. The most natural supposition to start from would be that the objectively right act, under any circumstances, is the one which will have the best consequences. We will define this as the most fortunate act. The most fortunate act, then, is the one which will produce the greatest excess of good over evil, or the least excess of evil over good (for there may be situations in which every possible act will have consequences that are on the whole bad). But we cannot maintain that the most fortunate act is always the one which is objectively right, in the sense that it is what a wise man will hold that he ought to do. For it may happen that the act which will in fact prove the most fortunate is likely, according to all the evidence at our disposal, to be less fortunate than some other. In such a case, it will be, at least in one sense, objectively wrong to go against the evidence, in spite of the actual good result of our doing so. There have certainly been some men who have done so much harm that it would have been fortunate for the world if their nurses had killed them in infancy. But if their nurses had done so their action would not have been objectively right, beause the probability was that it would not have the best effects. Hene it would seem we must take account of probability in judging of objective rightness; let us then consider whether we can say that the objectively right act is the one which will probably be most fortunate. I shall define this as the wisest act. (§ 16 ¶ 1)

The wisest act, then, is that one which, when account is taken of all available data, gives us the greatest expectation of good on the balance, or the least expectation of evil on the balance. There is, of course, a difficulty as to what are to be considered available data; but broadly we can distinguish, in any given state of knowledge, things capable of being forseen from things which are unpredictable. I suppose account to be taken of the general body of current knowledge, in fact the sort of consideration which people expect when they ask for legal or medical advice. There is no doubt this brings us nearer to what is objectively right than we were when we were considering the actually most fortunate act. For one thing, it justifies the unavoidable limitation to not very distant consequences, which is almost always necessary if a practical decision is to be reached. For the likelihood of error in calculating distant consequences is so great that their contribution to the probable good or evil is very small, though their contribution to the actual good or evil is likely to be much greater than that of the nearer consequences. And it seems evident that what it is quite impossible to know cannot be relevant in judging as to what conduct is right. If, as is possible, a cataclysm is going to destroy life on this planet this day week, many acts otherwise useful will prove to have been wasted labour, for example, the preparation of next year's Nautical Almanac; but since we have no reason to expect such a cataclysm, the rightness or wrongness of acts is plainly to be estimated without regard to it. (§ 16 ¶ 2)