That this is the case, that the questions, What is right? what is my duty? what ought I to do? belong exclusively to this third branch of ethical enquiry, is the first point to which I wish to call attention. All moral laws, I wish to shew, are merely statements that certain kinds of actions will have good effects. The very opposite of this view has been generally prevalent in Ethics. The right and the useful have been supposed to be at least capable of conflicting with one another, and, at all events, to be essentially distinct. It has been characteristic of a certain school of moralists, as of moral common sense, to declare that the end will never justify the means. What I wish first to point out is that right does and can mean nothing but cause of a good result, and is thus identical with useful; whence it follows that the end always will justify the means, and that no action which is not justified by its results can be right. That there may be a true proposition, meant to be conveyed by the assertion The end will not justify the means, I fully admit: but that, in another sense, and a sense far more fundamental for ethical theory, it is utterly false, must first be shewn. (§ 88 ¶ 3)

That the assertion I am morally bound to perform this action is identical with the assertion This saction will produce the greatest amount of good in the Universe has already been briefly shewn in Chap I (§ 17); but it is important to insist that this fundamental point is demonstrably certain. This may, perhaps, be best made evident in the following way. It is plain that when we assert that a certain action is our absolute duty, we are asserting that the performance of that action at that time is unique in respect of value. But no dutiful action can possibly have unique value in the sense that it is the sole thing of value in the world; since, in that case, every such action would be the sole good thing, which is a manifest contradiction. And for the same reason its value cannot be unique in the sense that it has more intrinsic value than anything else in the world, since every act of duty would then be the best thing in the world, which is also a contradiction. It can, therefore, be unique only in the sense that the whole world will be better, if it be performed, than if any possible alternative were taken. And the question whether this is so cannot possibly depend solely on the question of its own intrinsic value. For any action will also have effects different from those of any other action; and if any of these have intrinsic value, their value is exactly as relevant to the total goodness of the Universe as that of their cause. It is, in fact, evident that, however valuable an action may be in itself, yet, owing to its existence, the sum of good in the Universe may conceivably be made less than if some other action, less valuable in itself, had been performed. But to say that this is the case is to say that it would have been better that the action should not have been done; and this again is obviously equivalent to the statement that it ought not to have been done—that it was not what duty required. Fiat iustitia, ruat caelum can only be justified on the ground that by the doing of justice the Universe gains more than it loses by the falling of the heavens. It is, of course, possible that this is the case: but, at all events, to assert that justice is a duty, in spite of such consequences, is to assert that it is the case. (§ 89 ¶ 2)

Our duty, therefore, can only be defined as that action, which will cause more good to exist in the Universe than any possible alternative. And what is right or morally permissible only differs from this, as what will not cause less good than any possible alternative. When, therefore, Ethics presumes to assert that certain ways of acting are duties it presumes to assert that to act in those ways will always produce the greatest possible sum of good. If we are told that to do no murder is a duty, we are told that the action, whatever it may be, which is called murder, will under no circumstances cause so much good to exist in the Universe as its avoidance. (§ 89 ¶ 3)

But, if this be recognised, several most important consequences follow, with regard to the relation of Ethics to conduct. (§ 90 ¶ 1)

(1) It is plain that no moral law is self-evident, as has commonly been held by the Intuitional school of moralists. The Intuitional view of Ethics consists in the supposition that certain rules, stating that certain actions are always to be done or to be omitted, may be taken as self-evident premisses. I have shewn with regard to judgments of what is good in itself, that this is the case; no reason can be given for them. But it is the essence of Intuitionism to suppose that rules of action—statements not of what ought to be, but of what we ought to do—are in the same sense intuitively certain. Plausibility has been lent to this view by the fact that we do undoubtedly make immediate judgments that certain actions are obligatory or wrong: we are thus often intuitively certain of our duty, in a psychological sense. But, nevertheless, these judgments are not self-evident and cannot be taken as ethical premisses, since, as has now been shewn, they are capable of being confirmed or refuted by an investigation of causes and effects. It is, indeed, possible that some of our immediate intuitions are true; but since what we intuit, what conscience tells us, is that certain actions will always produce the greatest sum of good possible under the circumstances, it is plain that reasons can be given, which will shew the deliverances of conscience to be true or false. (§ 90 ¶ 2)

(2) In order to shew that any action is a duty, it is necessary to know both what are the other conditions, which will, conjointly with it, determine its effects; to know exactly what will be the effects of these conditions; and to know all the events which will be in any way affected by our action throughout an infinite future. We must have all this causal knowledge, and further we must know accurately the degree of value both of the action itself and of all these effects; and must be able to determine how, in conjunction with the other things in the Universe, they will affect its value as an organic whole. And not only this: we must also possess all this knowledge with regard to the effects of every possible alternative; and must then be able to see by comparison that the total value due to the existence of the action in question will be greater. But it is obvious that our causal knowledge alone is far too incomplete for us ever to assure ourselves of this result, that an action is our duty: we can never be sure that any action will produce the greatest value possible. (§ 91 ¶ 1)

Ethics, therefore, is quite unable to give us a list of duties: but there still remains a humbler task which may be possible for Practical Ethics. Although we cannot hope to discover which, in a given situation, is the best of all possible alternative actions, there may be some possibility of shewing which among the alternatives, likely to occur to any one, will produce the greatest sum of good. This second task is certainly all that Ethics can ever have accomplished: and it is certainly all that it has ever collected materials for proving; since no one has ever attempted to exhaust the possible alternative actions in any particular case. Ethical philosophers have in fact confined their attention to a very limited class of actions, which have been selected because they are those which most commonly occur to mankind as possible alternatives. With regard to these they may possibly have shewn that one alternative is better, i.e. produces a greater total of value, than others. But it seems desirable to insist, that though they have represented this result as a determination of duties, it can never really have been so. For the term duty is certainly so used that, if we are subsequently persuaded that any possible action would have produced more good than the one we adopted, we admit that we failed to do our duty. It will, however, be a useful task if Ethics can determine which among alternatives likely to occur will produce the greatest total value. For, though this alternative cannot be proved to be the best possible, yet it may be better than any course of action which we should otherwise adopt. (§ 91 ¶ 2)

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 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 that it was a pity that a man did his duty. (§ 92 ¶ 1)

We must, therefore, distinguish a possible action from an action of which it is possible to think. By the former we mean an action which no known cause would prevent, provided the idea of it occurred to us: and that one among such actions, which will produce the greatest total good, is what we mean by duty. Ethics certainly cannot hope to discover what kind of action is always our duty in this sense. It may, however, hope to decide which among one or two such possible actions is the best: and those which it has chosen to consider are, as a matter of fact, the most important of those with regard to which men deliberate whether they shall or shall not do them. A decision with regard to these may therefore be easily confounded with a decision with regard to which is the best possible action. But it is to be noted that even though we limit ourselves to considering which is the better among alternatives likely to be thought of, the fact that these alternatives might be thought of is not included in what what we mean by calling them possible alternatives. Even if in any particular case it was impossible that the idea of them should have occurred to a man, the question we are concerned with is, which, if it had occurred, would have been the best alternative? If we say that murder is always a worse alternative, we mean to assert that it is so, even where it was impossible for the murderer to think of doing anything else. (§ 92 ¶ 2)

The utmost, then, that Practical Ethics can hope to discover is which, among a few alternatives possible under certain circumstances, will, on the whole, produce the best result. It may tell us which is the best, in this sense, of certain alternatives about which we are likely to deliberate; and since we may also know that, even if we choose none of these, what we shall, in that case, do is unlikely to be as good as one of them, it may thus tell us which of the alternatives, among which we can choose, it is best to choose. If it could do this it would be sufficient for practical guidance. (§ 92 ¶ 3)