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)

But (3) it is plain that even this is a task of immense difficulty. It is difficult to see how we can establish even a probability that by doing one thing we shall obtain a better total result than by doing another. I shall merely endeavour to point out how much is assumed, when we assume that there is such a probability, and on what lines it seems possible that this assumption may be justified—that no sufficient reason has ever yet been found for considering one action more right or more wrong than another. (§ 93 ¶ 1)

(a) The first difficulty in the way of establishing a probability that one course of action will give a better total result than another, lies in the fact that we have to take account of the effects of both throughout an infinite future. We have no certainty but that, if we do one action now, the Universe will, throughout all time, differ in some way from what it would have been, if we had done another; and, if there is such a permanent difference, it is certainly relevant to our calculation. But it is quite certain that our causal knowledge is utterly insufficient to tell us what different effects will probably result from two different actions, except within a comparatively short space of time; we can certainly only pretend to calculate the effects of actions within what may be called an immediate future. No one, when he proceeds upon what he considers a rational consideration of effects, would guide his choice by any forecast that went beyond a few centuries at most; and, in general, we consider that we have acted rationally, if we think we have secured a balance of good within a few years or months or days. Yet, if a choice guided by such considerations is to be rational, we must certainly have some reason to believe that no consequences of our action in a further future will generally be such as to reverse the balance of good that is probable in the future which we can forsee. This large postulate must be made, if we are ever to assert that the results of one action will be even probably better than those of another. Our utter ignorance of the far future gives us no justification for saying that it is even probably right to choose the greater good within the region over which a probable forecast may extend. We do, then, assume that it is improbable that effects, after a certain time, will, in general, be such as to reverse the comparative value of the alternative results within that time. And that this assumption is justified must be shewn before we can claim to have given any reason whatever for acting in one way rather than in another. It may, perhaps, be justified by some such considerations as the following. As we proceed further and further from the time at which alternative actions are open to us, the events of which either action would be part cause become increasingly dependent on those other circumstances, which are the same, whichever action we adopt. The effects of any individual action seem, after a sufficient space of time, to be found only in trifling modifications spread over a very wide area, whereas its immediate effects consist in some prominent modification of a comparatively narrow area. Since, however, most of the things which have any great importance for good or evil are things of this prominent kind, there may be a probability that after a certain time all the effects of any particular action become so nearly indifferent, that any difference between their value and that of the effects of another action, is very unlikely to outweigh an obvious difference in the value of the immediate effects. It does in fact appear to be the case that, in most cases, whatever action we now adopt, it will be all the same a hundred years hence, so far as the existence at that time of anything greatly good or bad is concerned: and this might, perhaps, be shewn to be true, by an investigation of the manner in which the effects of any particular event become neutralsed by lapse of time. Failing such a proof, we can certainly have no rational ground for asserting that one of two alternatives is even probably right another wrong. If any of our judgments of right and wrong are to pretend to probability, we must have reason to think that the effects of our actions in the far future will not have value sufficient to outweigh any superiority of one set of effects over another in the immediate future. (§ 93 ¶ 2)