The study of Ethics is perhaps most commonly conceived as being concerned with the questions What sort of actions ought men to perform? and What sort of actions ought men to avoid? It is conceived, that is to say, as dealing with human conduct, and as deciding what is virtuous and what is vicious among the kinds of conduct between which, in practice, people are called upon to choose. Owing to this view of the province of ethics, it is sometimes regarded as the practical study, to which all others may be opposed as theoretical; the good and the true are sometimes spoken of as independent kingdoms, the former belonging to ethics, while the latter belongs to the sciences. (§ 1 ¶ 1)

This view, however, is doubly defective. In the first place, it overlooks the fact that the object of ethics, by its own account, is to discover true propositions about virtuous and vicious conduct, and that these are just as much a part of truth as true propositions about oxygen or the multiplication table. The aim is, not practice, but propositions about practice; and propositions about practice are not themselves practical, any more than propositions about gases are gaseous. One might as well maintain that botany is vegetable or zoology animal. Thus the study of ethics is not something outside science and co-ordinate with it: it is merely one among sciences. (§ 1 ¶ 2)

In the second place, the view in question unduly limits the province of ethics. When we are told that actions of certain kinds ought to be performed or avoided, as, for example, that we ought to speak the truth, or that we ought not to steal, we may always legitimately ask for a reason, and this reason will always be concerned, not only with the actions themselves, but also with the goodness or badness of the consequences likely to follow from such actions. We shall be told that truth-speaking generates mutual confidence, cements friendships, facilitates the dispatch of business, and hence increases the wealth of the society which practices it, and so on. If we ask why we should aim at increasing mutual confidence, or cementing friendships, we may be told that obviously these things are good, or that they lead to happiness, and happiness is good. If we still ask why, the plain man will probably feel irritation, and will reply that he does not know. His irritation is due to the conflict of two feelings—the one, that whatever is true must have a reason; the other, that the reason he has already given is so obvious that it is merely contentious to demand a reason for the reason. In the second of these feelings he may be right; in the first, he is certainly wrong. In ordinary life, people only ask why when they are unconvinced. If a reason is given which they do not doubt, they are satisfied. Hence, when they do ask why, they usually have a logical right to expect an answer, and they come to think that a belief for which no reason can be given is an unreasonable belief. But in this they are mistaken, as they would soon discover if their habit of asking why were more persistent. (§ 2 ¶ 1)

It is the business of the philosopher to ask for reasons as long as reasons can legitimately be demanded, and to register the propositions which give the most ultimate reasons that are attainable. Since a proposition can only be proved by means of other propositions, it is obvious that not all propositions can be proved, for proofs can only begin by assuming something. And since the consequences have no more certainty than their premises, the things that are proved are no more certain than the things that are accepted merely because they are obvious, and are then made the basis of our proofs. Thus in the case of ethics, we must ask why such and such actions ought to be performed, and continue our backward inquiry for reasons until we reach the kind of propositions of which proof is impossible, because it is so simple or so obvious that nothing more fundamental can be found from which to deduce it. (§ 2 ¶ 2)

Now when we ask for the reasons in favour of the actions which moralists recommend, these reasons are, usually, that the consequences of the action are likely to be good, or if not wholly good, at least the best possible under the circumstances. Hence all questions of conduct presuppose the decision as to what things other than conduct are good and what bad. What is called good conduct is conduct which is a means to other things which are good on their own account; and hence the study of what is good on its own account is necessary before we can decide upon rules of conduct. And the study of what is good or bad on its own account must be included in ethics, which thus ceases to be concerned only with human conduct. (§ 3 ¶ 1)

The first step in ethics, therefore, is to be quite clear as to what we mean by good and bad. Only then can we return to conduct, and ask how right conduct is related to the production of goods and the avoidance of evils. In this, as in all philosophical inquiries, after a preliminary analysis of complex data we proceed again to build up complex things from their simpler constituents, starting from ideas which we understand though we cannot define them, and from premisses which we know though we cannot prove them. The appearance of dogmatism in this procedure is deceptive, for the premisses are such as ordinary reasoning unconsciously assumes, and there is less real dogmatism in believing them after a critical scrutiny than in employing them implicitly without examination. (§ 3 ¶ 2)