A clear and adequate conception of the scope and object-matter of a Science and its relations to other Sciences is usually arrived at only at a tolerably advanced stage in the development of the Science itself. It is impossible to start with clear conceptions of such matters as Heat, Light, Electricity, and Magnetism; for the attainment of such conceptions is precisely the goal of the Sciences which deal with these matters, and is even yet not fully reached. Science starts with some roughly defined department of common experience, and works towards clearer and more adequate conceptions of it. In the course of scientific progress, it sometimes turns out that a supposed Science deals with really non-existent objects, or is directed towards aims impossible of attainment, or that it is really identical with some Science hitherto supposed to be distinct, or is a branch of some Science the very possibility of which was unsuspected. Sciences fuse, subdivide, transform themselves, or disappear altogether; new Sciences make their appearance and new groupings of old Sciences. Thu the greatest service which Astrology ever rendered to the world was its own extinction: while it was only at a tolerably advanced stage of its development that the Science of Electricity was discovered to be identical with that of Magnetism, and not identical with the closely related but still distinguishable Sciences of Heat and Light. And, if that is the case even with the various departments of physical Science, each of which studies some group or some aspect of tangible and visible things, it is pre-eminently the case with Philosophy and general and its various branches. It is only gradually that Philosophy has clearly differentiated itself from the special Sciences, and particularly from the most general of those Sciences. The older Metaphysicians were also Physicists. It is only at a comparatively recent date that Metaphysicians have abandoned the attempt to decide by the methods of Metaphysics what were really questions of empirical Natural Science, and that Physicists have ceased to dogmatize about metaphysical questions, if indeed a well-defined conception of the relation between the two spheres can be said to have been arrived at even now: while the exact relations between the various Sciences included in or closely connected with Philosophy, such as Logic, Metaphysics, and Psychology, are still avowedly matters of dispute among Philosophers.(Bk. 1 Ch. 1 ¶ 1)

To a certain extent every student of a Science has to go through in the course of his own studies the same process which the human mind has followed in reaching the present level of scientific attainment. In the Physical Sciences this necessity is to some extent avoided by the fact that certain results of Physical Science rapidly become matters of common knowledge or social inheritance, and so are accepted unconsciously on authority even before the age at which formal scientific teaching begins. Though the results of philosophical enquiry are far from contributing nothing to the common stock of socially transmitted ideas, they pass far more slowly and incompletely into general circulation. A teacher of Astronomy does not find it necessary to begin by refuting the hypothesis that the motions of the heavenly bodies exercise a profound influence upon the life-history of individual men. In the region of Philosophy ideas of the same order cannot always be assumed to be non-existent. The very nature and meaning of Philosophy, and still more the lines of demarcation between its various branches, must be left slowly to dawn upon the student in the course of his study of Philosophy itself. Philosophy is like learning to swim. A man does not really discover what it is until he finds himself already somewhat out of his depth. He must plunge in boldly, and discover what he has been at later on.(Bk. 1 Ch. 1 ¶ 2)

For these reasons I shall make no formal attempt to mark out beforehand the relation of our subject to Philosophy in general or to its other branches. I shall begin by assuming only that we are concerned with the study of human conduct, that we are investigating the meaning of the ideas right and wrong with the object both of arriving at a clearer conception of those ideas in general, and of determining in a more precise manner than is done by ordinary persons in common life what things in particular are right and what are wrong. How far and in what sense such an aim is attainable is one of the things which must be left to appear in the course of our enquiry. And in my treatment of the subject I shall endeavour to follow what is, not indeed always but very frequently, the line of development taken by the mind of students. When first the attempt is made to think out clearly the unanalysed, more or less confused and inconsistent ideas about human conduct with which we all start, the student is very likely to be caught by a theory of extreme simplicity and apparently great scientific completeness and attractiveness--a theory which, as a matter of fact, has always made its appearance at the beginning of every serious historical effort to grapple with the ethical problem. He is very likely to be bitten by the theory which traces all human conduct to the operation of a single motive, the desire of pleasure. If this theory be true, it follows as a matter of course that the only meaning which can be given to the term right is conducive to pleasure, and to the term wrong unconducive to pleasure or productive of its opposite, pain. The commonly received ideas about right and wrong, in so far as they are upon such a view capable of scientific justification at all, have then to be explained by showing that the acts commonly regarded as right are productive of pleasure on the whole to the individual, while the actions commonly accounted wrong are conducive on the whole to pain or loss of pleasure. To examine this theory, known as psychological Hedonism, will be the starting-point of our investigation and will be dealt with in the next chapter. If satisfied that pleasure is not always the motive of the individual's own action, the student may still very probably be attracted by other forms of the theory that pleasure in the last resort, either to the individual or to others, is the sole true and ultimate criterion of human action. Utilitarianism disconnected from psychological Hedonism will be the subject of our third chapter. From the Utilitarian group of ethical theories I shall turn to their extreme opposite, the theory which asserts in the most uncompromising and unanalysed way the authority, perhaps even the infallibility, of the individual Conscience and of judgments about particular questions of right and wrong which the ordinary Conscience pronounces--the theory commonly known as Intuitionism. I shall then try to bring together the various elements of truth contained in the conflicting theories, and to arrive at a view which will embrace and harmonize them, while avoiding the mistakes and exaggerations which each, taken by itself, can be shown to involve. I shall then go on to examine more in detail some of the chief questions of right conduct, the chief commonly recognized virtues and duties or groups of duties, and to show how they can be explained and co-ordinated, with whatever correction of popular notions may turn out to be necessary, upon the basis of the theory which will be adopted.(Bk. 1 Ch. 1 ¶ 3)

To arrive at a clearer and more definite conception of the Moral Criterion--a clearer and more definite answer than is contained in that common moral consciousness from which we must all start to the question What ought I to do, and why ought I to do it? will be the object of our first book. In the second book I shall enter at greater length into some of the current controversies connected with our subject, by the examination of which I shall hope further to elucidate and define the results arrived at in the first book. Most of these controversies may be said to centre round the question of the relation of the individual and the individual's good to society and a wider social good. I have therefore styled the book The Individual and the Society. In the third book I shall deal with some of those wider philosophical issues which are ultimately involved in any attempt to think out fully and adequately the meaning of the wrods right and wrong, good and evil,--in other words with the relation of Morals and Moral Philosophy to our theory of the Universe in general, to Metaphysic and Religion, to the theory of Free-will, to the facts of Evolution and theories of Evolution, and finally to practical life. The subject of this section may be described generally as Man and the Universe. In postponing these more general considerations to the end of our enquiry instead of making them our starting-point, I am once more abandoning what may perhaps be thought the logical order; and adopting the order which will, I hope be most advantageous for purposes of exposition and dialectical defence, and which will be most convenient for those who may read this book with no previous acquaintance with technical Philosophy or with any of its branches. With regard to the relations between Metaphysic and Moral Philosophy it will be enough to premise this much--that Metaphysic is an enquiry into the ultimate nature of Reality and our knowledge of it; while Moral Philosophy is an enquiry into a particular, though very general and important, department of our knowledge, our ideas of right and wrong^[2], that is to say into one particular though very fundamental aspect of Reality, the aspect which is expressed by our moral judgments. To attain some clearer conception as to the relation of these ideas to other ideas, of this aspect of Reality to other aspects, will be one object of our investigation. but, whatever answer may be given to this last problem, it must be possible at least to begin the enquiry as to what we mean by saying that an act is right or wrong, and why we call some actions right and others wrong, without presupposing any more than is presupposed in our common unscientific thinking about the world in general and man's place in it. At a very early stage of our enquiry it may, indeed, be found that we cannot give a satisfactory answer to that question without assuming particular answers to other and more general questions about human knowledge and about the ultimate nature of things--answers which from various philosophical points of view have sometimes been implicitly or explicitly denied. But I shall endeavour, for the reasons already indicated, to make the first part of our enquiry as purely ethical as possible. If and in so far as it shall be found that to take a particular view about the ideal of human conduct, a view to which we are led purely by the investigation of the actual contents of our ethical consciousness, logically involves us in wider conclusions as to the nature of the Universe and man's place in it, that will be the best way of defending those wider conclusions, and so of exhibiting the true relation between that ethical Science which is the subject of this book and that wider Science of Reality which will be dealt with in these pages only in so far as may be necessary for the purpose of attaining clear ideas about the meaning and end of human life.(Bk. 1 Ch. 1 ¶ 4)