In this chapter I propose to deal with a type of ethical theory which is exemplified in the ethical views of the Stoics, of Spinoza, of Kant, and especially of a number of modern writers, whose views in this respect are mainly due to the influence of Hegel. These ethical theories have this in common, that they use some metaphysical proposition as a ground for inferring some fundamental proposition of Ethics. They all imply, and many of them expressly hold, that ethical truths follow logically from metaphysical truths—that Ethics should be based on Metaphysics. And the result is that they all describe the Supreme Good in metaphysical terms. (§ 66 ¶ 1)

What, then, is to be understood by metaphysical? I use the term, as I explained in Chapter II, in opposition to natural. I call those philosophers preeminently metaphysical who have recognised most clearly that not everything which is is a natural object. Metaphysicians have, therefore, the great merit of insisting that our knowledge is not confined to the things which we can touch and see and feel. They have always been much occupied, not only with that other class of natural objects which consists in mental facts, but also with the class of objects or properties of objects, which certainly do not exist in time, are not therefore parts of Nature, and which, in fact, do not exist at all. To this class, as I have said, belongs what we mean by the adjective good. It is not goodness, but only the things or qualities which are good, which can exist in time—can have duration, and begin and cease to exist—can be objects of perception. But the most prominent members of this class are perhaps numbers. It is quite certain that two natural objects may exist; but it is equally certain that two itself does not exist and never can. Two and two are four. But that does not mean that either two or four exists. Yet it certainly means something. Two is somehow, although it does not exist. And it is not only simple terms of propositions—the objects about which we know truths—that belong to this class. The truths which we know about them form, perhaps, a still more important subdivision. No truth does, in fact, exist; but this is peculiarly obvious with regard to truths like Two and two are four, in which the objects, about which they are truths, do not exist either. It is with the recognition of such truths as these—truths which have been called universal—and of their essential unlikeness to what we can touch and see and feel, that metaphysics proper begins. Such universal truths have always played a large part in the reasonings of metaphysicians from Plato's time till now; and that they have directed attention to the difference between these truths and what I have called natural objects is the chief contribution to knowledge which distinguishes them from that other class of philosophers—empirical philosophers—to which most Englishmen have belonged. (§ 66 ¶ 2)

But though, if we are to define metaphysics by the contribution which it has actually made to knowledge, we should have to say that it has emphasized the importance of objects which do not exist at all, metaphysicians themselves have not recognised this. They have indeed recognised and insisted that there are, or may be, objects of knowledge which do not exist in time, or at least which we cannot perceive; and in recognising the possibility of these, as an object of investigation, they have, it may be admitted, done a service to mankind. But they have in general supposed that whatever does not exist in time, must at least exist elsewhere, if it is to be at all—that, whatever does not exist in Nature, must exist in some supersensible reality, whether timeless or not. Consequently they have held that the truths with which they have been occupied, over and above the objects of perception, were in some way truths about such supersensible reality. If, therefore, we are to define metaphysics not by what it has attained, but by what it has attempted, we should say that it consists in the attempt to obtain knowledge, by processes of reasoning, of what exists but is not a part of Nature. Metaphysicians have actually held that they could give us such knowledge of non-natural existence. They have held that their science consists in giving us such knowledge as can be supported by reasons, of that supersensible reality of which religion professes to give us a fuller knowledge, without any reasons. When, therefore, I spoke above of metaphysical propositions, I meant propositions about the existence of something supersensible—of something which is not an object of perception, and which cannot be inferred from what is an object of perception by the same rules of inference by which we infer the past and future of what we call Nature. And when I spoke of metaphysical terms, I meant terms which refer to qualities of such a supersensible reality, which do not belong to anything natural. I admit that metaphysics should investigate what reasons there may be for belief in such a supersensible reality; since I hold that its peculiar province is the truth about all objects which are not natural objects. And I think that the most prominent characteristic of metaphysics, in history, has been its profession to prove the truth about non-natural existents. I define metaphysical, therefore, by a reference to supersensible reality; although I think that the only non-natural objects, about which it has succeeded in obtaining truth, are objects which do not exist at all. (§ 66 ¶ 3)

So much, I hope, will suffice to explain what I mean by the term metaphysical, and to shew that it refers to a clear and important distinction. It was not necessary for my purpose to make the definition exhaustive or to shew that it corresponds in essentials with established usage. The distinction between Nature and a supersensible reality is very familiar and very important: and since the metaphysician endeavours to prove things with regard to a supersensible reality, and since he deals largely in truths which are not mere natural facts, it is plain that his arguments, and errors (if any), will be of a more subtle kind than those which I have dealt with under the name of Naturalism. For these two reasons it seemed convenient to treat Metaphysical Ethics by themselves. (§ 66 ¶ 4)