But this bearing upon practical Ethics, such as it is, is not what is commonly meant when it is maintained that Ethics must be based on Metaphysics. It is not the assertion of this relation which I have taken to be characteristic of Metaphysical Ethics. What metaphysical writers commonly maintain is not merely that Metaphysics can help us to decide what the effects of our actions will be, but that it can tell us which among possible effects will be good and which will be bad. They profess that Metaphysics is a necessary basis for an answer to that other and primary ethical question: What ought to be? What is good in itself? That no truth about what is real can have any logical bearing upon the answer to this question has been proved in Chapter I. To suppose that it has, implies the naturalistic fallacy. All that remains for us to do is, therefore, to expose the main errors which seem to have lent plausibility to this fallacy in its metaphysical form. If we ask: What bearing can Metaphysics have upon the question, What is good? the only possible answer is: Obviously and absolutely none. We can only hope to enforce conviction that this answer is the only true one by answering the question: Why has it been supposed to have such a bearing? We shall find that metaphysical writers seem to have failed to distinguish the primary ethical question: What is good? from various other questions; and to point out these distinctions will serve to confirm the view that their profession to base Ethics on Metaphysics is solely due to confusion. (§ 69 ¶ 1)

And, first of all, there is an ambiguity in the very question: What is good? to which it seems some influence must be attributed. The question may mean either: Which among existing things are good? or else: What sort of things are good, what are the things which, whether they are real or not, ought to be real? And of these two questions it is plain that to answer the first, we must know both the answer to the second and also the answer to this question: What is real? It asks us for a catalogue of all the good things there are in the Universe and also which of them are good. Upon this question then our Metaphysics would have a bearing, if it can tell us what is real. It would help us to complete the list of things which are both real and good. But to make such a list is not the business of Ethics. So far as it enquires What is good? its business is finished when it has completed the list of things which ought to exist, whether they do exist or not. And if our Metaphysics is to have any bearing upon this part of the ethical problem, it must be because the fact that something is real gives a reason for thinking that it or something else is good, whether it be real or not. That any such fact can give any such reason is impossible; but it may be suspected that the contrary supposition has been encouraged by the failure to distinguish between the assertion This is good, when it means This sort of thing is good, or This would be good, if it existed, and the assertion This existing thing is good. The latter proposition obviously cannot be true, unless the thing exists; and hence the proof of the thing's existence is a necessary step to its proof. Both propositions, however, in spite of this immense difference between them, are commonly expressed in the same terms. We use the same words, when we assert an ethical proposition about a subject that is actually real, and when we assert it about a subject considered as merely possible. (§ 70 ¶ 1)

In this ambiguity of language we have, then, a possible source of error with regard to the bearing of truths that assert reality upon truths that assert goodness. And that this ambiguity is actually neglected by those metaphysical writers who profess that the Supreme Good consists in an eternal reality may be shewn in the following way. We have seen, in considering the possible bearing of Metaphysics upon Practical Ethics, that, since what exists eternally cannot possibly be affected by our actions, no practical maxim can possibly be true, if the sole reality is eternal. This fact, as I said, is commonly neglected by metaphysical writers: they assert both of the two contradictory propositions that the sole reality is eternal and that its realisation in the future is a good too. Prof. Mackenzie, we saw, asserts that we ought to aim at the realisation of the true self or the rational universe: and yet Prof. Mackenzie holds, as the word true plainly implies, that both the true self and the rational universe are eternally real. Here we have already a contradiction in the supposition that what is eternally real can be realised in the future; and it is comparatively unimportant whether or not we add to this the further contradiction involved in the supposition that the eternal is the sole reality. That such a contradiction should be supposed valid can only be explained by a neglect of the distinction between a real subject and the character which that real subject possesses. What is eternally real may, indeed, be realised in the future, if by this be only meant the sort of thing which is eternally real. But when we assert that a thing is good, what we mean is that its existence or reality is good; and the eternal existence of a thing cannot possibly be the same good as the existence in time of what, in a necessary sense, is nevertheless the same thing. When, therefore, we are told that the future realisation of the true self is good, this can at most only mean that the future realisation of a self exactly like the self, which is true and exists eternally, is good. If this fact were clearly stated, instead of consistently ignored, by those who advocate the view that the Supreme Good can be defined in these metaphysical terms, it seems probable that the view that a knowledge of reality is necessary to a knowledge of the Supreme Good would lose part of its plausibility. That that at which we ought to aim cannot possibly be that which is eternally real, even if it be exactly like it; and that the eternal reality cannot possibly be the sole good—these two propositions seem sensibly to diminish the probability that Ethics must be based on Metaphysics. It is not very plausible to maintain that because one thing is real, therefore something like it, which is not real, would be good. It seems, therefore, that some of the plausibility of Metaphysical Ethics may be reasonably attributed to the failure to observe that verbal ambiguity, whereby This is good may mean either This real thing is good or The existence of this thing (whether it exists or not) would be good. (§ 70 ¶ 2)

By exposing this ambiguity, then, we are enabled to see more clearly what must be meant by the question: Can Ethics be based on Metaphysics? and we are, therefore, more likely to find the correct answer. It is now plain that a metaphysical principle of Ethics which says This eternal reality is the Supreme Good can only mean Something like this eternal reality would be the Supreme Good. We are now to understand such principles as having the only meaning which they can consistently have, namely, as describing the kind of thing which ought to exist in the future, and which we ought to try to bring about. And, when this is clearly recognised, it seems more evident that the knowledge that such a kind of thing is also eternally real, cannot help us at all towards deciding the properly ethical question: Is the existence of that kind of thing good? If we can see that an eternal reality is good, we can see, equally easily, once the idea of such a thing has been suggested to us, that it would be good. The metaphysical construction of Reality would therefore be quite useful, for the purposes of Ethics, if it were a mere construction of an imaginary Utopia: provided the kind of thing suggested is the same, fiction is as useful as truth, for giving us matter, upon which to exercise the judgment of value. Though, therefore, we admit that Metaphysics may serve an ethical purpose, in suggesting things, which would not otherwise have occurred to us, but which, when they are suggested, we see to be good; yet, it is not as Metaphysics—as professing to tell us what is real—that it has this use. And, in fact, the pursuit of truth must limit the usefulness of Metaphysics in this respect. Wild and extravagant as are the assertions which metaphysicians have made about reality, it is not to be supposed but that they have been partially deterred from making them wilder still, by the idea that it was their business to tell nothing but the truth. But the wilder they are, and the less useful for Metaphysics, the more useful will they be for Ethics; since, in order to be sure that we have neglected nothing in the description of our ideal, we should have had before us as wide a field as possible of suggested goods. It is probable that this utility of Metaphysics, in suggesting possible ideals, may sometimes be what is meant by the assertion that Ethics should be based on Metaphysics. It is not uncommon to find that which suggests a truth confused with that on which it logically depends; and I have already pointed out that Metaphysical have, in general, this superiority over Naturalistic systems; that they conceive the Supreme Good as something differing more widely from what exists here and now. But, if it be recognised that, in this sense, Ethics should, far more emphatically, be based on fiction, metaphysicians will, I think, admit that a connection of this kind between Metaphysics and Ethics would by no means justify the importance which they attribute to the bearing of the one study on the other. (§ 71 ¶ 1)