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