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.