First Principles 313 we are concerned, this is much the same thing. To assume an unknowable substratum as the source from which all things proceed or are evolved is equivalent to assuming that they come up out of nothing ; for that which does not exist for us is for us nothing ; that which we do not know does not exist qua us, and therefore it does not exist. When I say " we," I mean mankind generally, for things may exist qua one man and not qua another. And when I say " nothing " I postulate something of which we have no experience. And yet we cannot say that a thing does not exist till it is known to exist. The planet Neptune existed though, qua us, it did not exist before Adams and Leverrier discovered it, and we cannot hold that its continued non-existence to my laun- dress and her husband makes it any the less an entity. We cannot say that it did not exist at all till it was discovered, that it exists only partially and vaguely to most of us, that to many it still does not exist at all, that there are few to whom it even exists in any force or fullness and none who can realise more than the broad facts of its existence. Neptune has been dis- turbing the orbits of the planets nearest to him for more centuries than we can reckon, and whether or not he is known to have been doing so has nothing to do with the matter. If A is robbed, he is robbed, whether he knows it or not. In one sense, then, we cannot say that the planet Neptune did not exist till he was discovered, but in another we can and ought to do so. De non appareniibus et non existentibus eadem est ratio; as long, therefore, as Neptune did not appear he did not exist qua us. The only way out of it is through the contradiction in terms of maintaining that a thing exists and does not exist at one and the same time. So A may be both robbed, and not robbed. We consider, therefore, that things have assumed their present shape by course of evolution from a something which, qua us, is a nothing, from a potential something but not an actual, from an actual nothing but a potential not-nothing, from a nothing which might become a something to us with any modification on our parts but which, till such modification has arisen, does not exist in relation to us, though very con- ceivably doing so in relation to other entities. But this Pro- tean nothing, capable of appearing as something, is not the