The recognition of this leads me to assume the existence “outside” of a process in space and time, although I do not directly perceive it at all. And the same recognition further leads me to postulate a similar process within myself, although I cannot directly perceive that either. But, as a matter of fact, I habitually postulate analogous occurrences in space and time in ordinary life which I do not directly perceive; as, for instance, when I hear piano-playing next door, and assume that a human being in space is seated at the piano and is playing upon it. And my conception, when I speak of processes happening outside of, and within me, is just the same. I assume that these processes have qualities analogous to those of the processes which do fall within the province of my senses, only that, because of certain reasons, they escape my direct perception. If I were to attempt to deny to these processes all the qualities which my senses show me in the domains of space and time, I should in reality and in truth be trying to think of something not unlike the famous knife without a handle, whose blade was wanting. Therefore, I can only say that space and time processes take place “outside” me; these bring about space and time processes “within” me; and both are necessary if the sensation “red” is to appear in my field of vision. And, in so far as this “red” is not in space and time, I shall seek for it equally in vain, whether I seek “without” or “within” myself. Those scientists and philosophers who cannot find it “outside,” ought not to want to find it “inside” either. For it is not “inside,” in exactly the same sense in which it is not “outside.” To declare that the total content of that which the sense-world presents to us is but an inner world of sensation or feeling, and then to endeavour to tack on something “external” or “outside” to it, is a wholly impossible conception.