us, as in the case of rainbows in mountain mists. And now we find that, as a fact, no two of us can ever see the rainbow at precisely the same place, as defined by reference to other objects already agreed upon. When once we have discovered this fact, we come to agree that a rainbow cannot, as it is seen, be the real physical thing at all. It must be a show thing, based upon physical realities, whose nature becomes a topic for further investigation. Here, you see, the possibility of mutual verification of our space—localizations—is used in a relatively a priori fashion to distinguish between the internal and the external facts of our experience. If the visible rainbow were an externally substantial object, it would have the same verifiable place for all percipients. As it has not, it cannot be a substantial outer thing.
What holds of spatial localization, holds of a number of other essential characters of the things of the external world. The internal world is essentially a world of experiences that may or may not be definite, but that at least need not be definable. The outer world, in so far as it is verifiably outer, is essentially the world whose presence can only be indicated to you by your definable, communicable experiences. You may feel as vague, as indescribable, as unintelligibly absurd things as you will or as you do not will. And yet these feelings may, in their internal character, be as irresistibly real facts as, in the external world, granite mountains are real. For the internal is of course not unreal ; but its reality differs from what we name outer reality in that the internal is subject a priori to no principle of definiteness, but may be either chaos or order as you find it. On the other hand, the outer world, as such, is essentially the determinate world. For unless you found it determinate, you could not communicate to your fellow, for his verification, a definite account of it. Its things, accordingly, are conceived as having sharp outlines, definable characters. You have to commit yourself to precise principles whenever you speak of its facts. The difference between the inner, with the beautiful and indefinable privacy of many of its experiences, and the outer, with the essential
