known to be common only in so far as our personal experiences of this object prove, upon appeal to our fellows, to be verifiable in a measure sufficient to satisfy the demands of our socially critical self-scrutiny upon the level that this fashion of self-scrutiny happens in any case to have attained. Therefore, as only the definably localizable in space can be independently verified and agreed upon by a number of socially communicating beings, and as only what all can agree upon can stand the social test of externality, the principle that what is for all must, if in space at all, occupy a definite place, and have definite size and boundaries, becomes a relatively a priori principle for the things of the verifiable external world. If external things did not conform to just such principles we should in the end have no sufficient means for distinguishing them from internal things.
This instance of the way in which our conception of the very nature of an external thing is dependent for some of its essential features upon the conditions which determine our social consciousness, is an instance capable of much illustration. In my Spirit of Modern Philosophy, in a chapter entitled: The World of Description and the World of Appreciation, I have used in connection with the discussion of this topic the very obvious case of our opinions as to the physical reality of a rainbow. I see a rainbow, and believing, because of the analogy between this and other seen objects, that I see an external thing, I point out to you its place. You look, and apparently you verify my observation, for you look in the same general direction, and observe something of the same shape as I describe. For us both, at this stage of experience, the rainbow is a fully substantial physical object, because it so far stands the test of social community. So it was in our childhood. So it becomes again whenever we relapse into an uncritical fashion of thought and speech. The rainbow meets the ground at such a place; it spans the clouds thus and thus. Upon this we so far seem to agree. But later, perhaps, we become more critical, or else the mass of water-spray upon which the rainbow appears, is, in some instances, very near to
