subjective "Eppur si muove" of the experience of the after-images of motion. Try the experiment and see. Nobody can imitate the happening in this case as a happening to the objects that are seen thus to move and to rest at once. One can only define the experience by mentioning the paradox. Could one define positively and in general terms this sort of resting motion, could one set forth what appears to happen to objects when they thus restlessly rest, one would be dealing with a character of things that might very well demand that we should call it objective, if only the experience of such a character became sufficiently frequent and important in its physical relations.
Suppose namely, that this sort of movement without change of place occurred frequently in our experience, and appeared as associated, in definable ways, not with certain of our after-images, but with those characters of given things which we had already come to regard as representative of external realities. Suppose, for instance, that this moveless sort of motion appeared at once in any body that we introduced into a given magnetic field, and persisted or varied in definite ways under definable conditions. Then, indeed, we should get a definition of the resting motion as an event with definable space and time relations of the objects concerned. We should at once come to regard the phenomenon in question as at least relatively objective. As a fact, we do even now regard this phenomenon of subjective motion as dependent upon, and in so far indicative of, actual physical conditions, e.g., conditions of retinal or of central nervous stimulation. But why do we do this? I answer, any frequently repeated verifiable phenomenon gets linked to the properties of things in our external world precisely in so far as you can define, in general, i.e., in communicable terms, the conditions, spatial and temporal, under which the phenomenon in question can be produced and verified. These definable conditions, as it chances, relate, in case of these after-images of motion, to nothing that can be described as happening to the objects A, B, and C, whose paradoxical seeming behavior can only be felt, and cannot be stated in general terms. For they change in this case neither
