where, viz., in certain neural processes and in those alone. What the 'argument from relativity,' or (as it is sometimes called) the 'physiological argument,' really proves is that the existence of any immediately experienced object is conditioned by the relations of other objects (viz., the elements of the nervous system), which are not themselves perceived at the same time as the object whose existence they condition. That is to say, I cannot see an object and at the same time perceive the retinal changes which make my vision of it possible. It is only indirectly and by another set of experiences that I become aware of the physiological apparatus which has made possible the perception of objects which, at the time they were perceived, appeared to be wholly outside and independent of that apparatus. In short, the physiological argument is not a proof of idealism, although it is a disproof of what has sometimes been called 'naïve realism,'—the doctrine which holds that all immediately experienced objects exist just as, and just where, they, at any one moment, and to any one person, appear; that things always are precisely what they seem. Of course the physiological idealist has little difficulty in pointing, in refutation of this view, to such things as the objects of dreams and hallucinations, which certainly appear to exist independently and in outer space, but which can be shown to have no true place outside the organism of the percipient, and to depend entirely upon the conditions of that organism. And it is equally easy to show that in normal and waking life the objects of immediate experience are no less dependent upon our neural processes. For example, the sound and the flash are perceived to issue at different times from a distant cannon, while it can be proved that in reality they occurred there simultaneously, the interval of time perceived between them being in reality the interval between their effects upon the eye and the ear. And again the star, which we 'perceive' in the sky, may be proved by the astronomer not to be there at all, but to have perished years before; the only objective reality now existing being the effect upon the eye of the light emitted by the star prior to its destruction. From such facts as these, the idealist jumps to the conclusion that all objects depend for their existence on
