Every type of crucial experiment proves that what we see and where we see it, depends entirely upon the physiological functioning of our body. Any method of making our body function internally in a given way, will provide us with an assigned visual sensation. The body is supremely indifferent to the happenings of nature a short way off, where it places its visual sensa.
Now the same is true of all other modes of sensation, only to a greater extent. All sense-perception is merely one outcome of the dependence of our experience upon bodily functioning. Thus if we wish to understand the relation of our personal experience to the activities of nature, the proper procedure is to examine the dependence of our personal experiences upon our personal bodies.