Page:Mind and the Brain (1907).djvu/251

 that the consciousness, directly aroused by a nerve-wave, does not perceive this undulation, but in its stead the external object. Let us first note that between the external object and the nervous influx there is the relation of cause to effect. It is only the effect which reaches us, our nerve cells, and our consciousness. What must be explained is how a cognition (if such a word may be employed here) of the effect can excite the consciousness of the cause. It is clear that the effect does not resemble the cause, as quality: the orange I am looking at has no resemblance with the brain wave which at this moment is traversing my optic nerve; but this effect contains everything which was in the cause, or, more exactly, all that part of the cause of which we have perception. Since it is only by the intermediary of our nervous system that we perceive the object, all the properties capable of being perceived are communicated to our nervous system and inscribed in the nerve wave. The effect produced therefore is the measure of our perception of the cause. This is absolutely certain. All bodies possess an infinity of properties which escape our cognitions; because, as excitants of our organism, these properties are wanting in the intensity or the quality necessary to make it vibrate; they have not been tuned in unison with our nervous chords. And, inversely, all we perceive