I have more than one Therefore. A body is capable only of motion, although, to be sure, that motion is only the show of the aforementioned combination and the result of the powers concealed in simple parts. The string, the air, the auditory ossicles, the auricular nerves, vibrate; but the vibration of the latter no more explains the sensation of a tone than the vibration of the string could, if the soul were chained to that. Thus, despite all images in the eye and brain, the _discernment_ of them is still not yet made out or explained; or will you say, perhaps, that for some such reason as this, because the senses are _mirrors_ full of images, therefore the spiritual _eye_ is dispensed with or made good? And does not the change of the nerve presuppose a second in a second essence, if it is to be perceived? Or does another motion in this essence represent the first motion? This brings me to the brain. That greatest and grossest nerve--the sounding-board of all the others--shows up to the soul the delineations of those images which are introduced by the rest. Upon the whole, I am of opinion that the brain serves more the nerves of the muscles, the veins of the limbs, which meet in the hand of the soul, and all, in fact, more as nourishing root, than it serves as a case of instruments to the pictorial soul. As most of our ideas are served up on visual images, and take from them their ground color, it is probable we think more with the optic nerve than with the brain. Why is it, as Bonnet has observed, that deep-thinking wearies the eyes and sharp-seeing the brain? Why do certain excesses blunt at the same time the memory and the eyes? The fever-images playing their antics outside of the eyes of the sick and people of lively fancy, like Cardan, who saw in the dark whatever he thought vividly and glowingly, are explained in my hypothesis.