who act upon him cause his machine to undergo.
Those who have distinguished the soul from the body, appear only to have distinguished their brain from themselves. Indeed, the brain is the common center, where all the nerves, distributed through every part of the body, meet and blend themselves: it is by the aid of this interior organ that all those operations are performed which are attributed to the soul: it is the impulse, or the motion, communicated to the nerve, which modifies the brain: in consequence, it re-acts, or gives play to the bodily organs; or rather it acts upon itself, and becomes capable of producing within itself a great variety of motion, which has been designated intellectual faculties.
From this it may be seen that some philosophers have been desirous to make a spiritual substance of the brain. It is evidently nothing but ignorance that has given birth to and accredited this system, which embraces so little, either of the natural or the rational. It is from not having studied himself, that man has supposed he was compounded with an agent, essentially different from his body: in examining this body, he will find that it is quite useless to recur to hypothesis for the explanation of the various phenomena it presents to his contemplation; that hypothesis can do nothing more than lead him out of the right road to the information after which he seeks. What obscures this question, arises from this, that man cannot see himself: indeed, for this purpose, that would be requisite which is impossible; namely, that he could he at one
