As I am quoting Descartes, who, I ask, more clearly than Descartes has perceived that the soul can have only a very circumscribed seat in the economy, and that that circumscribed seat is the brain itself?
“We know,” says he, “that, properly speaking, it is not inasmuch as the soul is in the members that serve as organs to the exterior senses, that the soul feels, but inasmuch as she is in the brain, where she exercises the faculty denominated common sense.”[11]
He elsewhere observes: “Surprise is expressed because I do not recognise any other point of sensation except that which exists in the brain; but all physicians and surgeons will, I hope, assist me in proving this point, for they are aware of the common fact that a person who has been subjected to amputation of a limb, continues to feel pain in a part that he no longer possesses.”[12]
Here then, according to Descartes, we find that the soul is situated, that is to say, feels in the brain, and only in the brain. The following passage shows with what precision he excluded even the external senses from any participation with the functions of the soul.
“I have shown,” says he, “that size, distance, and form are perceived only by the reason; and that, by deducing them the one from the other.”[13]
“I cannot agree with the assertion that this error (the error caused by the bent appearance of a stick partly plunged into water,) is not corrected by the understanding but by the touch; for, although the sense in question makes us judge that the stick is straight, yet that cannot correct the error of vision; but furthermore, it is requisite that reason should teach us to confide, in this case, rather to our judgment after touching, than to the judgment that we come to after using our eyes; but this reason cannot be attributed to the sense, but to the understanding alone; and in this very example, it is the understanding that corrects the error of the sense.”[14]
The brain, then, is the exclusive seat of the soul; and all sensation, even those operations that appear to depend upon the simple external sense, is function of the soul.
Gall falls back upon Condillac, who, much less rigorous in this particular than Descartes, says, that “all our faculties proceed from the senses.”[15] But when Condillac speaks thus, he evidently speaks by ellipsis, for he immediately adds these words: “The senses are only occasional causes. They do not feel; it is the soul that alone feels, through the medium of the organs.”[16]
Now, if it be the soul only that feels, à fortiori, it is the soul only that remembers, that judges, that imagines, &c. Memory, judgment, imagination, &c., in a word, all our faculties, are therefore of the soul, and therefore come from the soul, and not from the senses.
There is no philosopher who has exaggerated more than Helvetius the influence of the senses upon the intelligence. But Helvetius says, “In whatsoever manner we interrogate experience, she always answers that any greater or lesser superiority of mind is independent of any greater or lesser perfection of the senses.”[17]