Gall avers, and this is the second fundamental proposition of his doctrine, that the brain is divided into several organs, each one of which lodges a particular faculty of the soul. By the word brain, he understood the whole brain, and he thus deceived himself. Let us reduce the application of his proposition to the hemispheres alone, and we shall see that he has deceived himself again.
It has been shown by my late experiments, that we may cut away, either in front, or behind, or above, or on one side, a very considerable slice of the hemisphere of the brain, without destroying the intelligence. Hence it appears, that quite a restricted portion of the hemispheres may suffice for the purposes of intellection in an animal.[22]
On the other hand, in proportion as these reductions by slicing away the hemispheres are continued, the intelligence becomes enfeebled, and grows gradually less; and certain limits being passed, is wholly extinguished. Hence it appears, that the cerebral hemispheres concur, by their whole mass, in the full and entire exercise of the intelligence.[23]
In fine, as soon as one sensation is lost, all sensation is lost; when one faculty disappears, all the faculties disappear. There are not, therefore, different seats for the different faculties, nor for the different sensations. The faculty of feeling, of judging, of willing any thing, resides in the same place as the faculty of feeling, judging, or willing any other thing, and consequently this faculty, essentially a unit, resides essentially in a single organ.[24]
The understanding is, therefore, a unit.
According to Gall, there are as many particular kinds of intellect as there are distinct faculties of the mind. According to him, each faculty has its perception, its memory, its judgment, will, &c., that is to say, all the attributes of the understanding, properly so called.[25]
“All the intellectual faculties,” says he, “are endowed with the perceptive faculty, with attention, recollection, memory, judgment, and imagination.”[26]
Thus each faculty perceives, remembers, judges, imagines, compares, creates; but these are trifles—for each faculty reasons. “Whenever,” says Gall, “a faculty compares and judges of the relations of analogous or different ideas, there is an act of comparison, there is an act of judgment: a sequence of comparisons and judgments constitutes reasoning,” &c.[27]