the soul is divided into three faculties; one merely of growth and vegetation, such as is found in plants; another which relates to the senses, which is preserved in the nature of irrational animals; but the perfect faculty of the soul is that of reason, which is seen in human nature. By saying then the heart, He signified the bodily substance, that is, the vegetative; by the soul the middle, or the sensitive; but by saying the mind, the higher nature, that is, the intellectual or reflective faculty.
Reproduced in full. Translation: Oxford 1841 (Newman), public domain (Public domain).
Also cites: de Hom. Opif. c. 8.