Commentaria in Summam contra Gentiles, Liber II

Once Alexander's position has been dispatched, St. Thomas wishes to reject the position of Galen, which seems to border on that of Alexander ¹. For Galen held that the soul is a complexion, because from different complexions we see different passions in ourselves, which are attributed to the soul, being caused; for choleric men are easily angered, while melancholic men are easily made sad.

Against this position, therefore, one could argue with the same reasons by which the opinion of Alexander was disapproved, insofar as it seems to posit, together with Alexander, that the power of the soul takes its origin from the elements; yet nevertheless Saint Thomas argues against it by proper reasons, proceeding namely from the nature of the complexion.

First, therefore, he argues as follows. The complexion is caused by active and passive powers. Therefore it cannot be the principle of the soul's operations. Therefore the soul is not a complexion. — The first consequence is proved. Because the operation of the vegetative soul, and sensitive cognition, and much more the operation of the intellect, exceed the power of the active and passive qualities: as was shown, according to Aristotle's mind, in the preceding chapter.

Second. The soul is a substantial form; otherwise, through it, no substance would come under a genus or species. Therefore it is not a complexion. — The consequence is proved. Because a complexion cannot be a substantial form, since it is something constituted from contrary qualities, and on this account it has a contrary, and admits of more and less; none of which befits a substance.

Third. The complexion does not move the animal's body by local motion. But the soul does so well enough. Therefore, etc. — The antecedent is proved: because then the animal would follow the motion of the dominant element, and thus it would always be moved downward, not in every direction, as it in fact is.

Fourth. The soul governs the body and resists the passions that follow from one's complexion: for those inclined to anger or concupiscence abstain from them because of something restraining them. But complexion does not do this. Therefore, etc.

Galen, however, seems to have been deceived, as Saint Thomas says, because he did not consider that the passions are attributed in one way to the complexion and in another to the soul. For in the passions there is something material, namely some bodily commotion; and something formal, namely the very act of the sensitive appetite; just as in anger the material element is the heat of the blood, while the formal element is the appetite for vengeance: the passions are attributed to the complexion with respect to what is material, and as to what disposes; but to the soul with respect to what is formal, and as to the principal agent.

By the same arguments the opinion of those who say the soul is a harmony is refuted, the same arguments by which the preceding opinion² was refuted: since they did not understand that the soul is a harmony not of sounds, but of contraries. This opinion indeed seems to be attributed to Empedocles in the book On the Soul; but Gregory of Nyssa attributes it to Dicaearchus³. Yet it is also refuted by arguments proper to itself.

Just as the preceding view is indeed rejected: because a harmony cannot move the body, or govern it, or resist the passions—just as neither can the bodily temperament.

It is argued against this position, however, by means of proper arguments. First. The account of harmony befits the qualities of the body more than those of the soul: as is evident from the conditions of the body, namely health, strength, and beauty; and from the conditions of the soul, which are sense and intellect, and other things pertaining to the soul. For harmony seems to belong to things of the former kind, not to things of the latter. Therefore, etc.

Second. Either the soul will be a harmony, that is, a composition; or that which is the ratio and proportion of the composition. Not the first: because then each part of the soul would be a composition of certain parts of the body; which cannot be assigned, as is evident in the case of intellect and will. Nor yet the second: because then each single part of the body would have its own soul, since in different parts of the body there are different proportions of composition; but this is clearly false. Therefore, etc.