Summa contra Gentiles2.61 Chapter LXI. That the aforesaid opinion is contrary to that of Aristotle

Since, however, Averroes endeavours to strengthen his position by appealing to authority, and says that Aristotle was of the same opinion, we shall prove clearly that the aforesaid opinion is contrary to that of Aristotle.

First, because Aristotle {2 De Animay defines the soul by saying that the soul is the first act of an organic physical body having life potentially, and afterwards he adds' that this definition applies universally to every soul, not, as the said Averroes pretends, expressing a doubt on the point, as evidenced by the Greek text and the translation of Boethius. Afterwards in the same chapter he adds that certain parts of the soul are separable. Now these are no other than the intellective parts. It follows therefore that these parts are acts of the body.

Nor is this gainsaid by what he says afterwards Nothing so far is clear about the intellect and the power of understanding, but it would seem to be another kind of soul. For he does not wish by this to except the intellect from the common definition of a soul, but to exclude it from the natures proper to the other parts: thus he who says Animals that fly are of another kind from those that walk, does not remove the common definition of animal from those that fly. Wherefore, to show in what sense he said another he adds: And this alone can be separated as the everlasting from the corruptible. Nor is it Aristotle’s intention, as the said Commentator pretends, to say that he has not yet made it clear concerning the intellect, whether the intellect be the soul, as he had done concerning the other principles. For the genuine text does not read, nothing has been declared or nothing has been said, but nothing is clear; which we must understand as referring to that which is proper to the soul, and not as referring to the common definition. And if, as he says, soul is said equivocally of the intellect and other (souls), he (Aristotle) would first have explained the equivocation, and given the definition afterwards, as is his wont. Else his argument would have laboured under an equivocation; which is not allowable in demonstrative sciences.

Again. In 2 De Anima he reckons the intellect among the powers of the soul: and in the passage quoted’’ he calls it the power of understanding. Therefore the intellect is not outside the human soul, but is one of its powers.

Again. In the 3 De Anhna, when he begins to speak of the possible intellect, he calls it a part of the soul, for the text reads: Of the part of the soul whereby the soul has knowledge and wisdom: thus clearly indicating that the possible intellect is a part of the soul.

He is yet more explicit when he goes on to declare the nature of the possible intellect, in these words: By the intellect I mean that by which the soul knows and understands. This evidently denotes that the intellect is a part of the human soul, whereby the soul understands.

Therefore the aforesaid position is contrary to the opinion of Aristotle, and to the truth: and consequently is to be rejected as a mere fabrication.