Summa contra Gentiles2.70 Chapter LXX. That according to the words of Aristotle vte must say that the intellect is united to the body as its form

Now, since Averroes endeavours to confirm his opinion especially by appealing to the words and proof of Aristotle, it remains to be shown that according to Aristotle’s opinion we must say that the intellect as to its substance is united to a body as its form.

For Aristotle in the Eighth Book of Physics proves that in movers and things moved it is impossible to go on to infinity. Whence he concludes that we must needs come to some first moved thing, which either is moved by an immovable mover, or moves itself. Of these two he takes the latter, namely that the first movable moves itself, for this reason, that what is per se always precedes that which is by another. Then he shows that a self-mover is of necessity divided into two parts, one of which is mover and the other moved. Consequently the first self-mover must consist of two parts, the one moving, the other moved. Now every such thing is animate. Wherefore the first movable, namely the heaven, is animate according to the opinion of Aristotle. Hence in 2 De Coelo it is expressly stated that the heaven is animate, and for this reason we must ascribe to the heaven differences of position not only in relation to us, but also in relation to itself. Let us then inquire with what kind of soul, according to Aristotle’s opinion, the heaven is animated.

In II Metaph. he proves that in the heaven’s movement we may consider something that moves and is wholly unmoved, and something that moves and is also moved. Now that which moves and is wholly unmoved, moves as an object of desire, desirable of course by that which is moved. And he shows that it moves not as desirable by the desire of concupiscence, which is the desire of sense, but as desirable by intellectual desire: wherefore he says that the first unmoved mover is desirable and intellectual. Consequently that which is moved by it, namely the heaven, is desiring and understanding in a more noble way than we are, as he proves further on. Therefore the heaven is composed, according to Aristotle’s opinion, of an intellectual soul and a body. He refers to this when he says (2 De AnimaY that in certain things there is the faculty and act of understanding, for instance in men, and in any other like or more noble things, namely the heaven.

Now it is clear that the heaven has not a sensitive soul, according to the opinion of Aristotle; since it would have various organs, which is not in keeping with the heaven’s simplicity. In order to point this out Aristotle goes on to say that those corruptible things which have intellect have all the other powers, so as to imply that some incorruptible things, namely the heavenly bodies, have intellect without the other powers of the soul.

Therefore it cannot be said that the intellect comes into contact with the heavenly bodies through phantasms: but we must say that the intellect, by its substance, is united to the heavenly body as its form.

Consequently, since the human body is the most noble of all lower bodies, and by the equability of its temperament is most like the heaven which is free of all contrariety, it follows that in the opinion of Aristotle, the intellectual substance is united to the human body not by any phantasms, but as its form.

As regards what we have said about the heaven being animate, we have not said it as though we asserted it to be in keeping with the teaching of faith, to which it matters not whether we state it to be so or otherwise. Hence Augustine says (Enchir.) Nor do I consider it as certain whether the sun, moon, and all the stars belong to the same company, i.e. of the angels; although some think them to be bodies endowed with light, without sense or intelligence.