He rejected the unity and transcendence of the agent...

He rejected the unity and transcendence of the agent intellect not only for theological but for philosophical reasons. As Aquinas observes 1, he who receives an intelligible form does not thereby become an "intelligent being." For instance, a house which receives the intelligible form of the idea of the artist, is intelligible but not intelligent. Man not only is intelligible but also intelligent; he is intelligent, because he make intelligent operations.

The principle of these intelligent operations, therefore, must be the soul itself and not a separate intellect. 2 The second question deals with the relationship of the human soul to the body. In man there are many operations -- vegetative, sensitive, and intellective. Now, unquestionably the intellective operations are performed by the rational soul. But who performs the others?

Platonic-Augustinian philosophy solved the question by admitting a multiplicity of inferior forms which are subordinated to the rational soul. Thus there was a sensitive form as well as a vegetative form. Aquinas, following Aristotle in this matter, denies any multiplicity of substantial forms in the same individual. The form for man is one as is the form for any individual thing; in man this form is the rational soul. It is the principle of all operations, whether material or spiritual.

We know that the one soul understands and performs all the operations. We express this identity of the subject when we say: "I understand and I feel, and I see." Proper to the human soul is the understanding, which does not need the cooperation of any organ in its operations.

But the human soul is also the "form of the body"; and just as every form is the principle of all the operations of the informed matter, so also the human soul is the principle of all operations performed by the body through its various organs. 3 The doctrine that "the soul is the form of the body" gives rise to another difficulty, which seems to spring from the same principle of matter and form taken from Aristotelian metaphysics.

According to Aristotle, the forms of natural bodies depend on the conditions of matter, so that when these conditions become unfit the permanence of the form is no longer possible; then it will be corrupted and another form will take its place. Hence the doctrine of the soul as the unique form of the body seems to lead logically to the mortality of the human soul. Aquinas overcomes the difficulty with the same Aristotelian principles.