Whatever is not in the concept of the essence or the quiddity comes from beyond the essence and makes a composition with the essence, because no essence can be understood without the things that are its parts. But every essence or quiddity can be understood without understanding anything about its existence: I can understand what a man is or what a phoenix is and nevertheless not know whether either has existence in reality. Therefore, it is clear that existence is something other than the essence or quiddity, unless perhaps there is something whose quiddity is its very own existence, and this thing must be one and primary. For, there can be no plurification of something except by the addition of some difference, as the nature of a genus is multiplied in its species; or as, since the form is received in diverse matters, the nature of the species is multiplied in diverse individuals; or again as when one thing is absolute and another is received in something else, as if there were a certain separate heat that was other than unseparated heat by reason of its own separation. But if we posit a thing that is existence only, such that it is subsisting existence itself, this existence will not receive the addition of a difference, for, if there were added a difference, there would be not only existence but existence and also beyond this some form; much less would such a thing receive the addition of matter, for then the thing would be not subsisting existence but material existence. Hence, it remains that a thing that is its own existence cannot be other than one, and so in every other thing, the thing's existence is one thing, and its essence or quiddity or nature or form is another. In the intelligences, therefore, there is existence beyond the form, and so we say that an intelligence is form and existence.
Everything that pertains to a thing, however, either is caused by the principles of its own nature, as risibility in man, or else comes from some extrinsic principle, as light in the air from the influence of the sun. Now, it cannot be that existence itself is caused by the very form or quiddity of the thing (I mean as by an efficient cause), because then the thing would be its own efficient cause, and the thing would produce itself in existence, which is impossible. Therefore, everything the existence of which is other than its own nature has existence from another. And since everything that is through another is reduced to that which is through itself as to a first cause, there is something that is the cause of existing in all things in that this thing is existence only. Otherwise, we would have to go to infinity in causes, for everything that is not existence alone has a cause of its existence, as said above. It is clear, therefore, that the intelligences are form and existence and have existence from the first being, which is existence alone, and this is the first cause, which is God.
Everything that receives something from another is in potency with respect to what it receives, and that which is received in the thing is its act;therefore, a quiddity or form that is an intelligence is in potency with respect to the existence that it receives from God, and this received existence is received as its act. And thus there are found in the intelligences both potency and act but not matter and form, unless in some equivocal sense.
So too to suffer, to receive, to be a subject and everything of this type that seem to pertain to things by reason of their matter are said of intellectual substances and corporeal substances equivocally, as the Commentator says in De Anima III, com. 14. Furthermore, since, as said above, the quiddity of an intelligence is the intelligence itself, its quiddity or essence is itself the very thing that exists, and its existence received from God is that by which it subsists in the nature of things; and because of this some people say that substances of this kind are composed of what is and that by which it is, or of what is and existence, as Boethius says in De Hebdomadibus (PL 64, 1311 B-C).
Moreover, since we posit in the intelligences potency and act, it will not be difficult to find a multitude of intelligences, which would be impossible if there were in them no potency. Hence, the Commentator says in De Anima III, com. 5 that if the nature of the possible intellect were unknown, we would not be able to find a multitude of separate substances.
There is thus a distinction among separate substances according to their grade of potency and act such that the superior intelligences, which are nearer the first cause, have more act and less potency, and so on.
This scale comes to an end with the human soul, which holds the lowest place among intellectual substances. The soul's possible intellect is related to intelligible forms just as prime matter (which holds the lowest place in sensible existence) is related to sensible forms, as the Commentator says in De Anima III, com. 5. The Philosopher thus compares, III De Anima cap. 4 (430a1), the soul to a tablet on which nothing has been written. Since, among intellectual substances, the soul has the most potency, it is so close to material things that a material thing is brought to participate in its existence: that is, from the soul and the body there results one existence in one composite thing, although this existence, as the existence of the soul, is not dependent on the body. Therefore, beyond this form that is the soul, there are other forms having more potency and being closer to matter, and so much so that they have no existence without matter. Among these forms there is an order and gradation down to the primary forms of the elements, which are closest to matter; and so these have no operation except as required by the active and passive qualities and other such qualities by which matter is disposed by form.
