Enneads II.5: Of the Aristotelian Distinction Between Actuality and Potentiality
Intelligible Matter Is Not Potential
3. The purpose of the preceding considerations was to determine the meaning of the statement that intelligibles are actual; to decide whether every intelligible exist only actually, or whether it be only an actuality; and third, how even up there in the intelligible, where all things are actualities, there can also exist something potentially. If, then, in the intelligible world, there be no matter which might be called potential, if no being is to become something which it is not yet, nor transform itself, nor, while remaining what it is, beget something else, nor by altering, cause any substitution, then there could not be anything potential in this World of eternal essence outside of time. Let us now address the following question to those who admit the existence of matter, even in intelligible things: "How can we speak of matter in the intelligible world, if by virtue of this matter nothing exists potentially? For even if in the intelligible world matter existed otherwise than it does in the sense-world, still in every being would be the matter, the form and the compound which constitutes it." They would answer that in intelligible things, what plays the part of matter is a form, and that the soul, by herself, is form; but, in relation to something else, is matter. Is the soul then potential in respect of this other thing? Hardly, for the soul possesses the form, and possesses it at present, without regard to the future, and she is divisible in form and matter only for reason; if she contain matter, it is only because thought conceives of her as double (by distinguishing form and matter in her). But these two things form a single nature, as Aristotle also says that his "quintessence" is immaterial.
THE SOUL IS THE PRODUCING POTENTIALITY; NOT THE POTENTIALITY OF BECOMING.
What shall we say? Potentially, she is the animal, when it is unborn, though to be born. Potentially she is the music, and all the things that become, because they are transient. Thus in the intelligible world there are things which exist, or do not exist potentially. But the soul is the potentiality of these things.[22]