The Six Books of Proclus on the Theology of Plato, Volume 1

Again then, let us in the next place survey the affirmations, how they exist according to the participation of the first intelligibles themselves. The supercelestial place therefore, is said to be essence which truly is, because it participates of that which is primarily being. For to be, and truly to be are present to all things, as the progeny of the intelligible essence. For as the one is from the first principle which is prior to intelligibles, so the nature of being is from intelligibles. For there the one being subsists, as Parmenides a little before taught us. But the supercelestial place is beheld by the governor of the soul, because it is allotted an intelligible transcendency with respect to the other intellectual Gods. Hence the intelligible good of it is rendered manifest from its being known by intellect. This intelligible therefore, in the same manner as that which is truly being, arrives to it from the unical Gods. For they are primarily and imparticipably intelligibles, and the first efficient causes of all intelligibles. These things also concur with each other, viz. that which is truly being, and the intelligible. For every intelligible is truly being, and every thing which is truly being is intelligible. For intellect is intelligible according to the being which is in it; but according to its gnostic power it is intellect. Hence also every intellect is the supplier of knowledge; but every intelligible is the supplier of essence. For that which each is primarily, it imparts by illumination to the secondary orders.