The Six Enneads
The Three Initial Hypostases (8)
This is the explanation of Plato's Triplicity, in the passage where he names as the Primals the Beings gathered about the King of All, and establishes a Secondary containing the Secondaries, and a Third containing the Tertiaries. He teaches, also, that there is an author of the Cause, that is of the Intellectual-Principle, which to him is the Creator who made the Soul, as he tells us, in the famous mixing bowl. This author of the causing principle, of the divine mind, is to him the Good, that which transcends the Intellectual-Principle and transcends Being: often too he uses the term "The Idea" to indicate Being and the Divine Mind. Thus Plato knows the order of generation- from the Good, the Intellectual-Principle; from the Intellectual-Principle, the Soul. These teachings are, therefore, no novelties, no inventions of today, but long since stated, if not stressed; our doctrine here is the explanation of an earlier and can show the antiquity of these opinions on the testimony of Plato himself. Earlier, Parmenides made some approach to the doctrine in identifying Being with Intellectual-Principle while separating Real Being from the realm of sense. "Knowing and Being are one thing he says, and this unity is to him motionless in spite of the intellection he attributes to it: to preserve its unchanging identity he excludes all bodily movement from it; and he compares it to a huge sphere in that it holds and envelops all existence and that its intellection is not an outgoing act but internal. Still, with all his affirmation of unity, his own writings lay him open to the reproach that his unity turns out to be a multiplicity. The Platonic Parmenides is more exact; the distinction is made between the Primal One, a strictly pure Unity, and a secondary One which is a One-Many and a third which is a One-and-many; thus he too is in accordance with our thesis of the Three Kinds.
VIII, Chapter II (1)
Prior to truly existing beings and total principles [or principles that rank as wholes], there is one God, prior to [that deity who is generally...
(1) Prior to truly existing beings and total principles [or principles that rank as wholes], there is one God, prior to [that deity who is generally believed to be] the first God and king, immoveable, and abiding in the solitude of his own unity. For neither is the intelligible connected with him, nor any thing else; but he is established as the paradigm of the God who is the father of himself, is self begotten, is father alone, and is truly good. For he is something even greater and prior to this, is the fountain of all things, and the root of the first intelligible forms. But from this one deity, the God who is sufficient to himself unfolds himself, into light. For this divinity, also, is the principle and God of Gods, a monad from the one , prior to essence, and the principle of essence. For from him entity and essence are derived; and hence, also, he is denominated the principle of intelligibles. These, therefore, are the most ancient principles of all things, which Hermes arranges prior to the etherial, empyrean, and celestial Gods. He likewise delivered to us the history of the empyrean Gods in one hundred books; of the etherial in an equal number; and of the celestial in a thousand books.
The Works of Dionysius the Areopagite
On Divine Names, Caput V (8)
Yea, even the all holy and most honoured Powers veritably being, and established, as it were, in the vestibule of the superessential Triad, are from I...
(8) And from the same Cause of all, are the higher and lower intellectual essences of the godlike angels; and those of the souls; and the natures of the whole Cosmos; all things whatsoever said to be either in others, or by reflection. Yea, even the all holy and most honoured Powers veritably being, and established, as it were, in the vestibule of the superessential Triad, are from It, and in It; and have the being and the godlike being; and after them, as regards Angels, the subordinate, subordinately, and the remotest, most remotely, but as regards ourselves, supermundanely. And the souls, and all the other beings, according to the same rule, have their being, and their well-being; and are, and are well; by having from the Pre-existing their being and their well-being. And in It are both being and well-being; and from It, beginning; and in It, guarded; and to It, terminated. And the prerogatives of being he distributes to the superior beings, which the Oracles call even eternal. But being itself never at any time fails all existing beings. And even self-existent being is from the Pre-existent, and of Him is being, and He is not of being;--and in Him is being, and He is not in being; and being possesses Him, and not He possesses being; and He is both age and beginning, and measure of being; being essentiating Source, and Middle and End, of pre-essence, and being and age and all things. And for this reason, by the Oracles, the veritably Pre-existing is represented under many forms, according to every conception of beings, and the "Was" and the "Is," and the "Will be," and the "Became," and the "Becomes," and the "Will become," are properly sung respecting Him. For all these, to those who think worthily of God, signify by every conception His being superessentially, and Cause in every way of things existing. For He is not this, but not that; nor is He in some way, but not in some other; but He is all things, as Cause of all, and containing and pre-holding in Himself all governments, all controls, of all existing things. And He is above all, as superessentially super-being before all. Wherefore, also, all things are predicated of Him and together, and He is none of them all; of every shape, of every kind, without form, without beauty, anticipating in Himself, beginnings and middles, and ends of things existing, irresistibly and preeminently; and shedding forth without flaw, (the light of) being to all, as beseems a One and super-united Cause. For, if our sun, at the same time that he is one and sheds a uniform light, renews the essences and qualities of sensible creatures, although they are many and various, and nourishes and guards, and perfects and distinguishes, and unites, and fosters, and makes to be productive, and increases, and transforms, and establishes, and makes to grow, and awakens, and gives life to all; and each of the whole, in a manner appropriate to itself, participates in the same and one sun; and the one sun anticipated in himself, uniformly, the causes of the many participants; much more with regard to the Cause of it and of all things, ought we to concede that It first presides over, as beseems One superessential Oneness, all the exemplars, of things existing; since He produces even essences, as beseems the egression from essence. But, we affirm that the exemplars are the methods in God, giving essence to things that be, and pre-existing uniformly, which theology calls predeterminations, and Divine and good wills, which define and produce things existing; according to which (predeterminations) the Superessential both predetermined and brought into existence everything that exists.