By St. Gregory the Theologian
(Oration 38, On the Theophany, 8-10)
But when I say God, I mean Father, Son, and Holy Spirit. For Godhead is neither diffused beyond these, so as to bring in a mob of gods; nor yet is it bounded by a smaller compass than these, so as to condemn us for a poverty-stricken conception of Deity; either Judaizing to save the Monarchia, or falling into heathenism by the multitude of our gods. For the evil on either side is the same, though found in contrary directions. This then is the Holy of Holies, which is hidden even from the Seraphim, and is glorified with a thrice repeated Holy, meeting in one ascription of the title Lord and God, as one of our predecessors has most beautifully and loftily pointed out.
But since this movement of self-contemplation alone could not satisfy Goodness, but Good must be poured out and go forth beyond Itself to multiply the objects of Its beneficence, for this was essential to the highest Goodness, He first conceived the Heavenly and Angelic Powers. And this conception was a work fulfilled by His Word, and perfected by His Spirit. And so the secondary Splendors came into being, as the Ministers of the Primary Splendor; whether we are to conceive of them as intelligent Spirits, or as Fire of an immaterial and incorruptible kind, or as some other nature approaching this as near as may be. I should like to say that they were incapable of movement in the direction of evil, and susceptible only of the movement of good, as being about God, and illumined with the first rays from God — for earthly beings have but the second illumination; but I am obliged to stop short of saying that, and to conceive and speak of them only as difficult to move because of him, who for his splendor was called Lucifer, but became and is called Darkness through his pride; and the apostate hosts who are subject to him, creators of evil by their revolt against good and our inciters.
Thus, then, and for these reasons, He gave being to the world of thought, as far as I can reason upon these matters, and estimate great things in my own poor language. Then when His first creation was in good order, He conceives a second world, material and visible; and this a system and compound of earth and sky, and all that is in the midst of them — an admirable creation indeed, when we look at the fair form of every part, but yet more worthy of admiration when we consider the harmony and the unison of the whole, and how each part fits in with every other, in fair order, and all with the whole, tending to the perfect completion of the world as a Unit.