Euthymius Zigabenus, Panoplia Dogmatica; Theodoretus, Historia Religiosa

If then, everyone should confess all things that exist, and before the race, both intelligible and sensible; soulish, and changeable; for those whose being began from change, these will entirely be subject to change; either being corrupted, as those things being altered; or being altered according to volition, as angels; and souls; everywhere the progress toward evil, and the movement toward good; but God is motionless, entirely and immutable; for those whose being is contrary, the account of how they are is also contrary; otherwise, not only do the creations viewed proclaim the creator, but also the order and harmony and preservation of these. For how could the natures of the elements, being from the opposite, have come together into the completion of one world, without someone reconciling and holding them together; how would all things also preserve the order from the beginning, if there were not one governing and conducting them.

Syllogistic proof of the same, that there is one God:

A rubricated ornamental initial O in red ink. God Theos is perfect in all things; therefore, in those things viewed in many gods, it is necessary that difference be viewed in the many. If there is no difference in them, the one who is perfect in all things, this is the true God; but everyone who falls short of the perfect; either according to likeness; or according to power or wisdom or altogether according to something, would not be God. And how will the unlimited be preserved in many gods; for where both are, the other would not be; but it is necessary for God to be unlimited and filling all things and limiting them in Himself; otherwise, also how will the world be constituted and governed by many; with the difference opposing harmony.

Syllogistic proof of the same, concerning the Word and the Spirit:

A rubricated ornamental initial O in red ink. God Theos being perfect, is not without a word; but having a word, He does not have it as insubstantial; nor beginning to be, nor ceasing; for He was never without a word; but being, He always has His own Word; born from Him, and remaining in Him; and living; and perfect; and not a word only in thought; for if the being is different, the word of this is also different; as our word; born from the mind, it is neither entirely the same as the mind; nor altogether different; for being from the mind, it is another beside it; but manifesting the mind itself, it is no longer entirely different beside it, but being one according to the nature, it is different in the underlying subject. So also the Word of God Theou; which is the Son Hyios; by subsisting in itself, it is divided from that one; but by having the birth from him; it shows all these in itself which are observed concerning God Theon; it is one toward Him according to the nature.