An Exposition of the Orthodox Faith by Gregory of NyssaChapter 2. Concerning things utterable and things unutterable, and things knowable and thing unknowable.
It is necessary, therefore, that one who wishes to speak or to hear of God should understand clearly that alike in the doctrine of Deity and in that of the Incarnation, neither are all things unutterable nor all utterable; neither all unknowable nor all knowable. But the knowable belongs to one order, and the utterable to another; just as it is one thing to speak and another thing to know. Many of the things relating to God, therefore, that are dimly understood cannot be put into fitting terms, but on things above us we cannot do else than express ourselves according to our limited capacity; as, for instance, when we speak of God we use the terms sleep, and wrath, and regardlessness, hands, too, and feet, and such like expressions.
We, therefore, both know and confess that God is without beginning, without end, eternal and everlasting, uncreated, unchangeable, invariable, simple, uncompounded, incorporeal, invisible, impalpable, uncircumscribed, infinite, incognisable, indefinable, incomprehensible, good, just, maker of all things created, almighty, all-ruling, all-surveying, of all overseer, sovereign, judge; and thatGod is One, that is to say, one essence ; and that He is known , and has His being in three subsistences, in Father, I say, and Son and Holy Spirit; and that the Father and the Son and the Holy Spirit are one in all respects, except in that of not being begotten, that of being begotten, and that of procession; and that the Only-begotten Son and Word of God and God, in His bowels of mercy, for our salvation, by the good pleasure of God and the co-operation of the Holy Spirit, being conceived without seed, was born uncorruptedly of the Holy Virgin and Mother of God, Mary, by the Holy Spirit, and became of her perfect Man; and that the Same is at once perfect God and perfect Man, of two natures, Godhead and Manhood, and in two natures possessing intelligence, will and energy, and freedom, and, in a word, perfect according to the measure and proportion proper to each, at once to the divinity, I say, and to the humanity, yet to one composite person ; and that He suffered hunger and thirst and weariness, and was crucified, and for three days submitted to the experience of death and burial, and ascended to heaven, from which also He came to us, and shall come again. And the Holy Scripture is witness to this and the whole choir of the Saints.
But neither do we know, nor can we tell, what the essence of God is, or how it is in all, or how the Only-begotten Son and God, having emptied Himself, became Man of virgin blood, made by another law contrary to nature, or how He walked with dry feet upon the waters. It is not within our capacity, therefore, to say anything about God or even to think of Him, beyond the things which have been divinely revealed to us, whether by word or by manifestation, by the divine oracles at once of the Old Testament and of the New.