That if the Father is one thing, then so too is the Son; and if the Son is such, then so too is the Spirit. That the three are one Spirit of the same glory, essence, and throne.
God is always one. He is always called the one God. We name him as such in our hymns and doxologies: the eternal Father, the co-eternal Son of the Father, and the all-holy Spirit, co-eternal and co-essential with the Father and the Son. This is the co-essential Trinity which is one nature, glory, and origin. This is the one principle of all, the one power, royalty, and omnipotent sovereignty which gives existence to all and creates all from the same throne and in the same glory. When we consider the unity in faith, we worship God as one, and when we profess our faith in the Trinity, we offer praise to the Trinity in the distinct hypostases. This is just as our Lord Jesus Christ has initiated us. He who is one of the three-personed Godhead told us to baptize in the name of the Father and the Son and the Holy Spirit. On another occasion he said: ‘My Father is greater than I.’ This was to show that he is distinct from the Father. And again: ‘I do nothing of myself.’ And yet again: ‘I shall ask the Father and he will send you another comforter, the Spirit of truth which proceeds from the Father.’ In this way, he called the Spirit ‘another.’ It is grace, then, that allows us to understand the absolute unity of Godhead and Dominion in three co-essential hypostases, as well as the permanent identity of the three hypostases within the eternal glory and the inseparable Oneness.
We know that whenever God the Son is wholly named then the Father is wholly present with the Spirit; that when God the Father is wholly praised the Son is wholly there through the Spirit; and that when the Father is wholly confessed and glorified with the Son, then there too is the whole Spirit. This is the mystery which the Spirit teaches us: that the persons are in this way identical in essence and glory, or in other words, the hypostases are united without division or confusion within their one divine nature as the creative cause of all being. Thus, whenever the working of the Spirit lifts us up with him to God the Father through the Son, we stretch out our hands and raise our eyes to him, and say, ‘Our Father who are in heaven.’ Then in that Spirit which confers the understanding, we approach the only Son of the Father to present our prayers to him, and here we say: ‘Only Son, co-eternal Word of God the Father, the only one of the only one, God from God, one without beginning from him who has no beginning, eternal from the eternal, everlasting from everlasting, light from light, life from life, inaccessible from the inaccessible, inconceivable from the inconceivable, inexpressible from the inexpressible, immutable from the immutable, incomprehensible from the incomprehensible, forgive us our sins.’
In the same way we invoke the Holy Spirit by saying this: ‘Holy Spirit, [you] who proceed ineffably from the Father and live in us faithful through the Son, spirit of life and understanding, spirit of holiness and perfection, good spirit and wise, friend of man, gentle and glorious one who refreshes us with food and drink, all merciful giver of light and strength, divine spirit of patience, spirit who gives us joy and gladness, temperance, wisdom, knowledge, and sweetness, you make us forget all our injuries and cares her below, and [bestow upon us] the vision of the good things above. You drive off indolence and take away negligence, putting our curiosity and malice to flight. Spirit, revealer of mysteries, pledge of the kingdom of heaven, source of prophecy, vessel of instruction, remedy of sin and gateway of all repentance, you are like the gatekeeper who shows the way to all who are searching. Spirit of love, peace, faith, and moderation, spirit of desire inspiring desire, come and live in us and stay undivided and inseparable within us. Sanctify our hearts, transform and illumine them, you who are of the same essence and glory as the Son and the Father. You make gods of all who welcome you, wiping out every sin and bringing every virtue with your incoming. You do not have to look beyond yourself to meet all our needs, for you yourself are the substance of all that is good, and those in whom you come to dwell have in their hearts the essence of all good.’
We do not offer our hymn, then, to three gods instead of one, as if we were dividing the indissoluble unity of the whole. No, we worship the Son and the Spirit in the Father, the Spirit and the Father in the Son, and the Father and the Son in the Spirit. We glorify them as one nature of one Godhead in three persons, of the same power and the same essence, self-determinant, all powerful, self-willing, co-eternal, without origin, super-essential, and without confusion or division. We do not imagine that there is one being, then another, and yet a third, one being of such a nature and others of different kinds, for this would be to divide the oneness of the indivisible Godhead and stupidly introduce alien distinctions into his nature. On the contrary, we know the three as one single God, indivisibly divided into the hypostases and united without confusion in the oneness of a single essence. He is wholly one in the hypostases and wholly threefold in the super-essential unity. We must call the same God three in the persons and one in the unity of essence or nature.
It is in this way that the only Son of the Father has showed all of us quite clearly that in all things he is of the same glory, essence, and dominion as the co-essential Father and Spirit, for he says, ‘I and the Father are one.’ And at another time, he showed that the Spirit came forth without any change from this essence when he said: ‘The Spirit of truth proceeds from the Father.’ Just as the waters of a river come from an ‘eye,’ that is, a spring of water, so too God the Spirit proceeds from God the Father. And this is why he also said: ‘God is Spirit and those who worship him must worship in spirit and in truth.’ If, then, the Father is Spirit, it is evident that the Son born from him must equally be Spirit. And if he assumed flesh, he rendered it divine and spiritual. The Holy Spirit is Spirit, for he proceeds from the Father and is given through the Son to us, unworthy though we are. It is not to say that he is sent out or distributed against his will, for in fact, through another in the Trinity, the Son himself, he is fulfilling his own will, which is the good-will of the Father. The Holy Trinity is indivisible in its nature, essence, and will, but because it is [three] hypostases it receives the personal names of Father, Son, and Holy Spirit. Yet there is one God whose name is Trinity, and since he is above every name that can be named and beyond all word or expression, he is transcendent; and since he is no [particularized] thing, he goes beyond the scope of all comprehension.
So, then, understand how the holy Scripture says that the three are one. It is good to take up this same [point] and continue speaking on these things, for the man who knows how to delight in them in a manner pleasing to God finds here a constant source of joy, and the divine word sanctifies the feelings of his soul. It is said: ‘God is Spirit,’ and as we have said, the Son too must be [Spirit]. So if God is Spirit and the Lord is the Spirit, and if the divine Scriptures call the Lord ‘Spirit,’ then it follows that God is one Spirit known in three persons or hypostases. This was why the Son spoke of the ‘One,’ in order to make us understand. But in all there is the same power, the same throne, the same nature, and the same essence. If the persons are called one single Spirit in this way, it is in order that you should not suppose that there is any inequality in the three persons of the Trinity, no superiority or inferiority. There is no division of any sort that can be rightly applied. The names do not signify this, but are there as a means of teaching us of the very existence of the hypostases and persons. If we are so taught and sufficiently initiated in the affairs of God, we should not be so indiscreet as to inquire any further. By faith we receive this much alone. Keep to it, be assured, and profess that the things above us are completely beyond our comprehension.
However, we will initiate you into this fact as well: that God is light, a light infinite and incomprehensible, for then you will know about the properties of the divine nature, how God and all that is of God, from God, and within God, is one light, worshipped in each of the hypostases and perceived in all the qualities and gifts of God. Everything to do with God is light, and [this light] is common to all the persons, divided between them indivisibly. But if for your sake I may speak of the indivisible as if it were divided: the Father is light, the Son is light, the Holy Spirit is light; one single light as they are simple, non-composite, timeless, eternal, and possessed of the same honor and glory. All that comes from him is light, and is given to us as arising from the light. The light is life. The light is immortality. The light is the source of life. The light is living water, charity, peace, truth, and the door of the kingdom of heaven. The light is the very kingdom itself. The light is the bridal chamber, the bridal couch, paradise, and all the bliss of paradise. It is the land of the gentle, the crowns of life, and the very garments of the saints. The light is Jesus Christ, the Saviour and King of the universe. The bread of his sinless flesh is light. The chalice of his precious blood is light. His resurrection is light. His face is light. His hand, his finger, his mouth, his eyes, all are light. The Lord is light, and his voice is as light from light. Light is the comforter, the pearl, the seed of mustard, the true vine, the leaven, hope, and faith—all are light.
So all this and everything else you might hear from the apostles and prophets about the inexpressible and super-essential deity you must understand, I beg you, as being by essence the one principle which is above all principles, adored in the unity of the threefold light. For God is one in Father, Son, and Holy Spirit. He is light inaccessible, pre-existing the ages. He bears all these titles and can be designated by all such terms we use and many others besides. And these are not just names, but energies. I have been taught this by men who have learned it from their own experience, men who have been securely taught about the good things inherent in the infinitely good God from their own contemplation. Indeed, I will show you in passing some of the other ‘lights’ applicable to God: his goodness is light; his compassion is light; his mercy, his embrace, his watchful care are light. His sceptre is light, his crook, and his consolation.
Now the majority of these terms, in fact all of them, can be applied to us, but then they apply only in a human way. To him they apply as God. Nor will I hesitate in repeating them for you one by one: God is called Father, and most men are called fathers, too. The divine Christ is the Son of God, and so too are we sons of men. The all-holy Spirit is the Spirit of God, and our souls, too, are called spirit. God is life, and we too are said to be alive. God is love, and mutual love exists even between great sinners. But does this mean that we equate God with human love? No, this is blasphemy! Could we even claim that the peace we men experience is ‘that peace which passes all understanding’? Of course not, for the peace we know is usually a matter of avoiding disputes and wrangles. Then does God’s truth simply amount to the fact that he does not lie to anyone? Again, not at all. The words of men are ephemeral and pass away, but the word of God is something alive and real and active. It is, in fact, true God, God and truth itself. It transcends all human thought and speech. It is unchangeable, unalterable, subsisting in its own life.
And likewise the water which we see is not that ‘living water,’ nor is our bread like that ‘living bread’; no, as I have said previously, all these things are light, and God is the one single light. The man who shares in this thereby shares in all the good things we have spoken about, in both senses. Such a man becomes gentle and humble, for these things, along with all the rest, are also light. In short, the man who has this light has, with this light, all other things as well. In addition to all this, God could also be called the Watchman, for when he enters to live in a man, he wakens up his soul to the good, and for that soul he becomes every good. And when it has God indwelling, it lacks no good thing, but is always full to overflowing with all the breath-taking gifts of God. It is at home with the ranks of heavenly powers and shares in their joy. Let all of us, then, strive to win and enjoy these riches by the grace and kindness of our Lord Jesus Christ, to whom be glory and dominion with the Father and the Holy Spirit, now and forever, and through the ages of ages. Amen.