The Nature of God
To say the nature of God is to say what God is. God named himself, and all that faith confesses of him is held in that name: he is the one who is, being itself. From this single source flows all the rest, that he is one, simple, eternal, without measure, almighty, and that his life is love. We know him by it, without ever exhausting him, for he remains higher than all one can say of him.
He who is
At the burning bush, Moses asks God his name, and God answers by being: “I am who I am.” Exodus 3:14 The Hebrew of this answer, rendered by “I am who I am”, ehyeh asher ehyeh (אֶהְיֶה אֲשֶׁר אֶהְיֶה), gives the very name of God, the one who is. All creatures receive their existence from another: they began, and they could fail to be. God alone is existence in person. He holds his being from nothing and from no one; he is, fully, by himself. There lies the root of all one can say of him: he does not have life, wisdom, power as goods received, he is them. To understand that God is being itself is to hold the key to all his perfections.
One God
From this it follows that there can be only one. Two infinite beings would limit each other and would no longer be infinite; being itself is not divided. There is therefore but one God, and no other beside him. “I am the first and I am the last, and besides me there is no God.” Isaiah 44:6
Without parts
Because he is being itself, God is not composed. A composite thing is made of parts that depend on one another, and what is assembled can be taken apart. God has no parts: he is not made of body and spirit, and his qualities are not added to him. In us, one becomes wise, and wisdom comes to rest upon the person; in God, nothing is added, for he is what he has. His wisdom is his power, which is his goodness, which is his being: one and the same God under various names. When we call him wise, good, just, we divide into words what in him is perfectly one. This is what is called his simplicity: all that he is, he is at once and undivided.
Eternal and immutable
The same principle wills him without change. To change is to gain what one did not have or to lose what one had; God, who is all being, has nothing to acquire and nothing to lose. He is immutable, that is, he does not change. “For I the Lord do not change.” Malachi 3:6 From this it follows too that he is outside time. Time measures change, the before and the after; what does not change does not flow in successive instants. God possesses his whole life at once, with no past gone by nor future lacking: he is eternal. “From everlasting to everlasting, you are God.” Psalm 90:2
Being without limit
Being itself, God has no bounds: he possesses all the perfection of being, excluding none of it. He is infinite. Nothing limits him, so nothing contains him: he is not shut within a place, he is present in every thing, more inward to each than it is to itself, since it is he who makes it be at every instant. “Do I not fill heaven and earth? says the Lord.” Jeremiah 23:24 From this fullness come his power and his knowledge. He is almighty: he can do all that can be, by his will alone. He drew the world from nothing by willing it. “Recognise that God made heaven and earth out of nothing, and that the race of men is the same.” 2 Maccabees 7:28 He is all-knowing: he knows everything without learning anything from outside, by knowing himself as the source of all. The past, the future, the secret of hearts, all is present to him. “All things are naked and laid bare to his eyes.” Hebrews 4:13
Higher than all one says of him
All this language reaches God without ever circumscribing him. God is pure spirit, without body or figure. “God is spirit, and those who worship him must worship in spirit and in truth.” John 4:24 Our words come from created things, and God surpasses them all; we name him after his works, as one guesses the author from the work, knowing that he is all this in an infinitely higher way. “The invisible perfections of God are seen since the creation of the world in his works.” Romans 1:20 This is why one often knows better what he is not than what he is, and every word about him falls short. “Can you fathom the depths of God, attain the perfection of the Almighty?” Job 11:7
Holy, good, love
This fullness of being is fullness of good. God is goodness itself, of which every other good is but a reflection, and the holy one above all, set apart from all evil, before whom the angels veil themselves. “Holy, holy, holy is the Lord; the whole earth is full of his glory.” Isaiah 6:3 This good does not keep itself for itself, it gives itself: God created out of pure generosity and communicates himself without end. At the last, all this fullness receives a name. “God is love.” 1 John 4:8 All the perfections we have named, unity, simplicity, eternity, power, find there their face: being itself is a love that gives itself.
God has revealed that the being he is lives as an exchange of love: the Father, the Son and the Spirit, one God in three Persons. The nature of God is this inexhaustible fullness, which the blessed will contemplate in eternal life without ever exhausting it.