Commentaria in Exodum
St. Thomas, part 1, Question 10, and there the Theologians distinguish three things: eternity, aevum and time, thus. First, that time is the measure of the duration of men and of corruptible things; aevum the measure of the duration of angels; eternity the duration proper to God. Secondly, that time has beginning and end; aevum has beginning but not end; and eternity has neither beginning nor end. Thirdly, that time is the measure of those things which actually corrupt and perish; aevum is the measure of incorruptible things, which yet can absolutely cease and perish; eternity belongs to God, who cannot cease, vary or change. Fourthly, that time has succession; eternity permanence; aevum partly succession, partly permanence. For although an angel naturally in his aevum is always stable and like himself, yet he depends continually on God, and by an influx continuously continued is sustained by God, which God can withdraw at any moment: and if he withdrew it, the angel, like any other creature, would at once vanish, and fall back into the nothing from which he came.
God is therefore the author and Lord of eternity, of times and of all ages; and of this his blessed eternity he makes both angels and holy men partakers. He is therefore to be worshipped, loved and feared by us. So St. Fructuosus the Martyr, compelled by the Emperor Gallienus to venerate idols, otherwise to be punished with death, answered: “I will not sacrifice to the gods of Gallienus, but I worship and venerate the eternal God, and the Creator of Caesar himself.” Alluding to which Prudentius sings thus:
It was commanded by the mouth of Caesar Gallienus, that what the prince worships we all should worship; I worship the eternal prince, the Maker of days and Lord of Gallienus.
Fourth, St. Jerome on chap. 3 to the Ephesians: “I am who am,” that is, I alone am, because I alone have being from myself; I alone am he who am not produced or begotten by anyone; but the rest are not of themselves and by their nature, but have being from my will, as much, in what manner and as long as I will.
Fifth, “I am who am,” because whatever is in me is not an accident, but is my being, or the same with my essence; for my goodness, wisdom, power are the same with my essence. Whence St. Bernard, book 5 to Eugene: “God,” he says, “loves as charity, knows as truth, sits as equity, rules as majesty, governs as principle, guards as salvation, works as virtue, reveals as light, assists as piety: all which things angels also do, and we do; but in a far inferior way, not indeed by the good that we are, but by that which we participate; but God by this very thing that he is, for he says: I am who am.”
Sixth, “I am who am,” that is, I am most pure and simplest act; for if I were composed, I should be posterior to the parts composing me, and from them should have my being, whereas now I have my being from myself alone.
Seventh, “I am who am,” that is, I have being most universal, unlimited and infinite; for since I have being from myself, my being could not be determined for me: hence I am being itself subsisting, incomprehensible, unnameable and infinite.
Eighth, “I am who am,” that is, I am the cause of all being which created things participate; for what is such of itself and by itself is the cause of those things that are such by participation; from that uncreated and immense being of God, therefore, it follows that he can do all things. This is what Boethius sings, book 3 On Consolation, metre 6:
O thou who governest the world by perpetual reason, Creator of earth and heaven, who from the age biddest time go forth, and abiding stable givest all things to be moved; whom no external causes drove to fashion the work of fluctuating matter, but the form of the highest good, implanted, free from envy.
and Horace, book 1 Odes:
Who rules the affairs of men and of gods, who the sea and lands, and the world with its changing seasons.
Ninth, “I am who am,” that is, I am one, who have being from myself. Rightly therefore said Job chap. 23: “He alone is;” for if there were any other, having a like independent and infinite being, he would be another God, having another nature, another independent and immense being, and consequently our true and one God would not have the nature nor the being of that other God; and so would not have all being, and consequently would not be God. Hence St. Dionysius, chap. 5 On the Divine Names, teaches that God is called being rather than anything else, for nine reasons. First, because being comes first to any thing, and departs last from it; second, because being is most intimate to any thing; third, it is most independent; fourth, most necessary; fifth, most universal; sixth, most simple; seventh, in a certain way infinite; eighth, all other things are a participation of being and of existence, but being is a participation of none; ninth, it is most perfect, because eminently and virtually it contains the other perfections.
From which you may rightly gather that the proper name of God is: “I am who am.” For it signifies the very essence of God, namely an immense ocean of being, from which, in our way of conceiving (for in itself, namely in the very essence of God, all things are one most simple thing), all the attributes of God flow in their order, as from the essence of angel, man, horse, all his endowments and properties flow in their order. Therefore because God is the very being, or fullness of being, hence it necessarily follows that he is one, most perfect, most simple, infinite, independent, most universal, immutable, eternal, omniscient, omnipotent, holy, best, most provident, the cause of all things, not only existing and future, but also possible. For a thing is therefore possible because God can make it, and communicate to it his being, or because the being of God can be participated by it.
For the root of the possibility of a creature is in God, not in the creature itself. For this root is the imitation, commendation and participation of the divine essence, namely that the divine essence can communicate itself to a creature in such a manner, and be participated by it in such a manner, as that which contains it eminently in itself. For if the essence of God cannot be participated in such a manner, the thing is plainly impossible. For what God cannot make, or to which he cannot communicate himself, that is altogether impossible: so man is possible, because the essence of God is participable by man. And God has a practical idea of man in his essence, according to which he can form him and communicate to him his being; but a chimera is impossible, because it cannot participate the essence of God, nor has God an idea of it, according to which he might form it and communicate to it his being; because namely the essence of God does not contain the chimera in itself, either formally or eminently. Wherefore some Theologians set “I am who am” as the principle, nay the sum and compendium, of all Theology.
Note: As the name of God is to be, so on the contrary the name of creatures is not to be; so that if man, stone, angel were asked: Who art thou? what art thou called? he could and should answer: My name is Not-being; I am not called, I am not; and that first, because every created thing, before it was created, had an eternal not-being. Secondly, if it is corruptible, it will have again an eternal not-being; but if incorruptible, as an angel is, it can always have not-being, because its being is in the power of God freely conserving it, and able every moment to annihilate it. Thirdly, because while it is, it is variable and mutable, and so has not-being mixed in; for in every change some reason of its not-being is included. Fourthly, because every created thing, says Plato in the Theaetetus, has more of not-being than of being, e.g. a man has only the being of a man, but has not the being of heaven, earth, stone, angel and of all other things. Therefore man has only one being, and innumerable not-beings. How wise is he who knows himself and his not-being! So St. John the Baptist, asked: Art thou Christ? art thou the Prophet? answered: I am not.
Men boast, and wish to be what they are not, and say: I am rich, I am noble, I am wise; but those who are humble and wise, who know themselves and God, say: God is good, is rich, is wise, is holy, I am not; and by this they deserve to be made partakers of divine wisdom, goodness, holiness, and of all good and being. Wherefore Christ the Lord appearing to Blessed Catherine of Siena said to her: “Dost thou know, daughter, who I am, who thou art? thou shalt be blessed, if thou know it. I am he who am; thou art she who art not.” And again: “Daughter, think of me, and I will think of thee, and always have care of thee;” she did this, humbling herself and annihilating herself and dwelling in her nothing: and so she was raised to the immense ocean of divine being and of all his perfections, and was wholly kindled to his love and continual praise.
This same “I am not” Blessed Henry Suso treats finely and fully, serm. 2. “God,” says St. Basil, “made the world: as good, useful; as wise, most beautiful; as powerful, greatest. If we have learned these things, we shall know ourselves, we shall know God, we shall adore the Maker, serve the Lord, glorify the Father, love the Nourisher, reverence the Benefactor, never cease to worship the author of the present and the future life.”
The Gentiles seem to have drawn and learned this notion and theology of God from the Hebrews. Eugubinus reports that in the temples of the Egyptians this emblem of God was inscribed: “I am what was, what is, and what shall be; my veil no one has ever uncovered.” So also Plutarch, book On Isis, relates that in Egypt the statue of Sais, which is of Minerva, whom he thinks the same as Isis, has an inscription of this kind: “I am the all that was, and is, and shall be; and my flaming robe no mortal has ever opened.” See Goropius in Hermathena, book 5, fol. 106, where he contends from Plutarch that by Isis divine Wisdom is understood, and that the name Isis sounds the same as “is, is.” Thales also, asked what God was, answered: “That which always is, having neither beginning nor end.”