Hilary of Poitiers

While therefore I was giving serious thought to these and many other similar problems, I chanced upon those books which according to Jewish tradition were written by Moses and the prophets. In them I found the testimony of God the Creator about himself expressed in the following manner: “I am who I am,” and again, “Thus shall you say to the children of Israel: He who is, has sent me to you.” I was filled with admiration at such a clear definition of God, which spoke of the incomprehensible nature in language most suitable to our human understanding. It is known that there is nothing more characteristic of God than to be, because that itself which is does not belong to those things which will one day end or to those which had a beginning. But that which combines eternity with the power of unending happiness could never not have been, nor is it possible that one day it will not be, because what is divine is not liable to destruction, nor does it have a beginning. And since the eternity of God will not be untrue to itself in anything, he has revealed to us in a fitting manner this fact alone, that he is, in order to render testimony to his everlasting eternity.