While the Greek philosophers were wondering what place to assign to their gods in a philosophically intelligible world, the Jews had already found the God who was to provide philosophy with an answer to its own question. Not a God imagined by poets or discovered by any thinker as an ultimate answer to his metaphysical problems, but one who had revealed Himself to the Jews, told them His name, and explained to them His nature, in so far at least as His nature can be understood by men.
The first character of the Jewish God was His unicity : “Hear, O Israel: The Lord our God is one Lord” (Deuteronomy 6:4). Impossible to achieve a more far-reaching revolution is fewer words or in a simpler way. When Moses made this statement, he was not formulating any metaphysical principle to be later supported by rational justification. Moses was simply speaking as an inspired prophet and defining for the benefit of the Jews what was the henceforth to be the sole object of their worship.
Yet, essentially, religious as it was, this statement contained the seed of a momentous philosophical revolution, in the sense at least, that should any philosopher, speculating at any time about the first principle and cause of the world, hold the Jewish God to be the true God, he would be necessarily be driven to identify his supreme philosophical cause with God. In other words, whereas the difficulty was, for a Greek philosopher, to fit a plurality of gods into a reality which he conceived as one, any follower of the Jewish God would know at once that, whatever the nature of reality itself may be said to be, its religious principle must of necessity coincide with its philosophical principle. Each of them being one, they are bound to be the same and to provide men with one and the same explanation of the world.
Etienne Gilson, God and Philosophy (Yale Nota Bene: 1941) pp. 38-39