The fifth and most profound difference lies in the way the two traditions understood the key phrase in which God identifies himself to Moses at the burning bush. ‘Who are you?’ asks Moses. God replies, cryptically, Ehyeh asher ehyeh. This was translated into Greek as ego eimi ho on, and into Latin as ego sum qui sum, meaning ‘I am who I am’, or ‘I am he who is’. The early and medieval Christian theologians all understood the phrase to be speaking about ontology, the metaphysical nature of God’s existence. It meant that he was ‘Being-itself, timeless, immutable, incorporeal, understood as the subsisting act of all existing’. Augustine defines God as that which does not change and cannot change. Aquinas, continuing the same tradition, reads the Exodus formula as saying that God is ‘true being, that is being that is eternal, immutable, simple, self-sufficient, and the cause and principal of every creature’.
Sacks, Jonathan (2012-09-11). The Great Partnership: Science, Religion, and the Search for Meaning (p. 64). Knopf Doubleday Publishing Group. Kindle Edition.