“[Aquinas’s] most vital words on the subject (ST 1 2.3, Utrum Deus sit, “Whether God Exists Anyway”) – the Sed contra – were those that readers of the Bible find God speaking of himself, when asked his ‘name’ by Moses, Exod. 3:14, a question which meant, “What is it that makes him God, so to speak, what is his special feature. His answer is often rendered in English as a manifest tautology (I am who I am, I am he who is, etc.): but it does not really defy translation, being tantamount to saying ‘I am he who will always have been there,’ ayeh asher ayeh, the Hebrew imperfect serving conveniently for future also.”

James Higgins
“St. Thomas’s Pedagogy” (The Heythrop Journal)