Matthew Levering, Scripture and Metaphysics: Aquinas and the Renewal of Trinitarian Theology, (Oxford: Blackwell) 2004, p. 47-74.
Synopsis: Thomas’ division of the treatise on God in the Summa Theologiae into a treatise on the divine essence and a treatise on the divine persons observes the fact that neither the revealed divine name “YHWH” nor “Father, Son and Holy Spirit” (which are his starting points in each treatise respectively) can be reduced to the other. It avoids the supersessionist tendency in Trinitarian theology whereby the one God of the Old Covenant is superseded by the revelation of the Trinity. In other words, the one God revealed to Moses on Mt. Sinai by a name both existential (“he who is”) and personal (“has sent me to you”) is the God of Israel and the Father, Son and Holy Spirit and yet the absence of the latter name (as was the case in Israel prior to the New Testament) does not render the former less personal. Thus a treatise on the divine name YHWH is (1) not a purely philosophical analysis since the existential character of the name is derived from the sacred text and (2) no more an impersonal abstraction from the living God than the contemplative doctrine of Moses and the Prophets centered on the unity of God revealed in the divine name YHWH.
“As the Torah makes clear, both Moses’ contemplative life and his corresponding active life revolve around his mission to separate Israel from the idolatry of the nations. This intimate connection of his divinely ordained mission with the (revealed) truth about God [i.e. unity] suggests, as Aquinas holds, that Moses, in comparison with the patriarchs, “was more fully instructed in the unity of the Divine essence.” The importance of Moses’ receiving the name “I am who am” at the very moment of his receiving his active mission cannot be overemphasized. Agreeing with traditional Jewish understanding of the relationship of Moses to the later prophets, Aquinas states that “all the other revelations to the prophets were founded” upon the fundamental revelation to Moses. He argues that the Old Testament, which for him is entirely a collection of prophetic books, centers upon the Mosaic revelation of God’s simplicity. Thus, the Mosaic Law has its own integrity “by withdrawing men from idolatrous worship” and including “them in the worship of one God by Whom the human race was to be saved by Christ.” The written law reveals the necessity of apprehending God’s simple being in order to attain to the end – God himself – that God has ordained for rational creatures. Knowing God as sheer infinite “being” does not involve capturing God in a concept; on the contrary, a proper apprehension of God as “I am who am” destroys all conceptual idolatries that seek to place God within a finite creaturely category.” (66-67)
“Rather than bypassing God’s eternal identity as YHWH, Aquinas integrates his metaphysical reflection on the name “I am who am” into a complex account of YHWH, Moses, the Mosaic Law, and the relationship of Christians to the contemplative life enjoyed by Moses and sustained, in its critique of idolatry, by the Mosaic Law. Through Moses and Israel, God teaches humankind about the being and simplicity of God. For Aquinas, the divine name given to Moses fully displays the divine unity: “Hear, O Israel, the Lord our God is one Lord” (Deuteronomy 6:4). Understood in this way, contemplative knowledge of God involves a double movement. This movement begins with contemplating YHWH, God known as one and as sheer infinite being, who is not a philosophical abstraction but rather the personal God. In a second movement, this God is contemplated in his threeness [“redoublement”, Gilles Emery].” (71-72)