37. Why does one profess belief that there is only one God?

37. Why does one profess belief that there is only one God?)

(Comp 37) Belief in the one God is professed because he has revealed himself to the people of Israel as the only One when he said, “Hear, O Israel, the Lord our God is one Lord” (Deuteronomy 6:4) and “there is no other” (Isaiah 45:22). Jesus himself confirmed that God is “the one Lord” (Mark 12:29). To confess that Jesus and the Holy Spirit are also God and Lord does not introduce any division into the one God.

“In Brief”

(CCC 228) "Hear, O Israel, the LORD our God is one LORD..." (Dt 6:4; Mk 12:29). "The supreme being must be unique, without equal… If God is not one, he is not God" (Tertullian, Adv. Marc., 1, 3, 5: PL 2, 274).

To deepen and explain

(CCC 200) These are the words with which the Niceno-Constantinopolitan Creed begins. The confession of God's oneness, which has its roots in the divine revelation of the Old Covenant, is inseparable from the profession of God's existence and is equally fundamental. God is unique; there is only one God: "The Christian faith confesses that God is one in nature, substance and essence" (Roman Catechism, I, 2, 2). (CCC 201) To Israel, his chosen, God revealed himself as the only One: "Hear, O Israel: the Lord our God is one Lord; and you shall love the Lord your God with all your heart, and with all your soul, and with all your might" (Dt 6:45). Through the prophets, God calls Israel and all nations to turn to him, the one and only God: "Turn to me and be saved, all the ends of the earth! For I am God, and there is no other…. To me every knee shall bow, every tongue shall swear. 'Only in the LORD, it shall be said of me, are righteousness and strength'" (Isa 45:22-24; cf. Phil 2:10-11).

On reflection

(CCC 202) Jesus himself affirms that God is "the one Lord" whom you must love "with all your heart, and with all your soul, and with all your mind, and with all your strength" (Mk 12:29-30). At the same time Jesus gives us to understand that he himself is "the Lord" (Cf. Mk 12:35-37). To confess that Jesus is Lord is distinctive of Christian faith. This is not contrary to belief in the One God. Nor does believing in the Holy Spirit as "Lord and giver of life" introduce any division into the One God: We firmly believe and confess without reservation that there is only one true God, eternal infinite (immensus) and unchangeable, incomprehensible, almighty and ineffable, the Father and the Son and the Holy Spirit; three persons indeed, but one essence, substance or nature entirely simple (Lateran Council IV: DS 800).

(Next question: With what name does God reveal Himself?)