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.
God revealed himself to Moses as the living God, “the God of Abraham, the God of Isaac, the God of Jacob” (Exodus 3:6). God also revealed to Moses his mysterious name “I Am Who I Am (YHWH)”. Already in Old Testament times this ineffable name of God was replaced by the divine title Lord. Thus in the New Testament, Jesus who was called Lord is seen as true God.
Since creatures have received everything they are and have from God, only God in himself is the fullness of being and of every perfection. God is “He who is” without origin and without end. Jesus also reveals that he bears the divine name “I Am” (John 8:28).
In revealing his name, God makes known the riches contained in the ineffable mystery of his being. He alone is from everlasting to everlasting. He is the One who transcends the world and history. It is he who made heaven and earth. He is the faithful God, always close to his people, in order to save them. He is the highest holiness, “rich in mercy” (Ephesians 2:4), always ready to forgive. He is the One who is spiritual, transcendent, omnipotent, eternal, personal, and perfect. He is truth and love.
“God is the infinitely perfect being who is the most Holy Trinity.” (Saint Turibius of Montenegro)
God is Truth itself and as such he can neither deceive nor be deceived. He is “light, and in him there is no darkness” (1 John 1:5). The eternal Son of God, the incarnation of wisdom, was sent into the world “to bear witness to the Truth” (John 18:37).
God revealed himself to Israel as the One who has a stronger love than that of parents for their children or of husbands and wives for their spouses. God in himself “is love” (1 John 4: 8.16), who gives himself completely and gratuitously, who “so loved the world that he gave his only Son so that the world might be saved through him” (John 3:16-17). By sending his Son and the Holy Spirit, God reveals that he himself is an eternal exchange of love.
To believe in the one and only God involves coming to know his greatness and majesty. It involves living in thanksgiving and trusting always in him, even in adversity. It involves knowing the unity and true dignity of all human beings, created in his image. It involves making good use of the things which he has created.