I Believe...Catechism drills down into the Creed

198 Our profession of faith begins with God, for God is the First and the Last, the beginning and the end of everything. The Credo begins with God the Father, for the Father is the first divine person of the Most Holy Trinity; our Creed begins with the creation of heaven and earth, for creation is the beginning and the foundation of all God's works.

Article1:"I believe in God the Father almighty, Creator of heaven and earth" (199 - 421)

Paragraph1:I Believe in God (199 - 231)

199 "I believe in God": this first affirmation of the Apostles' Creed is also the most fundamental. The whole Creed speaks of God, and when it also speaks of man and of the world it does so in relation to God. The other articles of the Creed all depend on the first, just as the remaining Commandments make the first explicit. The other articles help us to know God better as he revealed himself progressively to men. "The faithful first profess their belief in God."

I. "I BELIEVE IN ONE GOD"

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."

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." 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.'"

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". At the same time Jesus gives us to understand that he himself is "the Lord". 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.