1) Paul does not redefine “one God”
Paul doesn’t split God into multiple persons. He identifies the one God as the Father. This isn’t a footnote—it’s the framework.
2) “One Lord” is not “one God”
In the same breath, Paul confesses one Lord: Jesus the Messiah. Not a second God. Not a co-equal person in a later metaphysical system—God’s appointed Lord, Messiah, and representative.
3) This is the Shema applied, not replaced
Israel’s confession is: YHWH is one (Deut 6:4). The apostles don’t abandon it; they proclaim the Messiah within it. The Father remains the one God. Jesus is confessed as Lord under God.
4) The direction of worship matters
In the apostolic pattern, worship and ultimate source-language terminate in the Father. And the Lordship of Jesus is granted by God (Acts 2:36; Phil 2:9).