The verses they cite — read them in context.
Deuteronomy 6:4
"The LORD our God, the LORD is one."
John 17:3
"You, the only true God, and Jesus Christ whom you have sent."
1 Corinthians 8:6
"One God, the Father... and one Lord, Jesus Christ."
Read in context — do these verses say God is only one person, or that there is only one God?
Debate doesn’t change minds. If you find yourself arguing, pivot to telling your story of how Jesus changed you, saved you, and protected you.
Usually the first objection raised — closely tied to who Jesus is.
The Trinity is the biblical teaching that there is one God who eternally exists as three distinct persons: Father, Son, and Holy Spirit. Not three gods, and not one person wearing three masks — one Being, three persons. The word isn't in the Bible, but neither is "theocracy" or "Governing Body." The teaching is.
Read in context — do these verses say God is only one person, or that there is only one God?
If all three are called God yet act as distinct persons, what does that tell you about who God really is?