They knew God, and still they did not honor him as God or give him thanks. Their thinking turned to futility, and their senseless hearts went dark.
In context
19What can be known about God is plain to them; God himself has made it plain. 20Ever since the world was created, his invisible qualities—his eternal power and his divine nature—have been there to be understood in the things he has made. So they have no defense. 21They knew God, and still they did not honor him as God or give him thanks. Their thinking turned to futility, and their senseless hearts went dark. 22Claiming to be wise, they became fools, 23and they traded the glory of the immortal God for images shaped like mortal human beings, or birds, or animals, or reptiles.