Because, when they knew God, they glorified him not as God, neither were thankful; but became vain in their imaginations, and their foolish hearts were darkened.
All Commentaries on Romans 1:21 Go To Romans 1
Gennadius of Constantinople
AD 471
The pagans knew that there was a God, and it is clear that they did not receive judgment because of this. For it was not for want of knowledge that they were condemned, but the opposite. For each one glorified God in the sense that whatever he thought God was, that he served. Thus they corrupted the whole matter by their peculiar and mistaken ideas. They abandoned God’s way of knowing him and preferred their own, falling into the deepest imbecility, outdoing themselves in their socalled wisdom by adding to their foolishness, descending to the worship of reptiles and inanimate objects. .