*** I could be wrong;)***
Titus 3
"As for a person who stirs up division, after warning him once and then twice, have nothing more to do with him, knowing that such a person is warped and sinful; he is self-condemned."
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Frankly, I don't see Kung renouncing his heresies. Most heretics are so enamored with their view of the god they have created that no amount of reasoning can dissuade them of their views. When a heretic looks in the mirror he sees god.