People in political society cannot help but make judgments about what is good, and seek ways to make sure those things are done in common.
Cultural Christianity never saved anyone, and to the degree that it covered over sin and wickedness, God hated it, and we ought to condemn it. But cultural Christianity, however imperfect, was and is a manifestation of the Tao. In that sense, it tills the soil to prepare it for the seed. As Lewis said, it gives us something to work on and to work with. It teaches us through laws and customs and cultural practices the reality of the Tao, of God’s moral order. So, cultural Christianity never saved anyone, but it did give many a sense of sin and guilt, which prepared them for the good news of Jesus.