Good manners.

Bhikkhus, these two morally good things protect the world. What two? Shame and regret. Bhikkhus, if these two morally good things did not protect the world, people would not know the mother or the stepmother or the aunt, or the teacher's wife, as the teacher's wife. There is a difference in the world unlike among goats, fowl, pigs, dogs, and foxes. Since these two morally good things protect the world, people know the mother, the stepmother, the aunt, or the teacher's wife as the teacher's wife. This is the nineth.