The Manichean Problem

But [the Manicheans] believe as they do because they are ignorant how to interpret any passage except literally. If this is not so, let them show how it is just, in a literal sense, for the sins of the parents to be visited on the heads of the children, and on the children's children after them, to the third and fourth generation? We, however, do not understand such sayings in a literal sense, but as Ezekiel taught when he uttered his well-known "proverb", we inquire what is the inner meaning of the proverb.

-Origin