There is a limit to human charity," said Lady Outram, trembling all over.

"There is," said Father Brown dryly, "and that is the real difference between human charity and Christian charity. You must forgive me if I was not altogether crushed by your contempt for my uncharitableness today; or by the lectures you read me about pardon for every sinner. For it seems to me that you only pardon the sins that you don't really think sinful. You only forgive criminals when they commit what you don't regard as crimes, but rather as conventions. So you tolerate a conventional duel, just as you tolerate a conventional divorce. You forgive because there isn't anything to be forgiven.

G.K. Chesterton