When a thoughtful human being has overcome incentives to vice and is aware of having done his bitter duty, he finds himself in a state that could be called happiness, a state of contentment and peace of mind in which virtue is its own reward.
That is not the best sermon which makes the hearers go away talking to one another and praising the speaker, but which makes them go away thoughtful and serious, and hastening to be alone.
That is a simple rule, and easy to remember. When I, a thoughtful and unblessed Presbyterian, examine the Koran, I know that beyond any question every Mohammedan is insane; not in all things, but in religious matters.