Flippancy is the best [kind of joke] of all. In the first place it is very economical. Only a clever human can make a real joke about virtue, or indeed about anything else; any of them can be trained to talk as if virtue were funny. ...

If prolonged, the habit of flippancy builds up around a man the finest armourplating against the Enemy [God] that I know, and it is quite free from the dangers inherent in the other sources of laughter. It is a thousand miles away from joy: it deadens, instead of sharpening, the intellect; and it excites no affection between those who practice it.

-- Your affectionate uncle SCREWTAPE