Fiction without irony is like a painting without perspective. Irony exposes the incongruities of everyday life--the half-truths, deceptions and self-deceptions that help us all get through the day. Things are never what they seem, and the essence of ironic humor is the lack of fit between life as it is and life as we imagine it should be. We think the world should make sense: It doesn't. We think life should be dignified: It never is. We think life should have a serious purpose. But of course the purpose always turns out to be very silly in the end. Irony is the writer's richest and most inexhaustible humor resource.
The genre of the campus novel, from Kingsley Amis to Richard Russo, is a perfect example. Higher education is meant to be serious business; universities are meant to be serious places. So it's funny when, in Russo's Straight Man, the chair of the English department hides in the ceiling space over the faculty offices to eavesdrop on a meeting between colleagues.
Another reason why irony is such a powerful source of humor is that, as Voltaire observed long ago, life is absurd, but we try to make sense of it. This doomed effort creates some of the best comedy.
David Bouchier in How to Write Funny edited by John B. Kachuba, 2001