Bailey, fortunately, disarms the reader at the outset by announcing that he's always been cocksure about everything. Please forgive. He then launches his all-encompassing--and quite original--theory of humor. Disconcertingly, it bears a resemblance to Robert Ardrey's theory of aggression, being similarly grounded in ethology, more specifically in the behavior of Og and other prehominids sighting a tiger. A tiger? Humor, all humor, according to Bailey, depends on an opposite or an exaggeration which is a kind of modified opposite, as an oblong is a modified square. A joke is like a tiger because it ""makes a violent attack on the reader's judgment or knowledge"" and the subconscious mind, always alert to danger, leaps to defend Og. Laughter, ""a modification of the noise that used to frighten tigers away,"" is vocal and triumphant because it is colored by ""a feeling of deliverance from danger"" (20th-century dangers are mostly attacks on the intellect or ego). Bailey, former humor editor of the old Saturday Evening Post, works it out through puns, humorous verse, caricature, satire, and plays on words--with a lot of help from Lewis Carroll, Stephen Leacock, Beerbohm, Wodehouse, W. S. Gilbert, et al. He develops his own ""humor structure"" and doesn't give a rat's ass about Freud's or Bergson's or anyone else's theories. It might not pass muster with Woody Allen or Peter Sellers, but it may tickle your fancy just the same.