Laughter is a mental mechanism which enables us to face reality without falling into despondency or delusion. As people who have sunk in apathy seldom bother us by rushing into print, delusion (leaving aside deceit) constitutes the chief obstacle to the progress of our understanding of society, and in this context is usually assumes the form of doctrinairism couched in a mystifying jargon. A sense of humour is the most reliable external indicator of the likelihood of immunity from this folly, and of the ability to appraise social situations realistically.