This treatise presents and defends a new theory of humour, one designed to cover all examples of all types and to provide the foundations for a full account of the global phenomenon. Incongruity theory and the new theory are contrary in the strict logical sense of the term. Hence a determined effort is made to demonstrate that incogruity theory in general, in all its forms, fails. Among the topics covered are: the anti-essentialist approach; the concept of a humour process and that of the basic humour process; the subjective character of humour; the laughter of humour, relaxation and pleasure; humour and organic evolution; elementary incongruity theory; incongruity-and-resolution theory; the fantasy element in humour and "funny incongruity"; the notion of "local logic" in humour; the precise locus of the mystery of humour; the remarkable appeal of incongruity theory; psychological experiments in incongruity theory; Kant"s and Koestler"s theories of humour; and the current state of research into the basic humour process.