CAN ROBOTS LAUGH?

For knowledge based systems knowledge, which is usually given as natural language descriptions, has to be transferred into formal representations. The authors argue that the expressive power of natural language lies partially in the possibility that it can be considered as a rich system of sublanguages. The category of theory morphisms is an adequate mathematical tool to handle the sublanguages of different subfields, different points of references and different levels of abstraction. To prove the claim jokes are analysed and it is shown that in this way a very abstract logical characterisation can be given. The paper tries to answer even the question in the title