The central topic of this proseminar will be to challenge a fairly widespread conviction that languages differ beyond limits and in unpredictable ways. Under this view, logically, there is no such a thing as an ‘impossible language’. Evans and Levinson (2009) define this point fairly conspicuously: “languages differ so fundamentally from one another at every level of description (sound, grammar, lexicon, meaning) that it is very hard to find any single structural property they share”. During the proseminar this claim will be confronted with arguments by different authors and examples from distinct languages. The  issue of language diversity will be addressed from a variety of viewpoints, and some of the questions to raise will be: Why is there language diversity at all?  How is it manifested? Are there language universals and the universal grammar?