EN
The article is devoted to social concepts of the Hussite thinker Peter Chelcicky (b. around 1380 – d. before 1460). The main attention is focused on his image of a world turned upside down, in which falsehood dominates the truth and nearly everything is the reverse of what it seems to be. Although the fundamental features of this concept were commonly present in medieval thinking, Chelcicky did expand them greatly and they became the starting point of his revolutionary sociological thoughts and his devastating critique of society. This study also deals with the issue of how his notion of a world turned upside down influenced the language and vocabulary of Chelcicky’s writings.