The author argues that a very significant context for linguistic research on medieval translations is provided by the theory of vernacular literacy which can facilitate new insights into the oldest Polish texts. Its inclusion in the theoretical framework makes it possible to detect that structures deeply rooted in pre-literacy co-existed with structures typical for literate language. The author proposes to imagine the medieval translator as an illiterate man in his vernacular language and a learned one in Latin. The article provides an analysis of structures from Kazanie praskie, Kazania świętokrzyskie and Rozmyślanie przemyskie in the context of theory of literacy.