The paper deals with the problem of using different languages of writing in the Grand Duchy of Lithuania in the fifteenth to seventeenth centuries. Among them there were: Latin, Polish, Ruthenian, Church Slavonic, Lithuanian, German, Yiddish, Hebrew, Arabic and Greek, written in five alphabets: Latin, Cyrillic, Hebrew, Arabic and Greek. The author noticed that this multi-lingualism and multi-alphabeticism was omitted in Polish studies about the history of literature of the Polish-Lithuanian Commonwealth. He argues that including these two issues in the studies on the Commonwealth's history is crucial to better understand the multi-cultural and multi-ethnic character of this country. One of the main questions of the paper is about the relationship between a script and identity. The author notices that a comparative approach can be especially productive in such research. He examines similar borderland processes in use of writing in medieval and early modern England, Sicily, Malta, Cyprus, Venice, Dubrovnik, Moldova and Andalusia. It is illustrated by a few cases of use of the Cyrillic, Latin and Arabic alphabets. The author draws a comparison between the sixteenth-century literary languages of Spanish Moriscos and Lithuanian Tatars. Both these languages were based on the written version of a vernacular language (Romance and Byelorussian) in the Arabic alphabet.