Franciszek Ksawery Bohusz (1746–1820) was a philosopher, theologist, Jesuit, political activist, participant of the Kościuszko Uprising, member of the Warsaw Society of Friends of Science, honorary member of the Vilnius University, translator and publisher of the Napoleon Code, who was also the author of the thesis On the Origins of the Lithuanian Nation and Language (1808). The thesis was written in an effort to save from forgetting the traditions of the people whose language, as the author noted, gradually “diminished” and “faded” at the beginning of the nineteenth century, being crowded out by Polish which was used in various areas of everyday life. Bohusz’s work turned out to be a significant voice, a testament which raised interest of many Lithuanian culture researchers. It contributed to the longterm study of the history of the Lithuanian nation and language by numerous Vilnius University professors and students.