ENThe article critically assesses the theory of communicative networks and its applicability in the study of multilingualism as found in the Grand Duchy of Lithuania (GDL). The author analyzes foundations for postulating the existence of a speech community in the GDL and adduces counterarguments against viewing this community as a linguistic alliance of the Balkan type. The article offers new sociolinguistic and areal-typological methods of the study of language contacts. The author substantiates a systematic approach toward the problem of the ethnic attribution of Ruthenian. Based on the literary, linguistic, and cultural parameters, the author offers to drop the term ‘Old (Middle) Belarusian’ or ‘Old (Middle) Ukrainian’ in reference to this language. [From the publication]