The article is devoted to the analysis of the origin and development of the Russian literary language in the context of the historical and linguistic tradition of Moscow State University, headed by Professor M. L. Remneva. T. The key stages in the formation of the literary language of Ancient Rus', the interaction of the Church Slavonic written tradition with the living East Slavic language, and the emergence of two types of grammatical norms—strict and relaxed—are also examined. Particular attention is paid to the problem of the language norm and its historical determinacy, as well as the functional difference between bookish and non-bookish language in the context of diglossia. The author analyzes various concepts of the origin of the Russian literary language, including the views of I. I. Sreznevsky, A. A. Shakhmatov, S. P. Obnorsky and V. V. Vinogradov, comparing them with the modern point of view of the historical-linguistic school of Moscow State University. The article demonstrates that the formation of the Russian literary language is a complex process of interaction between the written tradition and the vernacular language, where the bookish language functioned as a means of codification and standardization, and the non-bookish language as a reflection of living vernacular speech. The study is significant for the study of the history of the Russian literary language, linguistic norms and the relationship between written and oral traditions.