Russian rhetoric began with Mikhail Lomonosov’s Brief Guide to Eloquence (1765), which was written in the classical tradition of the Aristotelian-Ciceronian teaching about effective and persuasive speech. By the time philology had become a unified knowledge system in 1820s, Russian rhetoric stopped being a part of the trivium of verbal sciences, which also included grammar and logic, and evolved into a theory of language arts [slovesnost] that included both fiction and nonfiction literature. Its focus shifted from statement building to development and classification of the existing types and genres of literature. The science gave birth to a new discipline, namely the history and theory of literature, Nikolay Grech being one of its founders. Thus, the subject of rhetoric was mostly the principles of understanding of written fiction. Grech’s concept reflected those new trends in the development of rhetoric while focusing on the analysis of the system of Russian literature as a whole. The present research employed the methods of comparative analysis and analytical interpretation of the text. The article introduces N. Grech’s ideas about rhetorical and fictional prose, as well as his classification of prose and poetry. The author showed how the emergence of borderline, semi-rhetorical, and semi-poetic genres, changed the relationship between prose and poetry and, accordingly, between rhetoric and poetics. From a tool for creating an utterance, rhetoric gradually became a tool for analyzing a finished text.