Abstract: This article examines the category of modality and its role within the structure of a persuasive text based on the research materials of the experts in the theory of argumentation (S. Toulmin, C. Perelman, L. Olbrechts-Tyteca) and scholars of rhetoric (Y. V. Rozhdestvensky, A. A. Volkov). The theory of argumentation observes two concepts of modality: according to one, modality is an integral part of the argument, according to the other – a way to express thoughts emphasizing the point of statement. The author draws parallel between the views of other researchers and the own definition of modality, which indicates the status of a sentence in relation to reality/unreality (semantic modality) or express an illocutionary function of the statement (pragmatic modality). The article provides a representation of modality not only within the framework of the theory of argumentation, but also rhetoric as a whole. The points of intersection are traced between the views of the experts in theory of argumentation and the scholars of rhetoric. The hypothesis is advances that in oratorical prose, modality alongside other modus categories, contributes to the expression of two rhetorical goals: to convince the addressee of their views (evaluation) and to convince the addressee to act by necessity (prescription). It is concluded that rhetoric broadens the understanding of modality in science and provides instruments for analyzing the role and place of modality in a persuasive text.