The paper compares the rhetorical, grammatical and discourse approaches to the study of language by focusing on issues of systematization and the contrast between controlled and adaptive systems. The key category of the analysis is homeostasis, a system to maintain its functions within certain limits. First, the study interprets the social meaning of rhetorical systemizations, traditionally interpreted as pre-scientific and terminologically laden, and identifies the reasons why the ancient systematization was successful but cannot be applied to o grammar. Then the idea of rhetoric as a secondary grammar is challenged by contrasting grammar as a controlled system and rhetoric as an adaptive system; while grammar selects discrete variants, rhetoric constructs continual metaplasms. Similarities between rhetoric and grammar concerning unmarked forms are also considered irrelevant because neutral forms cannot be produced for each trope and figure, which is proven by rhetorical period. Finally, the paper states the proximity of the discourse and rhetorical approaches. Different interpretations of discourse demonstrate different relations with rhetoric. The discursive approach is productive beyond the speech act, which means that the discursive community can be considered in terms of homeostasis. This idea is illustrated by the problems faced by individuals in joining the academic discourse community, communicating within it, and the viability of the community itself. The difference between the rhetorical and grammatical approaches determines the strategies of language teaching and language study. The paper concludes that the rhetorical approach can contribute to the concept and framework of discourse if this framework is constructed with reference to homeostasis.