Dualism is a specific quality of approximation principle. The present research featured the potential of approximation principle for linguadidactics, namely to what degree it can be used to teach Russian as a foreign language and perform correction work in class. The research objective was to assess the efficiency of this principle. The study was based on the method of observation. The article introduces analyses of scientific linguadidactic literature and some typical situations of educational process. The author separates correction work from speech activity, i.e. talking, writing, and reading. The author believes that speech mistakes must be corrected immediately, involving the student in the correction process. Graphic facilities should be used to illustrate the norm. Therefore, in practical linguadidactics, approximation principle should be minimal. Yet, approximation is impossible to avoid in the abovementioned types of speech activity, which hints at the dualism of this principle. Therefore, all errors must be corrected using graphic means, if possible, by both the teacher and the student. Students should be encouraged to participate in the correction process, while the teacher maintains supervisory control.