In this paper we explore the value of theoretical triangulation as a methodological approach for the analysis of classroom interaction. We analyze an excerpt of a whole-class discussion in history from three theoretical perspectives: interactivity of the discourse, conceptual level raising and historical reasoning. We conclude that using theoretical triangulation enables us to relate the perspectives of the teacher, the students and the domain to each other, which provides us with deeper insight into the complex phenomenon of classroom interaction. The analyses reveal the complexities the teacher faces when trying to elicit and promote collaborative knowledge construction and the dilemma of promoting student participation, on the one hand, and deepening the quality of reasoning, on the other. (Contains 7 figures and 1 note.)