This paper examines the role of multimodal rhetoric in processes of theorization. Empirically, we investigated the theorization process of a highly disruptive innovation in the history of architecture: reinforced concrete. Relying on archival data from a prominent French architectural journal in the period from 1885 to 1939, we studied the rhetorical modes at play in the theorization of reinforced concrete. First, we found that theorization entailed two recursive activities: dramatization and evaluation. While dramatization relies on both verbal and visual (i.e. multimodal) means, evaluation relies on verbal means. We integrated these components into a dynamic model of theorization that explains how visual discourse contributes to theorization beyond the effects of verbal discourse.