Discussions about multimodal argumentation have long been hindered by doubts about whether non-verbal artifacts can express propositions. The opponents of multimodal argumentation have stated that semiotic modes other than language lack the precision required to express verifiable statements about the world. The aim of this article is to demonstrate that the account of propositions presented in speech act theory is suitable for analyzing multimodal communication, which is why multimodal argumentation can be studied in the pragma-dialectical tradition. By connecting Searle’s approach with the pragma-dialectic argumentation schemes, I suggest that the propositional act is constructed of three, and not two, elements: referring expression, predicating quality, and proposition scheme, the latter being a characterization of the relationship between the first two. I derive proposition schemes directly from argumentation schemes, noticing that the pragma-dialectical argumentation schemes actually characterize the relationship within propositions, and not between them. Based on that notion, I argue that when interacting with seemingly ambiguous multimodal artifacts, the receiver automatically chooses the most probable connection between the referring expression and the predicating quality from the list of proposition schemes, explaining why multimodal communication can be easily interpreted intuitively. Finally, I analyze several argumentative examples to illustrate how the proposition schemes can be used in reconstructing the reasoning expressed multimodally.