Vygotsky stated that concepts cannot be transmitted from mind to mind but instead developed through communication. Specifically, the instructional use of language would be the means for concept development. However, there is evidence to show that school concepts are particularly difficult to develop. Argumentation has been shown to promote the development of school concepts, but why is this the case? Although there are different theoretical accounts for this effect, none of them are developed from an explicit notion of what it is to understand and develop a concept. The purpose of this paper is to revisit these accounts in light of dialogical theories of meaning comprehension in order to shed light on this old problem. After discussing conceptual change and Vygotsky's theory of concept development, a dialogical notion of meaning comprehension informed by Bakhtin is discussed. Finally, the conclusion is drawn that imagination plays a central role in concept development and that argumentation is a powerful means for imagining.