How should the relationship between immediate interaction and verbal convention be understood? The present article argues that dialogism transcends the distinction between interactionist and constructionist social theories of written communication, as presented by Nystrand and colleagues. The theoretical argument is illustrated by a study of one writer who is struggling to learn argumentative writing. In analyzing this writer's development, the focus is on grounding, specifically, the interplay between foregrounded and backgrounded parts of discourse. The results illustrate that appropriation of conventional resources for grounding is more creative and dyadically contextualized than constructionist theories may invite us to think. Simultaneously, appropriation draws on conventional communicative resources in ways that are hard to explain within interactionist theories. A dialogical model is presented to show that the Bakhtinian "double dialogue" of discourse meets in the "diatope"--that multidimensional (ecological) point of co-constitution where interaction and construction merge into one unified perspective.