This paper investigates the teacher's role in discussion-intensive pedagogy, arguing that one of the teacher's roles is to support an atmosphere of intellectual ferment. It offers possible language and stance for examining, describing, and analyzing these aspects of classroom discourse; language that is capable of finer distinctions, and a stance that is less aimed at evaluation. Teachers must manage productively the inevitable disagreements among students and between students and accepted mathematics. They must focus discussions, clarify students' views, and engage students in the examination of others' ideas. Making substantive mathematical comments or "telling" is one way that teachers can move students away from entrenched disagreements or provide useful disequilibrium and disagreement in the classroom. Two actual classroom episodes are presented to ground the discussion in a close view of the challenges posed for the teacher's role, followed by an analysis of the situations and the pedagogical issues posed. (Contains 29 references.) (NAV)