Inspired by Bakhtin's and Vygotsky's theories of learning, this project explores how "allowing not-knowing" is enacted within collaborative student-led seminar discussions. Earlier research on student reflections (Feito, 2002) suggested that in successful seminars, participants regularly acknowledge their lack of understanding, offer partial understandings, and collectively develop new meanings. This project tracks these phenomena within actual classroom discourse. A detailed discourse analysis of a small "Great Books" seminar session (N = 16) describes how students construct a learning environment conducive to not-knowing and the open-ended construction of meaning. The students used discourse markers and sequencing to invite the recursive manipulation of ideas by the group. Breakdowns in the sense of shared validity engendered dead-end disagreements wherein students regressed to less collaborative forms of discourse and appealed to personal authority. Non-linear topic patterns and the deferral of closure cognitively challenged them to hold and reconstitute ideas over lengthy periods of time.