This exploratory, descriptive study examined the way five chemistry teachers from four different schools enacted their visions of an activity labeled as the multiple solution pathway (MSP) lesson structure – one in which students were given a relevant problem to solve and the opportunity to propose and explore several solutions to the problem. A theoretical and analytical framework for characterizing what transpired within these enactments was developed mainly out of Bereiter's principle of progressive discourse and its accompanying commitments, but also by drawing on Peirce‘s fallibilist epistemology, Gal'perin's notion of the orienting basis of an action, and Davydov's distinction between empirical and theoretical generalizations. Data from utterance-level discourse analysis of the videotaped lessons, supplemented by pre- and post-lesson interviews with both students and teachers was used to answer the research question: What is the nature of the interactions that occur during Multiple Solution Pathway (MSP) lessons and how are those interactions related to the structure of activity and the way in which ideas are explored within those lessons? The data showed that there were two general structures of activity utilized by the five teachers and that these different structures impacted the extent to which two of the progressive discourse commitments (expansion and openness) were supported. It also indicated that the teachers likely operated off a 'teacher as evaluator' metaphor and a discrepant event vision of the way the lesson should unfold, both features of which limited the extent to which progressive discourse was maintained in these lessons. Pedagogical implications for more fully realizing the potential of the MSP structure are presented.