Justification Practices in the Mathematics Classroom

The paper contains the partial outcomes of a study focused on analyzing the role played by convincingness in building mathematical knowledge in the classroom setting. The paper describes the findings of an empirical study that is centered on the analysis of a longitudinal case study, in which we analyze the justification practices and convincingness promotion systematically resorted to by a sixth-grade elementary school teacher. In addition to describing the patterns of rationality identified in the classes observed, this paper serves to show that in the classroom setting, reasons-based arguments and motive-based lines of argument can converge within one discursive path. Consequently the justifications are cumulative, apt to be implicit, with blurred outer borders and lack a linear structure.