This paper concerns the topic: “The mathematical work and the social and institutional aspects.” We have attempted to analyze how, in a geometrical construction activity context, the use of intellectual proof can be justified and which way it contributes to stably insert the students’ activity in a natural geometrical axiom. In our thesis project we have shown that situations built on a 3D dynamic geometrical environment can lead the students to rely on this type of geometry. Nonetheless, this evolution would proof itself unstable, and we propose here to examine where the social interactions, and especially via discursive genesis, play a fundamental role in terms of this stability. The proof issue is central to this concern, as it seems to be consubstantial with the transition of assumed Geometry GI to parceled Geometry GII. We propose to analyze the work of three groups of students, inspired on a thesis experiment (Mithalal, 2010), with the purpose of highlighting the interactions between the material activity and the discursive genesis in the geometrical working spaces.