One of the main research gestures within the Anthropological Theory of the Didactic (ATD) consists in questioning the mathematical knowledge that is at the core of teaching and learning processes. In the case of university education, and because the knowledge at stake is closely related to scholar knowledge, this questioning might seem less necessary and the tendency is to focus on the possible different ways of organizing its teaching. Through the example of Group Theory we illustrate the methodology of questioning proposed by ATD in two different moments of the evolution of this framework: a first one centred on the structure and dynamics of the different components of mathematical praxeologies; a second one more focused on the raison d'être and functionality of what is taught and learnt.