When trying to help teachers cope with the critical situations they face in classrooms, public policies are mainly concerned with improving initial teacher training. I claim in this article that the role of lifelong learning should no longer be undermined and that the design of teachers' training should be supported by a thorough examination of the cognitive processes involved. A faulty view of cognition may explain both our emphasis on initial training and most of the difficulties faced in designing teachers' training. Searching existing alternative metaphors of cognition and investigating new ones constitutes a way of coping with these problems: first to design new forms of training, second to understand the processes involved in innovative training methods that have already been implemented. My focus in this article is precisely the "metaphor of cognition" that underlies innovative teacher training methods. This metaphor is based on Peirce's pragmaticism, and it describes teachers' training as a process of taking and changing habits. This article mainly investigates the links between Peirce's later semiotics, Merleau-Ponty's "Phenomenology of Perception" and Varela's theory of enaction, in order to propose a threefold definition of "habit" and define the notion of "educational gesture", which constitutes a translation of the concept of habit in the field of education and training.