BACKGROUND: While farming in France and generally in Europe is continuing to intensify, at the expense of its environmental sustainability, promising alternatives are emerging. OBJECTIVE: The processes whereby farmers change and transform their own work, to shift from an intensive mode of production to a self-sufficient and autonomous one, need to be formalized if we are to further our understanding of why and how these forms of sustainable farming activity emerge. METHODS: We use the development of professional worlds theory, a systemic representation of workers' activity, whereby their experience is formalized. This can be explained as the praxis (1), conceptual and axiological underpinnings form a system with the object of the action. The development of a professional world is analyzed according to the evolution of its components and the search for pragmatic coherence within it. We analyzed professional transitions towards self-sufficient and autonomous mixed farming through a case study. RESULTS: Our findings showed that the transition is initiated by the discovery of the unthinkable, awareness of a discrepancy between what the farmers think and what they do, the appearance of problems, and the response to external constraints. Professional transition is a non-teleological and non-incremental process; it corresponds to a comparison with reality, and a resolution of difficulties. This process is stimulated by the use of artifacts instrumented by the farmers. CONCLUSION: New perspectives are opened up by this formalization of transitions, in terms of (i) support towards sustainable farming and (ii) the design of sustainable farming systems. (1) Praxis refers to the overall coordination functions and adapt core voluntary movements in order to accomplish a given task.