Profit-with-purpose corporations (PPCs) are new corporate forms that include a commitment of social or environmental nature in their by-laws. Because of its binding nature, we expect that a purpose introduces some stability and may freeze an identity or some institutional logics within PPCs. But what happens when the purpose is formulated as a challenge or as an innovative goal? To what extent does it create a new identity, or new institutional dynamics? Methodologically, as the new legal framework is too recent in Europe to allow empirical analysis, the study is based on an empirical case of PPC: La Poste, an incumbent company of public service in France. We have studied the way the mission has been historically defined in this company, and regularly revised contractually. We have also identified conception patterns used by the department in charge of exploring new societal commitments of the company. Our work reveals important phenomena with strong implications: the case shows that a purpose-driven corporation may need to continuously reformulate its purpose and to revise its identity accordingly. It also indicates that a generative purpose leads to a systematic effort to designate new concepts that precisely call for the construction of new institutional logics. Far from institutionalizing specific logics or an identity, the purpose appears as a lever for renewing the organizational identity as well as the institutional logics present within the company.