This paper aims to show that, contrary to the standard understanding of his work, Sen's idea of justice does not consist in the defense of a capability theory. Under the dominant capability-centered view, Sen's idea of justice is indeed characterized principally by a switch of focus from utility to capability. We demonstrate that this view amounts to the application of formal welfarism to capabilities. We reject this characterization and defend instead a heuristic account of the status of capability in Sen's thought: capability was introduced to make a point against welfarism, but this does not imply that a commitment to a capability theory. The capability-centered view is shown to be inconsistent with Sen's idea of justice, because the latter requires agents to be involved in the definition of their own welfare. Our study of the status of capability in Sen's view of justice enables us to relocate his main contribution and to build the basis for an alternative theory of justice.