The following reflections deal with a permanent and fundamental challenge that has confronted, and continues to confront, all popular movements struggling against capitalism. By this I mean both those of movements whose explicit radical aim is to abolish the system based on private proprietorship over the modern means of production (capital) in order to replace it with a system based on workers’ social proprietorship, and those of movements which, without going so far, involve mobilization aimed at real and significant transformation of the relations between labor (“employed by capital”) and capital (“which employs the workers”). Both sorts of movements can contribute, in varying degree, to calling capitalism into question; but they also might merely create the illusion of movement in that direction, although in fact only forcing capital to make the transformations it would need to co-opt a given set of working-class demands. We are well aware that it is not always easy to draw the boundary between efficacy and impotence in regard to the strategies resorted to by these movements, no more so than to determine whether their strategic aims are clashing with their tactical situation.