According to the main ideas that one may extract from Marx's work on a transition theory, the socialism would be an intermediate stage for a superior system - the communism - made possible only after the complete development of the productive forces, capitalism's 'historical mission'. Nevertheless, this thesis represents one of Marx's biggest controversies, although his intense and huge analysis on the capitalism, which made possible important advances on the social practice and science. History has demonstrated that the reproduction and the expansion of the capitalism have not been limited by the advance of the technique and that, neither, a transition process would emerge from a sudden revolutionary reaction. In this work, we put on discussion some aspects of Marx's thought, his transition theory and the current process of crisis of the reproduction of the capitalist relations of production. The conclusions bring us to the thesis that the possibilities of reaching something that deserves to be called socialism depends directly on the development of relations of solidarity (very beyond the advance of the productive forces) and on the individual's political perception in front of the society - that starts to be demonstrated by a series of experiences of self-management with the heading of solidarity economics.