Assuming that constitutionalism owes its central place to rights, it is necessary to have criteria by which to analyze the reasons for the inclusion of duties in constitutions. Some of these duties bear a justificatory connection to solidarity. In this connection, challenges arise that essentially stem from this concept’s proximity to equality and from the basic need for a sense of recognition of the other. The constitutionalization of solidarity "resting on a specific philosophic-political model closer to republicanism than to liberalism" makes it possible to identify the welfare state as an optimal model.
Keywords: Duties, solidarity, rights, constitution, liberalism, republicanism.