The work deals with the preliminary meaning and value of solidarity as it evolves over time, to understand how it is embodied in the individual consciousness and collective responsibilities. Solidarity has no way of being without the subsidiarity: the ideological line that directs the modern policies of welfare. These policies are attentive to a new concept of poverty not related to survival needs, but to new social indicators. To protect social rights of the person means to realize that we need to invest in knowledge, today main instrument of emancipation of the individual. The last part of the work is devoted to the analysis of how the EU has looked at social issues, in line with the principle of solidarity and directing its legislation to that effect. The author makes conclusively reservations and raises objections to the delay with which the Union has intervened in social policies.