The contribution of the Third Sector is strategic to the start of a transition toward a welfare society, whose realisation depends on the rising of forms of reciprocal and trustful partnership among public, private, Third Sector and informal subjects. The Third Sector plays a specific role in the process of promoting a pluralistic welfare, thanks to new forms of social partnership among Third sector actors, state and market, based on horizontal subsidizing. In this perspective, pluralistic welfare emerges not as sum of different subjects, each dedicated to specific activities and sectors, but as a way of undertaking common actions and fostering relations. The entrance of new players in the welfare systems generates innovative synergies in the answer of the more and more complex social needs; furthermore, the creation of networks among Third Sector players and other players of the pluralistic welfare in the production of social services can spread a culture of solidarity and social responsibility.