|This article relies on references to primary sources. (March 2009)|
It was incorporated in 1970, and its founders came from different academic, social, professional and political affiliations. What joined them was a great desire for change and to establish a diverse social activism: academic associations, a practice of political opposition against the system of the Estado Novo regime that ruled Portugal since the 1920s, participation in Christian organizations and trade union activities. A common denominator animated the founders of SEDES: humanism, socio-cultural development and democracy.
SEDES held meetings, organized themselves into working groups, facilitated debates on various locations of Portugal, was the first Portuguese organization to proclaim the advantages of a rapprochement with the European Community and was a pluralistic school of civics.
With the advent of democracy on 25 April 1974, many of his associates have contributed to the social and political life of the country in various political parties. Perhaps there has not been a single government since the April 25, which do not contain among its members figures associated with SEDES.