A founding member of the Society for Catalan Historical Studies (Societat Catalana d’Estudis Històrics), a branch of the Institute for Catalan Studies (Institut d'Estudis Catalans), he directed the Great Catalan Encyclopaedia from 1965 to 1971.
He participated in several initiatives to oppose the Francoist State, such as the Assembly of Catalonia (Assemblea de Catalunya), and was a founder of the left-wing Catalan nationalist movement, Nacionalistes d’Esquerra. From 1996 to July 2004, he was the President of Esquerra Republicana de Catalunya, and later held the post of Honorary President, following his having been succeeded in the active political position by Josep-Lluís Carod-Rovira.