 These kingdoms retained much of their independent identity after the dynastic union of Aragon and Castile, in the face of subsequent efforts towards unification and centralisation by Spanish leaders.Over the past few decades, a concept known as the Catalan Countries ("Països Catalans") has developed as a strand of Catalan nationalism advocated by the Valencian writer Joan Fuster.This is the idea that Catalonia, Valencia, the Balearic Islands and a few other places in Spain and in other European countries are united by the fact that they share Catalan as a historic language, and are in this way distinct from the rest of Spain.