the Spanish Constitution...explicitly states the `indissoluble unity of the Spanish Nation'

But the definition of a nation usually includes commonality of language and culture. Catalonia is no less distinct on those terms than is Portugal or the Basque areas and Catalonia only became a part of Spain as a historical contingency, with the union of the crowns of Castile and Aragon, and Catalonia was about as different from Aragon as it was from Castile.  

"It is not necessary to have hope in order to persevere."