Martin A. S. Hume,
The Court of Philip IV.: Spain in Decadence
“ Let your Majesty hold as the most important affair of your State to make yourself King of Spain. I mean, Sire, that you should not content yourself with being King of Portugal, of Aragon, of Valencia, Count of Barcelona, but that you should strive and consider with mature and secret counsel to reduce these realms of which Spain consists to the laws and form of Castile, without any distinction. If your Majesty succeeds in this, you will be the most powerful Prince in the world. ”
