I was observing one of colleagues teach the other day and learned some interesting things. One of the books banned by the Spanish Inquisition was... the Bible in Spanish. Books of popular piety were also in the index. There was no problem with such material before the rise of Protestantism and Illuminism, but the idea of letting people read the Bible themselves was threatening in a world where Martin Luther existed. The same for Erasmus and humanism generally, which could be unthreatening before Luther but threatening after. You couldn't import books from abroad either, or even from Aragon to Castile, for example. A priest who didn't have great Latin skills could get permission to have a Spanish bible.

This is the closing of the Spanish mind. This is why there has had to been a conscious process of undoing the effects of this ideological closure up to the present day, why José Ángel Valente, for example, has championed the mystic poets of this same period--precisely those who often were in trouble with the Inquisition.

You would think that a certain amount of popular Catholic piety would have been a useful tool against Protestantism, but no. That's not how the Inquisitors felt: If the Protestants read the Bible, then we will show them by stopping people from reading the Bible!