From the 12th century on, there were a lot of heretical movements. Now one could argue that the people who didn’t join these movements were ignorant, or were in fear of what happened to the people who did join. . . .
But certainly these heretical movements were powerful voices of critique and they had an effect on the Church.
It is certainly true that free religious choice wasn’t present in the Middle Ages. One can’t assume from the fact that nearly everyone theoretically belonged to the Church that they all were devout and orthodox. in fact we know that they weren’t.
At the same time, we have plenty of evidence of devout, passionate faith in medieval Catholicism, including members of the lower classes. It was a mixed bag. But contrary to the stereotype some have, intelligent lay participation increased throughout the Middle Ages. The period right before the Reformation was a period of intense lay piety.
Protestant and secular historians often try to shoehorn medieval renewal movements into the category of “precursors of the Reformation.” This is prejudiced. One generally good textbook that I used when teaching a class put the Dominicans and Franciscans in the “later Middle Ages” under the category of responses to corruption, while dealing with other 13th-century developments in the previous chapter. That’s a relatively subtle example of the kind of thing I’m talking about.
Not sure how helpful any of this is . . . .
Also, by the later Middle Ages there was quite a bit of literacy, and a lot of religious literature was available in the vernacular. To some extent this was the case from very early on as well–in Anglo-Saxon England, for instance, large chunks of the Bible were translated into English.
Edwin