It seems to me that Mormon discourse has two mutually contradictory ways of talking about revelation during the Middle Ages, and that neither view takes much notice of actual medieval views on the matter.
1. The first narrative, the one to which I am less sympathetic, holds that the heavens were closed and revelation had ceased. On the one hand, this view makes it easy to dismiss as falsehoods all the medieval accounts of visions, revelations, or appearances of Christ or angels or other members of the heavenly panoply. On the other hand, since we do not make a radical distinction between personal inspiration and divine revelation, this view would require us to believe that God spent the better part of 2000 years not answering prayers, which seems a bit petty for a loving God.
2. The second, contradictory narrative holds that of course revelation did not cease, but rather that everyone believed that revelation had ceased, and they were too stubborn to believe otherwise. According to this view, the First Vision contradicted the prevailing notions, and therefore Joseph Smith was subjected to special persecution. One drawback of this view is that it then has to explain what the saints, mystics, and prophets thought they were doing for the previous 1700 years (or what more recent visionaries thought they were doing at the time), if not receiving revelation.
It would be easy to find both notions wrong and somewhat embarrassing, the result of excessive belief in Mormon uniqueness or a misguided assumption of medieval benightedness, were it not for the fact that there is a precedent for the same discussion during the Middle Ages.
St. Birgitta of Sweden (1303-1373) was a pious and, after the death of her husband, a religious woman who went on pilgrimage to Jerusalem, founded a monastic order, and had visions from the time she was a child. The first chapter of the extracts from her revelations known as the Onus mundi addresses the question of why Birgitta was receiving revelation in the first place:
Christ also showed to the archbishop of Uppsala the reason why God had spoken anew in these revelations. For the aforementioned archbishop wondered and said, “God has spoken enough through the prophets of the Old Testament and then after that through himself in the Gospels, and therefore there is no need for him to speak againâ€¦.” Now when Christ wanted to show the reason for it to the archbishop, he spoke to Birgitta in a special revelation: “Say to the bishops when they meet for my sake and especially to the archbishop, ‘You wonder why I speak my words. Open your eyes and see, listen with your ears and note, open your mouth and ask, how I, Christ, have been driven out and scorned by all people, and see how no one desires to have me in their hearts.â€¦You should not wonder that I speak, for if the wisest man in the world could recognize how many souls go to Hell each day, he would understand that there were more of them than sands of the sea or stones in running water. Therefore I have spoken again to see if anyone would repent and abandon sin, so that the number of the damned might be lessened and my flock increased.'” (Excerpted and translated from Ulrich Montag, Das Werk der heiligen Birgitta von Schweden in oberdeutschen Ãœberlieferung, 1968, pp. 257-261.)
Now, the relationship between transcribed, translated, and redacted words on a page and Birgitta’s original intent is a particularly thorny problem, but the passage does at least indicate that one real problem faced by fourteenth-century prophetic voices, or by those who chose to associate with them, was the belief that no further revelation was necessary after the Old and New Testaments. This belief was not by any means universal, but it was present and could be used by existing religious authority to suppress a would-be prophet. (Birgittaâ€™s answer is a matter of spiritual utility: if someone listens to her revelations, his or her chance of going to Hell decreases.)
Some few days after I had this vision, I happened to be in company with one of the Methodist preachers, who was very active in the before mentioned religious excitement; and, conversing with him on the subject of religion, I took occasion to give him an account of the vision which I had had. I was greatly surprised at his behavior; he treated my communication not only lightly, but with great contempt, saying it was all of the devil, that there were no such things as visions or revelations in these days; that all such things had ceased with the apostles, and that there would never be any more of them.
I don’t think it makes sense for us to adopt the attitude of the preacher, that there was no revelation, nor do we need to dismiss Joseph Smith’s autobiographical account as a bit of self-important posturing; there really were and are important people who see continuing revelation as superfluous or even diabolical. Instead, Joseph Smith and the Methodist minister, like Birgitta and the archbishop of Uppsala, were each taking part in a long and ongoing and often contentious conversation about prophetic and ecclesiastical authority.