conventional wisdom of 1380

the cloud of unknowing was written around 1380, and this piece of conventional wisdom found it's way into the book. at first i was surprised. but then it made me wonder about the things we take for granted today and repeat as if they were fact. <--- For as I have understood by some disciples of necromancy, the which profess the advocation of wicked spirits, and by some unto whom the fiend hath appeared in bodily likeness: in what bodily likeness the fiend appeareth, evermore he hath but one nostril, and that is great and wide, and he will gladly cast it up so that a man may see in thereat to his brain up in his head. The which brain is nought else but the fire of hell, for the fiend may have none other brain. And if he might make a man look in thereto, he wants no better. For at that looking he should lose his wits for ever. ---> i wonder if the author of the cloud really believed this.....