"Nearly everybody in the Middle Ages believed in magic. There were people who took bundles of noxious substances and put them at their neighbors' thresholds to try to harm them. There are a lot of cases where you have a man carrying on an affair, and he might say, 'It's not my fault. The woman bewitched me.'
"Or if you had a lover who decided to marry somebody else, there are magical techniques you could use to make the new spouse impotent or infertile. There were also people who used magical formulas to conjure demons. That was much more frowned upon.
"We actually have medieval manuscripts that give procedures for conjuring demons. It's a kind of spiritual wrestling contest, OK? The assumption is that if you have the proper formulas, you can control them. The magician might say, 'I conjure you by the birth, death, and resurrection of Christ, so that you can carry out my will.'
"The people who are using that kind of magic are chiefly clergy. There were clergy misbehaving in the Middle Ages, just as there are some clergy misbehaving today. In the Middle Ages, exorcism and conjuration meant basically the same thing. If you were a priest authorized to get rid of demons, that's one thing, but if you were conjuring demons to kill people or drive them mad or learn about the future or find out who stole your money, that was not approved.
"There's one magical text which tells you you're supposed to be very careful about who gets ahold of it, and before you die you should pass it on to some trustworthy person. If you can't find a trustworthy person, bury it. I've looked at some of these things in the British Library, and oh my goodness, some of them do look as if they've spent time underground.
"In one manuscript I edited, one of the conjurations is for summoning a flying horse. I got a phone call from a gentleman in India who had tried this conjuration twice, and it didn't work. He wanted to know what I did to make this work. Once I stopped laughing, I had to tell him, 'I'm not a practicing magician. I am a mere historian.'
"There's a bird that functions prominently in medieval magic called the hoopoe. Have you ever seen a picture of a hoopoe? It's cinnamon colored, with black-and-white stripes and an exotic crest. One spell says: Take a hoopoe, behead it at sunrise under a new moon, and extract its heart and gulp its heart down while it's still palpitating, and you'll gain knowledge of all secrets earthly and heavenly. Is that weird enough for you?
"There was a teenage boy who struck up an e-mail correspondence with me. He was trying to do some sort of magic, and he wanted to know if he could substitute a bluebird for a hoopoe. I tried to discourage him. It wasn't doing good things to the hoopoe.