I WAS sitting in a commuter train to London the first time I felt supernatural power rip through me. I was 23, and one year into my graduate training in anthropology. I had decided to do my fieldwork among educated white Britons who practiced what they called magic. I thought of the topic as a clever twist on more traditional anthropological study of strange “native” customs.

I was on my way to meet some of the magicians, and I had ridden my bike to the station with trepidation and excitement. On the train, as the sheep-dotted countryside rolled by, I was reading a book by a man they called an “adept” — someone they regarded as deeply knowledgeable and powerful.

The book’s language was dense and abstract, and my mind kept slipping as I struggled to grasp what he was talking about. The text spoke of the Holy Spirit and Tibetan masters and an ancient system of Judaic mysticism called kabbalah. The author wrote that all these were just names for forces that flowed from a higher spiritual reality into this one, through the vehicle of the trained mind. And as I strained to imagine what the author thought it would be like to be that vehicle, I began to feel power in my veins — to really feel it, not to imagine it. I grew hot. I became completely alert, more awake than I usually am, and I felt so alive. It seemed that power coursed through me like water through a chute. I wanted to sing. And then wisps of smoke came out of my backpack, in which I had tossed my bicycle lights. One of them was melting.

People believe what they believe for a range of reasons, but one of the most puzzling — at least for those who have not had events like these — is an explanation from personal experience. Such moments have cherished roles in conversion narratives, of course.