Edward Crowley was a man of many talents. He studied chemistry at Cambridge - a period to which he later attributed his skeptical scientific outlook - but he soon abandoned the idea of a career in science and turned to his other passions. For a while he played competitive chess at the national level. He took to mountain-climbing, and became one of the early 20th century's premier mountaineers, co-leading the first expedition to attempt K2 in the Himalayas. He also enjoyed writing poetry and travelling the world, making it as far as Nepal and Burma in an era when steamship was still the fastest mode of transportation and British colonialism was still a thin veneer over dangerous and poorly-explored areas.
But his real interest was mysticism. He travelled to Sri Lanka, where he studied meditation and yoga under some of the great Hindu yogis. After spending several years there, he achieved a state of mystical attainment the Hindus call dhyana, and set about trying to describe and promote yoga to the West.
He was not the first person to make the attempt, but he was certainly the most interesting. Although his parents were religious fanatics and his father a fundamentalist preacher, he himself had been an atheist since childhood, and he considered the vast majority of yoga to be superstitious claptrap. He set about eliminating all the gods and chants and taboos and mysterian language, ending up with a short system of what he considered empirically validated principles for gaining enlightenment in the most efficient possible way.
Reading Crowley's essay on mysticism and yoga at age seventeen rewrote my view of religion. I had always wondered about eastern religions like Buddhism and Hinduism, which seemed to have some underlying truth to all their talk of "enlightenment" and "meditation" but which seemed too vague and mysterious for my liking. Crowley stripped the mystery away in one fell swoop.
When listening to Eliezer debate Adam Frank on "religious experience", I was disappointed but not surprised to hear just how little they had to say. Even Frank, who was fascinated enough to write a book about it, considered it little more than a sense that something was inspiring or especially impressive. I quoted a bit of Crowley's essay on the thread, and people seemed to like it and want to know more.
But I am very reluctant to share, and do so now only after being specifically requested by a few people. You see, I have been trying to paint a sympathetic view of Crowley over the past few paragraphs. With the unsympathetic view you are familiar already. Under his nickname "Aleister", he wrote some of history's most influential occultist works. Even in this domain, he held himself to a high rationalist standard, recording that he tested each spell and ritual beforehand and passed on only the ones that actually worked as advertised.
...I don't know what that means either. Either he was one of those psychopaths gifted with the ability to lie perfectly and absolutely, or a psychotic genius able to induce hallucinations in himself at will. Crowley himself occasionally endorsed this latter explanation, but after pondering it a while decided he didn't care. The important thing, he wrote, was to determine what techniques produced what results. After that, the philosophers could determine whether they were physical or mentally mediated. Besides, he said, the entities he summoned were so different from himself that if they represented faculties of his mind, they were ones to which he had no conscious access.
My point is that I am going to link you to Crowley's essay on mysticism, yoga, and religious experience, and that you might get more out of it if you tried to avoid any bias upon seeing the name "Aleister Crowley" on the title page. Yes, I feel properly guilty posting this on a rationalism site, but if we're going to talk about religious experience we might as well listen to the people who have had some.
Although it is Less Wrong tradition to rewrite a theory rather than simply link to it, it would be inappropriate in this case. Getting Crowley filtered would be like having someone summarize Godel, Escher Bach to you - you might learn a few things, but you'd lose the chance to enjoy the superb writing. It's a long essay, but not so long you can't read it in one sitting. Even just reading the Preface gives an idea of the theory. Without further ado: Crowley on Religious Experience.
I post this essay to clarify why I believe three things. First, that both Eliezer and Adam miss the point of religious experience. Second, that certain seemingly supernatural or silly beliefs can be more reasonable than they appear (see for example Crowley's explanation of religious laws on "virtue" and "purity"). Third, that some mystics' work is of sufficient relevance to rationalists to be worth study.