One spring night in 1872, a respectable Canadian doctor climbed into a horse-drawn cab after an evening of reading poetry with friends, and somewhere on the quiet ride home he was, without warning, engulfed in light. Not a lamp. Not the moon. An inner fire, he said, that seemed to fill him and the sky at once, and with it came a flood of joy and a single overwhelming conviction: that the universe was not dead matter but a living presence, and that he was, somehow, one with all of it. It lasted only minutes. He spent the rest of his life trying to understand what had happened, and in doing so he gave a name to the widest experience a human being can have.

The doctor was Richard Maurice Bucke, and he was not a mystic by trade. He was a psychiatrist, the superintendent of an asylum in Ontario, a serious man of medicine in the late nineteenth century. He was also a devoted friend and eventual biographer of the American poet Walt Whitman, whose sprawling, ecstatic verse he loved, and it was an evening spent reading Whitman and the English Romantic poets aloud with friends that preceded his experience. Riding home in the carriage, still glowing from the poetry, he was suddenly overtaken. By his own account he thought at first the city was on fire; then he realized the fire was within him. And in that brief blaze he felt he saw, directly, that the cosmos is alive, that consciousness is woven through everything, that death is a kind of illusion, and that the foundation of reality is not indifference but something closer to love. The whole thing passed in a few minutes and never returned in that full form. But he said it taught him more in those minutes than years of study, and that he could never afterward doubt what he had seen.

Now, I want to plant the honest frame in the very first episode, because this is the season where it matters most. I cannot tell you whether Bucke glimpsed the true nature of reality or had a vivid, self-generated brain event of the kind that can produce overwhelming certainty about things that may or may not be so. That question runs under this entire season and I will not pretend to settle it, because no one honestly can. What I can do is take his experience seriously as an experience, and notice the genuinely interesting thing he did next, which lifts him above being just one more person with a story.

Being a scientist by temperament, Bucke didn't just treasure his illumination privately. He went looking to see whether it was a known thing. He began collecting cases, historical and contemporary, of people who seemed to have had the same experience, and he became convinced he was looking at a distinct, recognizable, recurring state of mind, with consistent features, that had appeared again and again across history in different cultures and centuries. In 1901 he published his findings in a book with a title that named the state for the modern world: Cosmic Consciousness. In it he argued that certain figures across history, and he named a sweeping list including founders of religions, poets, and philosophers, had all touched the same elevated form of awareness, and he tried to lay out its common marks: a sudden onset, an experience of light, an overwhelming sense of unity with the cosmos, a feeling of immortality or the unreality of death, joy, and a moral transformation that outlasted the experience itself.

You can push back on almost everything about Bucke's book, and people have. His theory that this was the next evolutionary stage of humanity is dated and grandiose. His list of who qualified is subjective and reflects his own admirations. His method was more the enthusiast's than the rigorous scientist's. All fair. But strip the dated theorizing away and something durable remains, and it's the reason we start the season here: Bucke was among the first to insist, from within medicine, that this overwhelming experience of cosmic unity is a real, specific, recurring feature of human consciousness, not a random madness and not the property of any single religion, but a natural human possibility that shows up, unbidden, in poets and doctors and prophets alike. He treated the widest experience a person can have as a phenomenon worth studying rather than worshipping or dismissing.

And that reframing, from private revelation to studyable human phenomenon, is exactly the move that a greater thinker, working at the same time just across the border, was about to make with far more rigor and far more caution. Because while Bucke was collecting his cases, one of the founders of modern psychology was preparing a set of lectures that would treat these experiences as data, and would give us the four precise features that mark them, still the best short description we have.

Next episode: William James, the varieties of the experience, and the four marks of the mystical.