A big man with wire-rimmed glasses, a booming laugh and a penchant for the experimental, Jung was interested in the psychological aspects of séances, of astrology, of witchcraft. He could be jocular and also impatient. He was a dynamic speaker, an empathic listener. He had a famously magnetic appeal with women. Working at Zurich’s Burghölzli psychiatric hospital, Jung listened intently to the ravings of schizophrenics, believing they held clues to both personal and universal truths. At home, in his spare time, he pored over Dante, Goethe, Swedenborg and Nietzsche. He began to study mythology and world cultures, applying what he learned to the live feed from the unconscious — claiming that dreams offered a rich and symbolic narrative coming from the depths of the psyche. Somewhere along the way, he started to view the human soul — not just the mind and the body — as requiring specific care and development, an idea that pushed him into a province long occupied by poets and priests but not so much by medical doctors and empirical scientists.

Jung soon found himself in opposition not just to Freud but also to most of his field, the psychiatrists who constituted the dominant culture at the time, speaking the clinical language of symptom and diagnosis behind the deadbolts of asylum wards. Separation was not easy. As his convictions began to crystallize, Jung, who was at that point an outwardly successful and ambitious man with a young family, a thriving private practice and a big, elegant house on the shores of Lake Zurich, felt his own psyche starting to teeter and slide, until finally he was dumped into what would become a life-altering crisis.

What happened next to Carl Jung has become, among Jungians and other scholars, the topic of enduring legend and controversy. It has been characterized variously as a creative illness, a descent into the underworld, a bout with insanity, a narcissistic self-deification, a transcendence, a midlife breakdown and an inner disturbance mirroring the upheaval of World War I. Whatever the case, in 1913, Jung, who was then 38, got lost in the soup of his own psyche. He was haunted by troubling visions and heard inner voices. Grappling with the horror of some of what he saw, he worried in moments that he was, in his own words, “menaced by a psychosis” or “doing a schizophrenia.”

He later would compare this period of his life — this “confrontation with the unconscious,” as he called it — to a mescaline experiment. He described his visions as coming in an “incessant stream.” He likened them to rocks falling on his head, to thunderstorms, to molten lava. “I often had to cling to the table,” he recalled, “so as not to fall apart.”