Jung found one of his dreams particularly troubling. In the dream, Jung and a traveling companion confronted two gates. As he considered which to pass through, both gates shut, and his companion cried out that they would remain stuck in the 17th century. Jung wrestled with what the dream might mean and began searching the historical period for clues. His research led him to alchemy—something that he had always dismissed in the past as nonsensical. The psychiatrist spent years reading alchemist texts and began to see correlations with his own work. Alchemists utilized a series of symbols—an approach that had become central to Jung’s theories.

After spending years studying his own unconscious and sifting through the symbols he found there, Jung was able to look at his fantasies and experiences with an objective eye. He briefly shows how each development in his work led to the next. Jung believed that recurring archetypes, which appeared in the human psyche, were present throughout history and literature. These archetypes were a part of the experience of the collective unconscious.