The two spent about three months touring America, which represented the most intimate point in their friendship. However the close contact and exhausting conversations exposed certain ideological differences that would ultimately tear the friendship apart. Jung's primary disagreement with Freud stemmed from their differing concepts of the unconscious. Jung saw Freud's theory of the unconscious as incomplete and unnecessarily negative. According to Jung, Freud conceived the unconscious solely as a repository of repressed emotions and desires. Jung agreed with Freud's model of the unconscious, as Jung called the personal unconscious, but he also proposed the existence of a second, far deeper form of the unconscious, which underlies the personal one. This was the collective unconscious, where the archetypes themselves resided.

Influenced by America's burgeoning bohemian culture, Freud & Jung spent a short portion of their trip travelling the rails. Photo ca. 1908.