Jung developed his idea of archetypes mostly as a way of finding meaning within the dreams and visions of the mentally ill: if a person believes they are being followed by a giant apple pie, it's difficult to make sense of how to help them. But if the giant apple pie can be understood to represent that person's shadow, the embodiment of all their fears, then the psychotherapist can help guide them through that fear, just as Yoda guided Luke on Dagoba. If you think of a person as a computer and our bodies as "hardware," language and culture seem to be the "software." Deeper still, and apparently common to all homo sapians, is a sort of built-in "operating system" which interprets the world by sorting people, places, things and experiences into archetypes.
Campbell's contribution was to take this idea of archetypes and use it to map out the common underlying structure behind religion and myth. He proposed this idea in The Hero With a Thousand Faces, which provides