Symbolism, Imagery, Allegory
Break out your best Lion King impression—we're talking about some serious circles of life.
Er—make that cycles. Because Campbell is less about 2D spheres and more about loop-de-loops.
Everywhere you go in Campbell—from the Hero's Journey itself to the beginning and end of the universe—you find the cycle. Something new (a person, a species, a whole dang reality) comes into being. It grows and thrives, expands, and eventually decays and is swallowed back up by the cosmos, which promptly starts the whole thing all over again.
Yeah, we know. Campbell can sound a lot like your friend who's really into blacklight posters and wants nothing more than to go to Burning Man. But Campbell's also a crazy-smart guy, so keep listening.
This cycle, according to Campbell, is the universe's natural state of being, and as we go through life, our own cycle of birth, growth, death, and rebirth takes place over and over again.
As the consciousness of the individual rests on a sea of night into which it descends in slumber and out of which it mysteriously wakes, so, in the imagery of myth, the universe is precipitated out of, and reposes upon, a timelessness back into which it again dissolves. (242.2)
The easiest example of this symbol to understand is day turning to night and then back to day again…both because a) we live it so often and b) because it shows up everywhere in literature. You can see it in the Book of Genesis, for instance. But you can also see it with heroes growing old and dying (think Han Solo in The Force Awakens—sniff), and with civilizations rising and falling in both fiction and history.
It's all part of the big cycle, and the only time any real evil comes from it is when someone or something tries to stop that big wheel from turning.