An excerpt from The Power of Myth by Joseph Campbell with Bill Moyers
Moyers: Whats the mythological significance of the belly?
Campbell: The belly is the dark place where digestion takes place and new energy is created. The story of Jonah in the whale is an example of a mythic theme that is practically universal, of the hero going into a fish’s belly and ultimately coming out again, transformed.
Moyers: Why must the hero do that?
Campbell: It’s a descent into the dark. Psychologically, the whale represents the power of life locked in the unconscious. Metaphorically, water is the unconscious, and the creature in the water is the life or energy of the unconscious, which has overwhelmed the conscious personality and must be disempowered, overcome and controlled.
In the first stage of this kind of adventure, the hero leaves the realm of the familiar, over which he has some measure of control, and comes to a threshold, let us say the edge of a lake or sea, where a monster of the abyss comes to meet him. There are then two possibilities. In a story of the Jonah type, the hero is swallowed and taken into the abyss to be later resurrected— a variant of the death-and-resurrection theme. The conscious personality here has come in touch with a charge of unconscious energy which it is unable to handle and must now suffer all the trials and revelations of a terrifying night-sea journey, while learning how to come to terms with this power of the dark and emerge, at last, to a new way of life. 
The other possibility is that the hero, on encountering the power of the dark, may overcome and kill it, as did Siegfried and St. George when they killed the dragon. But as Siegfried learned, he must then taste the dragon blood, in order to take to himself something of that dragon power. When Siegfried has killed the dragon and tasted the blood, he hears the song of nature. He has transcended his humanity and reassociated himself with the powers of nature, which are the powers of our life, and from which our minds remove us.
You see, consciousness thinks it’s running the shop. But it’s a secondary organ of a total human being, and it must not put itself in control. It must submit and serve the humanity of the body. When it does put itself in control, you get a man like Darth Vader in Star Wars, the man who goes over to the consciously intentional side.
Moyers: The dark figure.
Campbell: Yes, that’s the figure that in Goethe’s Faust is represented by Mephistopheles.
Moyers: But I can hear someone saying, “Well, that’s all well and good for the imagination of a George Lucas or for the scholarship of a Joseph Campbell, but that isn’t what happens in my life.”
Campbell: You bet it is — and if he doesn’t recognize it, it may turn him into Darth Vader. If the person insists on a certain program, and doesn’t listen to the demands of his own heart, he’s going to risk a schizophrenic crackup. Such a person has put himself off center. He has aligned himself with a program for life, and it’s not the one the body’s interested in at all. The world is full of people who have stopped listening to themselves or have listened only to their neighbors to learn what they ought to do, how they ought to behave, and what the values are that they should be living for.
