Below is an excerpt from Mircea Eliade's book, "Myths, Dreams and Mysteries: The Encounter Between Contemporary Faiths and Archaic Realities." Harper & Row, Publishers: New York. 1960. Pg. 225.
What we have here is an initiatory adventure undertaken to gain an item of secret knowledge. One goes down into the belly of a giant or a monster in order to learn science or wisdom. That is why the Lapp shaman remains in the fish's entrails for three years---to learn the secrets of Nature, to resolve the enigma of life and see into the future. But, if entering into the belly of a monster is equivalent to a descent into Hell, into darkness among the dead---that is, if it symbolises a regression to cosmic Night as well as into the darkness of "madness" where all personality is dissolved---and if we take account of all these homologies and correspondences between Death, Cosmic Night, Chaos, madness as regression to the embryonic condition, etc., then we can see why Death also symbolises Wisdom, why the dead are omniscient and know the future, and why the visionaries and the poets seek inspiration among the tombs. Upon another plane of reference, we can also understand why the future shaman, before becoming a wise man, must first know "madness" and go down into darkness; and why creativity is always found in relation to some "madness" or "orgy" involved with the symbolism of death and darkness.