The Proto-Indo-Europeans saw the cosmos as centered around a tree and surrounded by water, which also rose up through a well to feed the tree. The tree was the cosmos itself, an ordered arrangement of things and actions, and the water was chaos, disorder. Notice that order is fed by disorder. Left to itself, order, like an unwatered tree, becomes brittle and dead. An influx of chaos is vital to its life. Chaos is dangerous and not capable of supporting life on its own, however, and only becomes meaningful when it is drawn into Order. It is through this interaction (a kind of ghosti-relationship) that the universe can continue to exist.

http://www.ceisiwrserith.com/pier/whatwasreligion.htm