A man did not stand up and say ‘I believe in Jupiter and Juno and Neptune,’ etc., as he stands up and says ‘I believe in God the Father Almighty’ and the rest of the Apostles’ Creed. Many believed in some and not the others, or more in some and less in others, or only in a very vague poetical sense in any. There was no moment when they were all collected into an orthodox order which men would fight and be tortured to keep intact. Still less did anybody ever say in that fashion: ‘I believe in Odin and Thor and Freya,’ for outside Olympus even the Olympian order grows cloudy and chaotic. It seems clear to me that Thor was not a god at all but a hero. Nothing resembling a religion would picture anything resembling a god as groping like a pigmy in a great cavern, that turned out to be the glove of a giant. That is the glorious ignorance called adventure. Thor may have been a great adventurer; but to call him a god is like trying to compare Jehovah with Jack and the Beanstalk. … Polytheism fades away at its fringes into fairy-tales or barbaric memories; it is not a thing like monotheism as held by serious monotheists. … Finally it did satisfy, or rather it partially satisfied, a thing very deep in humanity indeed; the idea of surrendering something as the portion of the unknown powers; of pouring out wine upon the ground, of throwing a ring into the sea; in a word, of sacrifice.
The Everlasting Man, by G. K. Chesterton. From “V. Man and Mythologies”, which is rapidly becoming my favourite chapter in the entire book. I had to resist the urge to quote more.
EDIT: On the next page:
Certainly the pagan does not disbelieve like an atheist, any more than he believes like a Christian. He feels the presence of powers about which he guesses and invents. St. Paul said that the Greeks had one altar to an unknown god. But in truth all their gods were unknown gods. And the real break in history did come when St. Paul declared to them whom they had ignorantly worshipped.