C. S. Lewis on Christ as Myth

You ask me my religious views: you know, I think, that I believe in no religion. There is no proof for any of them, and from a philosophical standpoint Christianity is not even the best. All religions, that is, all mythologies to give them their proper name, are merely man's own invention--Christ as much as Loki. Primitive man found himself surrounded by all sorts of terrible things he didn't understand--thunder, pestilence, snakes, etc: what more natural  than to suppose that these were animated by evil spirits trying to torture him. These he kept off by cringing to them, singing songs and making sacrifices, etc. Gradually from being mere nature-spirits these supposed being(s) were elevated into more elaborate ideas, such as old gods; and when man became more refined he pretended  that these spirits were good as well as powerful.
   Thus religion, that is to say mythology, grew up. Often, too, great men were regarded as gods after their death--such as Heracles or Odin: thus after the death of a Hebrew philosopher Yeshua (whose name we have corrupted into Jesus) he became regarded as a god, a cult sprang up, which was afterwards connected with the ancient Hebrew Jahweh-worship, and so Christianity came into being--one mythology among many, but the one we happened to have been brought up in...
--C. S. Lewis, on October 12, 1916 age 17.

Now the story of Christ is simply a true myth: a myth working on us in the same way as the others, but with this tremendous difference that it really happened: and one must be content to accept it in the same way, remembering that it is God's myth where the others are men's myths: i.e. the Pagan stories are God expressing himself through the minds of poets, using such images as He found there, while Christianity is God expressing Himself through what we call "real things". Therefore it is true, not in the sense of being a "description" of God (that no finite man could take in) but in the sense of being the way in which God chooses to (or can) appear to our faculties. The "doctrines" we get out of the true myth are of course less true: they are translations into our concepts and ideas of that wh[ich] God has already expressed in a language more adequate, namely the actual incarnation, crucifixion and resurrection. Does this amount to a belief in Christianity? At any rate I am now certain (a) That this Christian story is to be approached, in a sense, as I approach the other myths. (b) That it is the most important and full of meaning. I am also nearly almost certain that it happened...
--C. S. Lewis, on October 18, 1931, age 32, around the time of his conversion to Christianity.

Both quotes are from Letters of C. S. Lewis edited by Walter Hooper and W. H. Lewis