Owen Barfield, in his most important work, Poetic Diction, explains how all words carry with them a history, an embedded memory of sorts. This memory retains some of it’s power even if the user of the word is not fully aware of it. This is the key (or at least one of the keys) to understanding the effectiveness of poetry.
Tolkien (a close friend of Barfield) thought the same thing and says so here while talking about Sir Gawain and the Green Knight, though he is speaking about the larger genre of fairy-story:
Behind our poem stalk the figures of elder myth, and through the lines are heard the echoes of ancient cults, beliefs and symbols remote from the consciousness of an education moralist (but also a poet) of the late fourteenth century. His story is not ABOUT those old things, but it receives part of its life, its vividness, its tension from them. That is the way with the greater fairy-stories – of which this is one. There is indeed no better medium for moral teaching than the good fairy-story (by which I mean a real deep-rooted tale, told as a tale,and not a thinly disguised moral allegory). As the author of Sir Gawain, it would seem, perceived; or felt instinctively rather than consciously: for being a man of the fourteenth century a serious, didactic, encyclopaedic, not to say pedantic centry, he inherited ‘faerie’, rather than turned deliberately to it.
-J.R.R. Tolkien, Sir Gawain and the Green Knight (Essay from The Monsters and the Critics, p.73)
What struck me is how different the poet’s natural situation was to our own. What have we inherited? The enlightenment, the industrial revolution, the information age, the cults of science, materialism and nihilism. When we turn to faerie, it must be deliberately. Perhaps our children will not need to make so great an effort.