C.S. Lewis is one of my all time favorite authors. He was also a Christian apologist, Oxford don, professor at Cambridge, lover of Greek mythology, and expert in Medieval and Renaissance literature, among other things.
One of the least known things about Lewis is that he was also a poet. The prayer below is both poetry and prayer. I love this prayer because I had never thought of the issues he explains below. Essentially what he is saying is that all of us have in our minds some image of God when we pray to him. But God is beyond any image that we can conceive. So in one sense when we pray and conceive of insufficient images of God, we are committing idolatry. But he goes on to explain that since we are incapable of properly conceiving of God, he condescends to us. He diverts our poorly aimed "arrows," and helps them hit the mark. This is similar to what Paul meant in Romans 8:26 when he said "in the same way, the Spirit helps us in our weakness. We do not know what we ought to pray for, but the Spirit himself intercedes for us with groans that words cannot express."
One more important note. C.S. Lewis would often refer to people, works, or events from history assuming that people would have at least a basic knowledge of them. Unfortunately, that is no longer the case, and one reference in the prayer probably needs explanation. "Pheidian fancies" refers to Pheidias, a first century Greek sculptor who is known for his statue of Zeus at Olympia, one of The Seven Wonders of the Ancient World. He also made many other sculptures of gods and goddesses. So when Lewis refers to our thoughts of God as "Pheidian fancies," he is describing how insufficient are our ideas of God.
He whom I bow to only knows to whom I bow
When I attempt the ineffable Name, murmuring Thou,
And dream of Pheidian fancies and embrace in heart
Symbols (I know) which cannot be the thing thou art.
Thus always, taken at their word, all prayers blaspheme
Worshiping with frail images a folk-lore dream,
And all men in their praying, self-deceived, address
The coinage of their own unquiet thoughts, unless
Thou in magnetic mercy to thyself divert
Our arrows aimed unskillfully, beyond desert;
And all men are idolaters, crying unheard
To a deaf idol, if thou take them at their word.
Take not, O Lord, our literal sense. Lord, in thy great,
Unbroken speech our limping metaphor translate.