Lewis on Williams

As for the man: he is about 52, of humble origin (there are still traces of cockney in his voice), ugly as a chimpanzee but so radiant (he emanates more love than any man I have ever known) that as soon as he begins talking whether in private or in a lecture he is transfigured and looks like an angel. He sweeps some people quite off their feet and has many disciples. Women find him so attractive that if he were a bad man he could do what he liked either as a Don Juan or a charlatan. He works in the Oxford University Press. In spite of his "angelic" quality he is also quite an earthy person and when Warnie, Tolkien, he and I meet for our pint in a pub in Broad Street, the fun is often so fast and furious that the company probably thinks we're talking bawdy when in fact we're very likely talking Theology. He is married and, I think, youthfully in love with his wife still.

C.S. Lewis, The Collected Letters of C.S. Lewis: Volume II, (Letter to Arthur Greeves Jan 30, 1944)

Two spiritual maxims were constantly present to the mind of Charles Williams: "This also is Thou" and "Neither is this Thou." Holding the first we see that every created thing is, in its degree, an image of God, and the ordinate and faithful appreciation of that thing a clue which, truly followed, will lead back to Him. Holding the second we see that every created thing, the highest devotion to moral duty, the purest conjugal love, the saint and the seraph, is no more than an image, that every one of them, followed for its own sake and isolated from its source, becomes an idol whose service is damnation. The first maxim is the formula of the Romantic Way, the "affirmation of images": the second is that of the Ascetic Way, the "rejection of images." Every soul must in some sense follow both. The Ascetic must honour marriage and poetry and wine and the face of nature even while he rejects them; the Romantic must remember even in his Beatrician moment "Neither is this Thou."

C. S. Lewis, Arthurian Torso, "Williams and the Arthuriad" (1948)