All that said, Williams seems to misunderstand the keystone of Lewis's imaginative theology, the experience Lewis called "joy." Williams conflates that joy with more prosaic spiritual phenomena -- the psychomachia of everyday life -- that Lewis also evokes.
Here's Williams' take on Lewisian joy:
In fact, in Lewis's telling, you don't do anything to attain joy -- and joy is magic, and it is nostalgia. It's completely unearned. Joy is the lure, not the reward -- the immortal longing that, if followed with a good will, will lead one to God. Lewis, according to his self-described "spiritual autobiography," Surprised by Joy, first experienced it as a toddler:If you look at an extraordinary episode in The Voyage of the Dawn Treader, where Lucy finds herself reading a story in a magical book, when she puts the book down she can't remember the details of the story. She just knows that it's the best thing she's ever read, the most enriching and beautiful thing she's ever encountered. As she's talking to Aslan afterward she says, "Will you tell me that story again?"Aslan says, "One day I shall tell it to you forever." [in fact: "Indeed yes. I will tell it to you for years and years."] It's that kind of moment where you realize that Lewis has got hold of something that very few writers do manage to crystallize, a sense of absolute immersion in the richness of the moment.It comes across in The Screwtape Letters, which still read very well, when the one, old devil says to the younger devil that God's great secret is that he's a pleasure lover at heart. At the heart of it is joy. That's Lewis all over.A good deal of Lewis's life, of course, was marked by enormous stress and great suffering. It's not as if he had an unchallenged life. Some of the emotional force of his writing does come from his being a motherless child, looking back to that sort of magical world before the suffering broke in—and we all have a little bit of that in us.But what he does with it then, instead of making it a cozy, backward-looking thing, he unites it to all of these great moral challenges, the challenge of facing up to yourself, the challenge of going on being faithful in prosaic ways day by day. It's really only by doing the next thing—being faithful in small particulars—that you come to this joy. It's not magic; it's not nostalgia. It's a very fine balance that he deals with remarkably.
Once in those very early days my brother brought into the nursery the lid of a biscuit tin which he had covered with moss and garnished with twigs and flowers so as to make it a toy garden or a toy forest. That was the first beauty I ever knew. What the real garden had failed to do, the toy garden did. It made me aware of nature--not indeed, as a storehouse of forms and colors but as something cool, dewy, fresh, exuberant. I do not think the impression was very important at the moment, but it soon became important in memory. As long as I live my imagination of Paradise will retain something of my brother's toy garden (Surprised by Joy, p. 7).This is the story that Lewis told us for years and years. "What the real garden could not do, the toy garden did." Compare the first real glimpse of heaven, of which our world is said to be just a shadow or copy, in the post-Apocalyptic denouement of The Last Battle:
It is as hard to explain how this sunlit land was different from the old Narnia, as it would be to tell you how the fruits of that country taste. Perhaps you will get some idea of it, if you think like this. You may have been in a room in which there was a window that looked out on a lovely bay of the sea or a green valley that wound away among mountains. And in the wall of that room opposite to the window there may have been a looking glass. And as you turned away from the window you suddenly caught sight of that sea or that valley, all over again, in the looking glass. And the sea in the mirror, or the valley in the mirror, were in one sense just the same as the real ones: yet at the same time they were somehow different---deeper, more wonderful, more like places in a story: in a story you have never heard but very much want to know. The difference between the old Narnia and the new Narnia was like that. The new one was a deeper country; every rock and flower and blade of grass looked as if it meant more. I can't describe it any better than that: if you ever get there, you will know what I mean (The Last Battle, p. 171).That is Lewis' bid to evoke joy in a juvenile audience, and thus spur them to the kind of spiritual work that Williams conflates with the spur. The passage also sets forth Lewis's theory of art (at least the art he valued most and strove to create): by creating a shadow of the real, it gives a glimpse, as if by analogy, of the more-than-real of which our "real" is a Platonic shadow.
Early in Surprised by Joy, after describing more early childhood flashes of the sensation, Lewis ventures a definition:
For those who are still disposed to proceed I will only underline the quality common to the three experiences; it is that of an unsatisfied desire which is itself more desirable than any other satisfaction. I call it Joy, which is here a technical term and must be sharply distinguished both from Happiness and from Pleasure. Joy (in my sense) has indeed one characteristic, and one only, in common with them; the fact that anyone who has experienced it will want it again. Apart from that, and considered only in its quality, it might almost equally well be called a particular kind of unhappiness or grief. But then it is a kind we want. I doubt whether anyone who has tasted it would ever, if both were in his power, exchange it for all the pleasures in the world. But then Joy is never in our power and pleasure often is (Joy, p. 81).Lewis's distinguishing of joy from happiness and pleasure highlights Williams' mistake. The passage in Screwtape Williams cites says nothing about joy: the old devil complains of God, "he's a hedonist at heart," and goes on to cite a panoply of innocent pleasures and sources of happiness that God has provided to humans. Joy is not among them, however. And the pleasures do not have to be earned, any more than joy does. Happiness, yes -- at least, ultimate happiness, the "infinite happiness" that human beings are born to, as a saved soul in heaven assures a visitor from hell in Lewis's dream vision The Great Divorce. Human happiness too, insofar as it's born of the kind of human love that the devils in Screwtape strive ever instant to corrupt. But not joy in Lewis's "technical" sense.
Lewis does write with great psychological acuity, in Screwtape and elsewhere, about the struggle to be charitable, and humble, and courageous, and undeluded by self-love, and so at least capable, if blessed by circumstance, of enjoying an earthly happiness that Lewis would see as a shadow of the "infinite happiness" awaiting those who make of their lives a quest to be fulfilled in death.
But joy is only a signpost, available to all:
but what, in conclusion, of Joy? for that, after all, is what the story has mainly been about. To tell you the truth, the subject has lost nearly all interest for me since I became a Christian. I cannot, indeed, complain, like Wordsworth, that the visionary gleam has passed away...I now know that the experience, considered as a state of my own mind, had never had the kind of importance I once gave it. It was valuable only as a point to something other and outer.While that other was in doubt, the point naturally loomed large in my thoughts. When we are lost in the woods the sight of a signpost is a great matter. He who first sees it cries, "Look!" The whole party gathers round and stares. 'but when we have found the road and are passing signposts every few miles, we shall not stop and stare. They will encourage us and we shall be grateful to the authority that set them up. But we shall not stop and stare, or not much; not on this road, though their pillars are of silver and their lettering of gold. "We would be at Jerusalem" (Joy, p. 238).
For us heathens, Lewis put up a lot of signposts.