C. S. Lewis

C. S. Lewis was a medievalist at Oxford and, for the first half of his life, a convinced atheist. He was argued out of it slowly and against his will – he called himself the most reluctant convert in all England – helped on his way by Chesterton's Everlasting Man, which made the Christian story look strangely like the truth, and by a long night's walk in September 1931 with J. R. R. Tolkien, who persuaded him that the myth of a dying and rising god might be the one myth that had also happened.

Having crossed over, he became the plainest and most persuasive Christian voice of the century – first on wartime radio, then in the little book those talks became, Mere Christianity. Its opening move is an argument you can watch happen in any quarrel: when two people fall out, each appeals to a standard of fair play they both expect the other to know, a Law of Human Nature they did not invent and cannot quite escape. Where does that law come from, he asks, and follows the question upward.

His deepest book is the shortest. The Abolition of Man defends the existence of a real moral order, which he borrows a Chinese word to call the Tao – the body of first principles about good and evil that every great civilisation, pagan and Christian alike, has recognised. Cut men off from it, teach them that all values are merely feelings, and you produce men without chests: heads and appetites with nothing trained in between, and then you are astonished to find them cowards and cads. Worse are the Conditioners, the planners who would step outside the Tao to remake human nature to a design of their own – and who, in mastering man, would abolish him, since nothing would be left to say their design was wrong. Lewis wrote it in 1943, watching one such experiment burn across Europe.

He could be playful about all this – The Screwtape Letters is a senior devil's correspondence course in damnation, and one of the funniest religious books ever written. And he could be broken by it: when his wife died of cancer, the great apologist sat down and wrote A Grief Observed, the raw notebook of a believer whose faith has just been kicked out from under him, unsure whether God is absent or worse.