Like Bloom Lewis came from a Christian family, Northern Irish Protestants, but he lapsed. However, unlike Bloom who had a powerful moment of revelation, Lewis' path to God came through a combination of influences before a revelatory moment.
Lewis, who returned to Christianity while a philosophy lecturer at Oxford, was never a materialist. He was an idealist, a believer in an ultimate reality, an absolute, accessible by reason and known non-personally.
But his path to faith came from the transformation of his idealism and his shedding of prejudices, under friends' influence. Barfield helped him shed his anti-mediaeval prejudices, showing him that mediaeval should not be a term of disparagement, because ideas can go from fashion for bad reasons. Another friend,Cogshill, challenged his anti-Christian prejudices that Christians were stupid and uneducated, for Cogshill was one of the most intelligent and well informed people Lewis had ever known. A third friend, Tolkien, made him face up to his anti-Catholic prejudices learned from his Northern Irish background, which taught him never to trust a papist.
But there were writers whom he admired. G.K.Chesterton, Lewis considered the cleverest man alive, except for his Catholic faith.He was later to come to see that Chesterton's wisdom was integrally connected to his Catholicism. Reading Chesterton's Everlasting Man, a life of Christ, shook Lewis to the core. Moreover the Anglican poet George Herbert, who viewed life from the perspective of the Christian mythos, inspired but annoyed Lewis. Could he not do without the Christianity! But Lewis began to feel that religious writers were somehow more interesting and deeper than non-religious ones, but he hung on to his non-belief, fighting a struggle with the presence that was growing closer to him and more intense.
Another moment unsettled him. Having read Frazer's Golden Bough, which spoke of the Myth of the Dying and the Rising God, he heard a dyed in the wool atheist academic say that it was a rum thing, but that it seemed to have happened once. Again, Lewis' world-view became unsettled, but he persisted in his rejection of Christianity. Non-belief was becoming hard work.
The final moment came when alone in his study at Oxford he yielded to the presence that had been calling him. He had for a while become convinced that he was wearing an emotional suit of armour against the call of the divine presence, than in that lonely moment he surrendered, transformed his idealism and admitted that God was God. There were still moves to be made. He had at that moment converted to theism, general belief in God, but he was later to decide for Christianity. His book Surprised by Joy,speaks of the joy that comes with belief. This is not a state of excitement but of fulfillment greater than the travails of the moment. Strangely, having scorned Herbert's use of the Christian myth in literature, Lewis' transformation led to his using it as the literary theme of the Narnia series, quite a turn around.
[See Surprised by Joy, chapter 14]