Chapter XIV: Checkmate.
Lewis spent a year "reading" English at the university and then became a lecturer in Philosophy at one of the colleges. All of the authors that he found the best were Christian, but he brushed that off as accidental, or a sign that they were part way to the right philosophy, but didn't quite get it. He also began to make friends who were Christian (Including Tolkien). He lists three things that he "discovered" or that God unveiled to him that forced a huge change in his basic outlook. They are too complicated to explain here (not even sure I could0, but combined they forced him to reexamine his underlying beliefs and his actions. It was not an easy time for him. "Amiable agnostics will talk cheerfully about 'man's search for God." To me, as I then was, they might as well have talked about the mouse's search for the at." (p196)
He came to realize that this new philosophy had to be lived. And one night in his room he admitted that God was God and knelt and prayed to God, the "Most defected and reluctant convert in all England."