C.S. Lewis, noted author of many books including the Narnia series, was an avowed atheist for many years, until repeated discussions with his friends J.R.R. Tolkien and Hugo Dyson convinced him otherwise.
On September 19, 1931, Lewis wrote about his slow, steady progression in faith.
“I have passed from believing in God to believing in Christ. My long walk with Dyson & Tolkien had a great deal to do with it.”