Mere Christianity is often described as a good book for an unbeliever to read if he is seeking to establish a rational basis for belief first in God, second in religion and thence in Christianity. The book is adapted from a series of radio lectures by C.S. Lewis author of the Chronicles of Narnia. These were originally broadcast by the BBC in 1943 while Lewis taught at Oxford University. 
- Lewis, C. S. (2001). Mere Christianity: a revised and amplified edition, with a new introduction, of the three books, Broadcast talks, Christian behaviour, and Beyond personality. [San Francisco]: HarperSanFrancisco. ISBN 0-06-065292-6.
- http://www.bbc.co.uk/religion/religions/christianity/people/cslewis_16.shtml The only surviving footage of C.S. Lewis's broadcast talk