A former evangelist and close colleague of Billy Graham who has authored the book Farewell to God: My Reasons for Rejecting the Christian Faith (Toronto: McClelland & Stewart, Inc.:1996). Templeton pursued a career as a minister and evangelist back in the 1940s and 1950s in close collaboration with Billy Graham. However, unlike Graham he retained a strong spirit of intellectual inquiry, which led him to investigate more closely the claims of the Bible. His studies led to doubts, which eventually led him to leaving the ministry and the Christian faith. Templeton now describes himself as an agnostic and a humanist.
There's a related article on Templeton in the Winter 1997/98(?) issue of Free Inquiry.