Alan Mathison Turing (23 June 1912 - 7 June 1954) was an English mathematician, pioneering computer scientist, and code breaker. He is the inventor of the Turing machine, and his work to break the German codes during World War II made him a national hero in Britian. 
According to an article about him in Time Magazine, Turing lost his religious faith whilst a teenager after a friend died of tuberculosis. He decided then that all phenomena must have a materialistic explanation.
The following is an excerpt from an April 28, 1999 article from BBC News, entitled 'Alan Turing: Father of the Computer':
"Turing was accustomed to being a non-conformist. At boarding school, he refused to adapt and ignored subjects that did not interest him. He was an atheist, and felt marginalised because of his homosexuality."