I think all the great religions of the world - Buddhism, Hinduism, Christianity, Islam, and Communism - both untrue and harmful. It is evident as a matter of logic that, since they disagree, not more than one of them can be true. With very few exception, the religions which a man accepts is that of the community in which he lives, which makes it obvious that the influence of environment is what has led him to accept the religion in question.

Preface - Why I Am Not a Christian (1927)