A Mighty Fortress

"There are a score of great religions in the world, each with scores or
hundreds of sects, each with its priestly orders, its complicated creed and
ritual, its heavens and hells. Each has its thousands or millions or
hundreds of millions of "true believers"; each damns all the others, with
more or less heartiness -- and each is a mighty fortress of Graft."
- Upton Sinclair, The Profits of Religion, 1927