The 18th century English cleric and theologian John Wesley was troubled by a paradox that emerged as his teaching spread. He, like other Protestant thinkers stretching back to Calvin, taught that one could honor God through hard work and thrift. The subsequent burst of industry and frugality generated by Wesley's message improved the lot of many of his working-class followers and helped advance capitalism in England. But "wherever riches have increased, the essence of religion has decreased in the same proportion," Wesley observed, and subsequently pride and greed are growing more common, he complained. The emergence of what Max Weber...