Why have societies that were once overwhelmingly Christian become so secular? We think we know the answer, but Alec Ryrie argues that people embraced unbelief much as they have always chosen their worldviews: through their hearts more than their minds. Looking back to the crisis of the Reformation and beyond, Ryrie shows how, long before philosophers started to make the case for atheism, powerful cultural currents were challenging traditional faith. Protestant radicals defended their faith by redefining it in terms of ethics, but this set in motion secularizing forces that affected both the Church and unbelievers.