“Do not be conformed to this world” is one of the most grating verses of the Bible to many modern ears, yet it is not just a Pauline one-off. The nonconforming set-apartness of God’s people is a major theme of the whole Bible. But it’s an unpopular idea these days, both for Christians who wish they could blend in and for nonbelievers pressuring religious institutions to compromise on their different-ness.