How did Christianity stand out in the ancient world? What made it different from other religions? In the early 20th century, the dominant theory was that Christianity was just one of many new religions (the Manicheans, the mystery cults, the cult of Mithras, etc) which happened to have better PR and more Machiavellian leadership. That scholarship has been discredited these days, but what then is the truth? Why did Christianity take off in so spectacular–albeit halting–a fashion?