In the first centurys it called "way of Christ" not Christianity. Name "Christian" was created by Rome prosecution system. So way of Christ mean: you can be safe by his teachings, way thrue him. He literally call himself The Door. Maybe because of this, there a lot of confusion nowadays. I think this confusion was created by porpoise by evil people. So it's mean after Jesus you have ability to be safe thrue love. Before him there was only world way , physical way. For this reason it's call old testament and new testament.
