Jesus' teachings turned the world upside down. He told people to love each other, no matter who they were. That sounds good on the surface, but it can be extremely challenging to live out in everyday life. From the very first moment of its existence, the church struggled with this basic principle. People who had been enemies for generations were now asked to love each other. Jews loving Gentiles? Men treating women with respect? Owners honoring workers? Rich people equal with the poor? Emperial citizens sharing with barbarians? You've got to be kidding. Sound familiar? After 19 centuries we...