Then for centuries people thought that the true way to be a Christian was as a monk in a monastery. Later Christians engaged in deep meditation to be mystics. Then there was the movement called Pietism, or Puritanism in England. But that, too changed with time. Everette Kennedy Brown finally concluded that only one thing really characterizes Christians universally and always.
Christians love one another.
We love one another. In all places, in all times, through all sorts of doctrinal changes, through all sorts of lifestyles which now seem strange to us, Christians consistently try at least try to love one another. That's the choice we make. We either choose to love one another. Or we choose not to love one another.