Love your enemies. What does this mean? How is it to be applied?

Jesus told us to love our enemies. What does this mean? How is it to be applied? How do you define 'enemy'? Should we let our enemies live with us? Should we let enemies be part of our church communities? How does blessed are you when you are persecuted for righteousness sake relate to all this?

Josephine Butler – a nineteenth century Christian who advocated for the oppressed and outcast

There is a weak and prostrate figure lying at our door. Her hands are on the threshold, flung forward in mute appeal. On one side of the door are the powers of hell. On the other side, in their safe dwelling place, the selfish sleepers to whom the pale cold hands appeal in vain.