" A Rabbi gathered together his students and asked them: ‘How do we know the exact moment when night ends and day begins?’ ‘When it’s light enough to tell a sheep from a dog,’ said one boy. Another student said: ‘No, when it’s light enough to tell an olive tree from a fig tree.’ ‘No, that’s not a good definition either.’ ‘Well, what’s the right answer?’ asked the boys. And the Rabbi said: ‘When a stranger approaches, and we think he is our brother, and all conflicts disappear, that is the moment when night ends and day begins. "

― Paulo Coelho , Like the Flowing River