There is an old Hassidic tale in which a rabbi asks his pupils how they could tell when the night ends and day begins.
“Could it be,” one of his students asked, “when you see an animal in the distance and can tell whether it is a sheep or a dog? "No,” answered the rabbi.
Another student asked, “Is it when you look at a tree in the distance and can tell whether it is a fig tree or a peach tree?” “No,” the rabbi patiently replied.
“Tell us then,” the students asked, “when does night end and day begin?”
The rabbi replied, “It is when you can look on the face of any man or woman and see that it is the face of your sister or your brother. If you cannot see this, it is still night.”