What are the limits of human love? Can we love everyone? Or should we only focus on those closest to us? And what happens when our personal loves and commitments come into contact with impersonal questions of justice?
Taking your father to court
The philosopher Socrates is outside the court in Athens. He has been accused of impiety and corrupting the minds of the youth of the city—a charge for which he will soon be executed. As he is idling in the street outside the courthouse, he comes across an earnest young man called Euthyphro. The young man is bringing a charge of murder against his father, something that is all but unthinkable in Athenian society.
The substance of the charge is this. A servant who worked for Euthyphro's father got drunk, and in a fit of anger killed one of the household slaves. Euthyphro's dad took the servant, bound him hand and foot and threw him in a ditch while he decided what to do with him next. Unfortunately, before he could come to a decision, the servant died of hunger.
Socrates is shocked that Euthyphro is taking his father to court. But Euthyphro defends himself as follows:
It is ridiculous, Socrates, for you to think that it makes any difference whether the victim is a stranger or a relative. One should only watch whether the killer acted justly or not; if he acted justly, let him go, but if not, one should prosecute... 
Euthyphro argues that taking his father to court is the good and pious thing to do, even though under Athenian law only the relatives of the dead can press murder charges. Socrates, who is himself being accused of impiety, seizes on Euthyphro's argument about the universality of justice and gets into a long wrangle with the young man about the nature of piety and goodness and justice, tying Euthyphro up in knots.
Plato's dialogue is fascinating for a multitude of reasons. But the central tension with which it begins is one that is with us to this day: what happens when we encounter a conflict between our personal affiliations and loves, and the impersonal demands of justice?