Plato 
Euthyphro [PDF ebook] 

Euthyphro, by Plato, is a Socratic dialogue whose events occur in the weeks before the trial of Socrates (399 BC), between Socrates and Euthyphro. The dialogue covers subjects such as the meaning of piety and justice.
The Euthyphro dialogue occurs near the court of the archon basileus (king magistrate), where Socrates and Euthyphro encounter each other; each man is present at the court for the preliminary hearings to possible trials (2a).
Euthyphro has come to present charges of murder against his own father who, after arresting one of his workers for killing a slave from the family estate on Naxos Island, tied him and threw him in a ditch where he died of exposure to the elements without proper care and attention (3e–4d) while Euthyphro's father awaited to hear from the exegetes (cf. Laws 759d) about how to proceed. Socrates is astonished by Euthyphro's confidence in being able to prosecute his own father for the serious charge of manslaughter, despite the fact that Athenian Law allows only relatives of the dead man to file suit for murder. (Dem. 43 §57) Euthyphro dismisses the astonishment of Socrates, which confirms his overconfidence in his own critical judgment of matters religious and ethical.
In an example of Socratic irony, Socrates says that Euthyphro obviously has a clear understanding of what is pious or holy and impious or unholy. Because he is facing a formal charge of impiety, Socrates expresses the hope to learn from Euthyphro, all the better to defend himself in the trial, as he himself is being accused of religious transgressions.
Euthyphro says that what lies behind the charge of impiety presented against Socrates, by Meletus and the others, is Socrates' claim that he is subjected to a daimon, (divine sign) which warns him of various courses of action. (3b) From the perspective of some Athenians, Socrates expressed scepticism of the accounts about the Greek gods, which he and Euthyphro briefly discuss, before proceeding to the main argument of their dialogue: the definition of "piety". Moreover, Socrates further expresses critical reservations about such divine accounts that emphasise the cruelty and inconsistent behaviour of the Greek gods, such as the castration of the early sky-god Uranus, by his son Cronus; a story Socrates said is difficult to accept. (6a–6c)
After claiming to know and be able to tell more astonishing divine stories, Euthyphro spends little time and effort defending the conventional, Greek view of the gods. Instead, he is led to the true task at hand, as Socrates forces him to confront his ignorance, by pressing Euthyphro for a definition of "piety"; yet, Socrates finds flaw with each definition of "piety" proposed by Euthyphro.(6d ff.)