Republic (Plato)

While visiting the Piraeus with Glaucon, Polemarchus tells Socrates to join him for a romp. Socrates then asks Cephalus, Polemarchus, and Thrasymachus their definitions of justice. Cephalus defines justice as giving what is owed. Polemarchus says justice is "the art which gives good to friends and evil to enemies". Thrasymachus proclaims "justice is nothing else than the interest of the stronger". Socrates overturns their definitions and says that it is to one's advantage to be just and disadvantage to be unjust. The first book ends in aporia concerning its essence.