Book 1: What is Justice?

The dialogue opens at the Piraeus, the port of Athens, during the festival of Bendis. Socrates is detained on the road by Polemarchus and brought to his father Cephalus's house. The old man's reflection on aging is the first move: wealth, Cephalus says, is good chiefly because it lets the just sleep at night without fear of debts unpaid to gods or men. Socrates seizes the implicit definition — justice is paying what's owed — and immediately tests it: should you return a weapon to a friend who has gone mad? Cephalus excuses himself to attend to sacrifices, and the argument passes to Polemarchus, who refines the definition to giving each what's owed, then to helping friends and harming enemies.

Socrates dismantles it. We misjudge who is friend and enemy. A doctor helps the sick because his craft serves them, not because they are his friends. Justice, treated as a craft, cannot include harm to anyone — to harm a man is to make him worse, and no genuine craft makes its object worse. The argument has moved from common-sense morality to a far stranger claim: the just person does no harm, period.

Then Thrasymachus the sophist erupts. He is angry that Socrates is asking instead of answering, and he gives his definition with maximum force: justice is the advantage of the stronger. The ruling class makes laws that serve itself and calls obeying them just. Socrates pushes back through the craft analogy again: a doctor serves the patient, a shepherd serves the sheep — rulers, if they are truly ruling, serve the ruled. Thrasymachus retreats to a stronger position: injustice on a large scale (tyranny) is more profitable, more enviable, and happier than justice.

Book 1 ends without a settled definition. Socrates admits he has not learned what justice is — he has only argued that whatever it is, it does not benefit the unjust. The book functions as a Platonic prelude: the easy answers are cleared away. The real question — what justice is, and whether it pays to have it — opens Book 2. Modern scholarship (Vlastos, Annas, Cooper) reads Book 1 as the elenchus form of early Plato; Books 2-10 are the constructive answer Plato moved to in his middle period. Read together they show the philosopher learning to build rather than only to question.