What Is Justice?

In the second book of the Republic, Glaucon tells Socrates he is not satisfied. The previous argument has beaten a sophist into silence, but silencing someone is not the same as showing they were wrong, and Glaucon wants the case made properly. He then constructs the hardest version of the opposing position himself — and it is the best piece of philosophical steelmanning in the ancient world.

The ring

A shepherd named Gyges, the story goes, finds a ring that makes its wearer invisible. He uses it to enter the palace, seduce the queen, kill the king and take the kingdom.

Glaucon's question is not whether this was wrong. It is what any of us would do with the ring. Suppose there were two rings, he says, one given to a just man and one to an unjust man. Is there anyone so iron-willed that they would keep their hands off what was not theirs, when they could take anything from the market without fear, enter any house, kill or free whom they liked? He predicts both men would behave identically — and adds that if you found the just man refusing, onlookers would praise him to his face and think him an idiot in private.

The implied theory is that justice is a compromise. People would prefer to do wrong with impunity and prefer not to suffer it; unable to secure the first, they settle for a mutual agreement not to harm each other, and call it justice. On that account justice is never chosen for itself. It is chosen for its consequences, chiefly reputation, and remove the consequences and it evaporates.

So Glaucon sets Socrates a specific task, and it is stricter than it looks. Do not praise justice for its rewards. Strip a just man of every reward — let him be thought thoroughly unjust, reviled, tortured, and executed — and let the unjust man have every reward including a perfect reputation for virtue. Now show that the just man is better off. Anything less does not answer the challenge.

Plato's answer, and why it is unsatisfying

Socrates' response is the longest detour in philosophy. Justice in a single person is hard to read, he says, so let us look at it written larger — in a city — and then return. Most of the Republic is that city.

The answer that comes back is structural. A just city has three parts — rulers, guardians, producers — each doing its own work and not meddling in the others'. The soul likewise has three parts: reason, spirit and appetite. Justice in a person is the same condition: each part performing its own function, with reason ruling, spirit supporting it, and appetite kept in its place. Injustice is civil war among the parts. On this account the just man is better off in the way a healthy body is better off than a diseased one — and health is not a reward for health.

It is an elegant answer and it has a well-known problem: it may not be about justice. A person whose inner parts are in perfect order might still lie, betray, or exploit. Plato needs psychic harmony to entail treating others rightly, and the argument that it does is the thinnest part of the whole edifice. What he has demonstrably shown is that a certain kind of internal order is good for its possessor. That justice, in the ordinary sense of what we owe each other, is that order remains asserted rather than established.

The same move, made again

Twenty-four centuries later, John Rawls asks a different question with the same instrument. Rather than "would you be just if unobserved?", he asks "what principles would you choose if you did not know who you were going to be?"

Behind the veil of ignorance, you know general facts about societies but not your own place in one: not your class, talents, race, sex, generation, or even your conception of the good life. Then you choose the principles that will govern the society you will inhabit. The reasoning is that principles chosen under those conditions are fair, because nobody can tailor them to advantages they know they have.

Rawls argued that the parties would choose, first, the most extensive equal basic liberties compatible with the same for everyone, and second, that social and economic inequalities are acceptable only if attached to positions open to all under fair equality of opportunity, and only if they work to the greatest benefit of the least advantaged. That last clause — the difference principle — follows from the thought that if you might land at the bottom, you will care a great deal about how the bottom is treated.

The structural kinship with Gyges is exact. Both are information-deletion devices aimed at the same target. Glaucon removes observation to find out whether justice survives without the reputational payoff. Rawls removes identity to find out which rules survive without the self-interested payoff. Both take it for granted that self-interest will corrupt the answer if given the information it needs, and both build a thought experiment to starve it.

The ring is a design question now

Glaucon's thought experiment was hypothetical for everyone who read it for two thousand years. It is not hypothetical now, because unobservability is a property that systems can be built to have or to lack.

Anonymity, deniable channels, actions that leave no attributable trace, aggregate decisions with no identifiable author — each is a partial ring, and every one of them is a design decision somebody made. Glaucon's prediction was that conduct changes when observation is removed, and the accumulated evidence is that he was substantially right, if not as universally as he claimed.

Which puts a sharp edge on the ancient question. If justice only holds under observation, then the design choice about traceability is an ethical choice, made in advance and at scale, for everyone who will use the system. And if Plato is right — if just conduct comes from the ordering of a person rather than from the fear of being seen — then a well-designed audit log tells you nothing about whether the people inside it are just. Both conclusions are uncomfortable, and you cannot have neither.