John Rawls's Trick for Designing a Fair Society

John Rawls published A Theory of Justice in 1971 with one durable thought experiment at its center. Before you set the rules of a society, he proposed, step behind a hypothetical screen he called the veil of ignorance. On the other side, you have no idea who you will be in that society — not your race, not your gender, not your wealth, not your parents, not your talents, not your religion, not even the era you'll live in.

From that position, Rawls argued, no rational person would design a system that crushes any single group, because they might be the ones crushed. They would refuse coin-flip gambles like "50% chance of being a billionaire, 50% chance of being a slave" because the downside is too catastrophic. They would, he said, end up choosing two principles: equal basic liberties for everyone, and economic inequalities allowed only when they actually improve the position of the worst-off.

The move is older than Rawls. Immanuel Kant's categorical imperative — act only on rules you could will to be universal law — runs on the same engine. So does the children's heuristic of letting one kid cut the cake and the other choose the slice. Strip out who-gets-what before you set the rules, and a lot of self-serving arguments evaporate.

The most common objection is that real humans are not purely rational and not really risk-averse in the extreme way Rawls assumed. Robert Nozick, his Harvard colleague, argued that Rawls had quietly smuggled left-leaning intuitions into the setup. But the experiment doesn't have to be fair to be useful. Use it on any policy debate — taxes, prisons, school funding, immigration — and notice how often your position depends on knowing in advance which side of the rule you'll be standing on.