When students first learn about Rawls’s difference principle, they often assume Rawls intends the principle to be applied directly to every transaction. I can’t accept a pay raise unless this somehow indirectly benefits full-time janitors. But Rawls doesn’t intend for the principle to work that way. Rawls thinks that rules–when they are properly internalized and when people mostly comply with them–have systematic utility or disutility. For Rawls, the difference principle is a standard not for individual transactions, but for entire systems of property right rules along with the bigger political structures in which they are embedded.

So, by analogy, we might say that the point of the game of football is ultimately to have fun. But referees are not supposed to judge individual moves on the field according to whether they maximize fun–if referees did that, the game wouldn’t work. It wouldn’t be much fun. If referees just changed the game on the fly with the goal of maximizing fun, it would mess up the game. Part of what produces the fun is the tension and challenge created by having set rules. The rules can be changed for various reasons (to make the game more fun, safer, faster, or whatnot), but not on the fly.

So it goes for Rawls. The difference principle isn’t itself meant to be a rule that governs individual property exchanges, but rather a rule of recognition by which we determine which property (and other) legal rules are best.

Something like this is going in Locke and Nozick, too. Locke and Nozick ask what could possibly justify the institution of property. In a world in which nothing is owned, everyone has a permission right to use anything and go anywhere she pleases. When someone first encloses a field and says, “This is mine!,” he seems in the first instance to just limit and reduce everyone else’s freedom. As Rousseau would ask, why should anyone play along with that?

Locke’s answer (and Nozick toys with a similar answer) is that appropriating stuff as one’s own is permissible provided one leaves enough and as good for others. Exactly what the rules are for original appropriation is a complicated question, and neither gives us a full theory. Still, Locke and Nozick both add that the “enough and has good” standard is easily met: A bit of land might be 10,000 times more productive when owned and farmed then when unowned, and under the right conditions, people other than the owner end up sharing in the surplus. Sure, privatization in the first place reduces others’ liberty, but they are more than compensated for it by becoming much richer. (In a sense, privatization reduces people’s negative liberty to just go wherever they please, but increases their positive liberty by imbuing them with more power to achieve their ends.)

As David Schmidtz points out, most contemporary Americans didn’t appropriate any land for themselves, but they are vastly better off that the people who first got here and did the original appropriating. I’d have to be misinformed or masochistic to want to trade my lot with that any of the first human settlers of the Americas, or even any of the first white settlers. Schmidtz adds: because of the problem of the tragic commons, it might even be that the imperative to leave enough and as good for others requires us to parcel and privatize.

The Lockean Proviso is itself most plausible when seen as part of a systematic justification of private property. It’s not plausible if it’s meant to govern every individual transaction. It doesn’t seem plausible that I am allowed to homestead some land in Montana only if everyone else benefits from my homesteading. That’s probably an impossibly strict standard. Rather, I’m justified in appropriating the land provided I play by the proper appropriation rules in the game “private property,” and the game of “private property” is itself justified because it systematically leads to certain results.

But then the questions are: Which private property game is best? Why? What count as good enough results to justify the game? Rawls, Locke, and Nozick think that some sort of private property game will be justifiable, and they have both deontological and consequentialist arguments on behalf of the game. But Nozick and Locke have less strict consequentialist standards than Rawls; Rawls thinks that to be justified, a private property system has to perform better (in one particular way) than Nozick or Locke do.

By analogy, if Nozick and Rawls were debating the best rules for football, they might make different trade-offs between safety and speed. They both agree we should play football, but they disagree about the standards for judging the best set of rules for football. They disagree about some of the empirical facts. As a result, they disagree about what’s the optimal set of on-the-ground rules.

Crude libertarians often say that advocates of social justice believe the government can steal your stuff to feed people. Well, perhaps all government taxes do turn out to be theft. But it’s worth noting the Rawls doesn’t see himself as advocating theft. Rather, see the debate between Nozick and him as this: They disagree on what the proper standards are for judging the game of private property. In part, because of that (but also because of empirical disagreements about how institutions work), they disagree about what set of private property rules ends up being justified. If Nozick is right, then the entitlement theory is right. In a just world, where people always followed the entitlement theory, government that taxed me to feed the homeless would be stealing from me. If Rawls is right, then some other account of property rights is correct, and when the government taxes me to feed the homeless, that doesn’t count as theft, because the government is entitled to the money and I am not.