What Do We Owe to Each Other? A Guide to Contractualism

Imagine you and your friend both want the last slice of pizza. You could just grab it, but instead you pause and think: Could I justify taking it to her? If she’d be hungry too, and there’s no good reason you should get it instead of her, you probably shouldn’t take it. That moment of hesitation—wondering whether you could explain yourself to someone else—is the heart of a philosophical idea called contractualism.

This isn’t about actual contracts you sign. It’s about a way of thinking about right and wrong. The basic idea, from philosopher T.M. Scanlon, goes like this:

An act is wrong if it would be forbidden by any set of rules that no one could reasonably reject.

That’s a mouthful. Let’s unpack it.

The Central Puzzle: What Makes Something Wrong?

Here’s the strange thing philosophers noticed: when you say something is wrong—like stealing, lying, or hurting someone—you’re not just saying “I don’t like that.” You’re making a claim that the other person ought to understand. You’re saying there’s a reason they should agree with you.

But what if they don’t? What if someone thinks it’s fine to break a promise if it benefits them? How do you prove they’re wrong?

Utilitarians (a different group of philosophers) say: look at the consequences. An action is wrong if it produces less happiness overall than the alternatives. If breaking a promise makes five people happy and only one person sad, maybe it’s okay.

Many people find this unsatisfying. It feels like it ignores something important about each individual person. But what’s the alternative?

Contractualism offers a different answer: instead of adding up everyone’s happiness, we should ask what rules each person could reasonably accept. This shifts the focus from “what makes the best outcome” to “what can I justify to you?”

The idea of a “social contract” has been around for a long time. But there are two very different ways to understand it.

Contractarianism (from Thomas Hobbes) says: morality is a deal we make because it benefits each of us. I agree not to steal from you if you agree not to steal from me. We’re both better off. This is based on self-interest.

Contractualism (from Jean-Jacques Rousseau and later Scanlon) says: morality isn’t just a bargain. It’s about recognizing that other people matter in the same way you do. You don’t just want a good deal for yourself—you want to live with others on terms of mutual respect.

Think of the difference this way. Under contractarianism, you might say: “I’ll stop cutting in line if everyone else does too—it’s better for everyone.” Under contractualism, you might say: “I shouldn’t cut in line because I couldn’t justify to the people behind me why my time matters more than theirs.”

This second motivation—wanting to justify yourself to others, not just to get what you want—is crucial for contractualism.

Why Not Just Add Everything Up?

Imagine your school has to decide whether to cancel a fun field trip to save money. The principal calculates: the trip would make 200 students happy, but canceling it would disappoint them. However, the money saved could buy new books that would help future students for years. The utilitarian says: add up all the happiness and choose whatever creates the most.

But what if canceling the trip would really hurt one particular student who has been looking forward to it all year? The contractualist says: we shouldn’t just add everyone’s happiness together and let the majority win. We need to ask whether the student could reasonably reject the rule that lets the principal cancel the trip.

This is called the “separateness of persons.” Each person has their own life to live. You can’t just treat people like buckets that you fill with happiness and then add up. One person’s suffering isn’t cancelled out by another person’s joy—not in the simple way utilitarian math suggests.

Can You Really Avoid Adding Things Up?

Here’s where it gets tricky. Picture this famous thought experiment:

The Rocks. Six swimmers are trapped on two rocks as the tide comes in. Five swimmers are on one rock, one swimmer is on another. You can only reach one rock in time. Should you save the five or the one?

Most people say: save the five. That’s obvious, right?

But the contractualist has a problem. The one swimmer can say: “I’ll die if you don’t save me!” Each of the five can say the same thing: “I’ll die if you don’t save me!” All six have the same complaint. So how do you decide?

The utilitarian just adds: five deaths are worse than one. But the contractualist can’t add like that, because each person’s complaint is individual. If you try to argue that the five together have a stronger complaint, you’re doing exactly the kind of adding up contractualism is supposed to avoid.

Some contractualists bite the bullet and say: maybe you should flip a coin. That gives everyone a fair chance. But many find this deeply unsatisfying. Saving five people instead of one seems clearly right, not a toss-up.

This is a live debate. Philosophers are still arguing about whether contractualism can handle cases like this without collapsing into the kind of thinking it was meant to replace.

What Counts as a Reason to Reject a Rule?

One of contractualism’s strengths is that it allows many different kinds of reasons to reject a rule—not just “this hurts me.”

Imagine a rule that distributes benefits based on race. Even if the burdens are the same as a random distribution, you can reject the racist rule for a different reason: it disrespects you. It says your race matters in a way it shouldn’t. The way the burden is imposed matters, not just how much burden there is.

This flexibility helps contractualism handle cases that trip up other theories. But it also creates a problem: if you can reject rules for all sorts of reasons, couldn’t you just say “I reject this rule because it’s wrong”? That would be circular—using the very thing you’re trying to explain.

Contractualists have an answer. “Because it’s wrong” isn’t a reason that feeds into the contractualist machinery. Wrongness is what comes out of the machinery, not what goes in. Your reason for rejecting a rule has to be something specific to you—something about how the rule affects you or treats you.

Does Contractualism Demand Too Much?

Imagine two very different perspectives:

Person A is starving. They can reasonably reject any rule that lets you keep your extra money instead of buying them food.

Person B wants to live their own life. They can reasonably reject any rule that forces them to give up everything they own to help strangers.

Who wins? Nagel, another philosopher, argues that in today’s world, every possible rule about helping others will be reasonably rejected by someone. The starving person rejects the rule that lets you keep your money. The comfortable person rejects the rule that takes all their money. There’s no rule that works for everyone.

Contractualists have different responses. Some say: yes, morality is extremely demanding. If you can save a life by making a moderate sacrifice, it’s wrong not to. Others try to find a middle ground—a rule that respects both the person in need and the person being asked to give.

This isn’t abstract. Think about charity appeals you’ve seen. A child dies every few seconds from preventable diseases. For the cost of a few video games, you could save a life. If you don’t, are you doing something wrong? Contractualism forces you to ask: could you justify your choice to that child? To their parents?

Animals, Future People, and the Limits of the Theory

Contractualism faces two big challenges about who’s included.

Animals. Can you justify your actions to a dog? A cow? A bird? They can’t understand reasons or make agreements. So does contractualism mean we can do anything to them? Scanlon admits that contractualism only covers “what we owe to each other”—to beings capable of mutual justification. He suggests animals might be protected by a different part of morality. But critics say this is a weakness: torturing animals is wrong because of the suffering, not because of some abstract principle about justification.

Future people. Can future generations reasonably reject rules we make today? They don’t exist yet, so they can’t agree to anything. But our actions—like burning fossil fuels or creating nuclear waste—will affect them enormously.

Here’s a stranger puzzle. Imagine a woman, Mary, decides to have a child in winter even though she knows a summer baby would be healthier. It’s slightly inconvenient for her to wait. If she has a winter baby, that specific child will exist, with a painful condition. If she had a summer baby, a different child would exist. The winter child can’t complain, because the alternative was never existing at all. The summer child never exists to complain. So who can reasonably reject Mary’s choice?

This is called the “non-identity problem.” It’s still being debated. Some contractualists argue that even though no specific individual is harmed, Mary shows disrespect to “her future child” in general. Others think contractualism needs to be modified to handle these cases.

Why Does This Matter?

Contractualism isn’t just an abstract theory. It captures something real about how we actually argue about right and wrong.

When you say to a friend, “How would you feel if someone did that to you?”—you’re doing something like contractualism. You’re asking them to see things from another person’s perspective and consider whether they could justify their action.

When you hear someone say, “That’s not fair, why does she get special treatment?”—they’re implicitly asking whether a rule that gives some people special treatment could be justified to everyone.

The idea that morality is about what we can justify to each other—not about following rules blindly or just maximizing happiness—is powerful. It explains why we care about fairness, respect, and being able to look other people in the eye.

Contractualism doesn’t give easy answers. It’s a framework for thinking, not a calculator that spits out right and wrong. But that might be exactly right: moral life is complicated, and we’re still figuring out what we owe to each other.

Appendices

Key Terms

Term	What it does in the debate
Contractualism	The view that wrongness is determined by what principles no one could reasonably reject, rather than by consequences or fixed rules
Reasonable rejection	The test for whether a rule is morally acceptable—you can reject a rule if you have a good reason to object to it from your own perspective
Aggregation	Adding up benefits or harms across different people, which contractualism tries to avoid because it ignores the separateness of persons
Separateness of persons	The idea that each person has their own life and can’t simply be lumped together with others when making moral calculations
Non-identity problem	A puzzle about future people: if our choices determine which specific people exist, can we harm someone who wouldn’t exist otherwise?
Ex ante / ex post	Two perspectives on justification: before you know what will happen to you (ex ante) or after you know (ex post)

Key People

T.M. Scanlon – A contemporary philosopher at Harvard who developed the most well-known version of contractualism. He argues that what matters most in morality is being able to justify yourself to others.
John Rawls – A political philosopher who used a “social contract” idea to think about justice, but more focused on basic political structures than everyday moral choices.
Derek Parfit – A philosopher who argued that contractualism, rule consequentialism, and Kantian ethics might all converge on the same rules, challenging the idea that contractualism is truly distinct.
Thomas Hobbes – An earlier philosopher whose “contractarianism” grounded morality in mutual self-interest, rather than mutual respect.

Things to Think About

If contractualism is about justifying yourself to others, what happens when someone is unreasonable? If a classmate rejects every rule you propose just to be difficult, does that mean the rule is unjustified?
The rocks example (saving five vs. one) seems to show that sometimes we do need to add things up. Can you think of a way to justify saving the five without adding up individual complaints? Or should we accept the coin-flip?
Does the obligation to help strangers really require you to give up everything you own? Where would you draw the line between reasonable sacrifice and unreasonable demand? How would you justify that line to someone who is starving?
If contractualism can’t easily explain why torturing animals is wrong, is that a fatal flaw? Or is it okay for a theory to only cover part of morality?

Where This Shows Up

Arguments about fairness – When someone says “that’s not fair,” they’re often implicitly asking whether a rule could be justified to everyone affected.
Political debates – Discussions about what rights people have often rely on the idea that certain policies couldn’t be justified to everyone.
Friendship and relationships – When friends argue, they often appeal to what each can reasonably expect from the other—exactly the kind of reasoning contractualism describes.
Debates about climate change – Questions about what we owe future generations are directly addressed by contractualist thinking about future people.