Imagine a world without rules: nothing is illegal, nothing is immoral, everyone is absolutely free. This might sound like a utopia to you. But according to 17th century British philosopher, Thomas Hobbes, it would actually be your worst nightmare.

Hobbes called this hypothetical time, with no rules to govern our behavior, the state of nature, and he described life there as “solitary, poor, nasty, brutish, and short.”

And he was probably right. The land of Do-As-You-Please sounds great until you realize that everyone else is also doing as they please. That's when you find out that you have an abundance of freedom, but you do not have any security. Because when everyone’s constantly watching their backs, whoever is the biggest bully will be able to dominate simply by fear and aggression. And even if you happen to be the biggest bully, life's not gonna be any better. Because when enough weaker bullies get together, even the strongest can be overthrown.

So this type of system - a sort of anti-system without rules and without order - is a terrible way to live. And Hobbes pointed out that rational people would want to change the system. They’d trade in some of their natural freedoms in exchange for the security offered by civil society. The key to saving the world from chaos, he said, was a contract.

Hobbes didn't think there was anything deeply real about morality. It's not written in the stars or waiting to be discovered by reason or handed to us on stone tablets by the divine. Morality, he believed, is not primitive or natural. Instead, Hobbs proposed, anytime you get a group of free, self-interested, rational individuals living together, morality will just emerge.

Because free, rational, self-interested people realize that there are more benefits to be found in cooperating than in not cooperating.

Like, say, I have an avocado tree growing outside of my house. I consider it mine and I can take all the avocados I want from it. You have a mango tree and you can take all the mangoes you want. But sometimes avocado havers grow tired of avocados and mango havers grow tired of mangoes. This might actually be a bad example, because, is there any such thing as too much guacamole?

But sometimes you just really want a mango smoothie. And in the state of nature - where there are no rules - the only way for me to get a mango is to steal it. And the same goes for you and my avocados.

So we found ourselves living in a world where we steal from each other. Which means that both of us are always on edge and we see each other as enemies. But remember we're rational, so we find a better way. We make an agreement. We promise not to steal from each other and we promise to trade avocados for mangoes. Now we have more security and more interesting diet.

What we have created is a contract: a shared agreement. And suddenly morality is born. This view espoused by Hobbs and followed by many today is known as contractarianism. Contractarians say that right acts are those that do not violate the free, rational agreements that we’ve made. And we make these agreements because we think they'll make our lives better. So basically, we trade in some freedom for the benefits that come out of cooperative living.

Avocado-for-mango contracts are pretty straightforward. We both want something and we make an explicit contract that we both believe will result in us being better off. But some contracts aren't so obvious. We're also bound up in a lot of implicit contracts, ones that we've never actually agreed to but sort of find ourselves in. For instance, natural-born citizens of the United States never agreed to follow the law of the land. Immigrants who become citizens do - they have to engage in an explicit contract as part of the citizenship process.

But for the rest of us, we are expected to follow all sorts of rules that we never agreed to follow. Now if you tried to explain to the cop who pulled you over that you never agreed to the speed limit so you're not bound to follow it, pretty sure you're gonna get a ticket anyway.

And that might seem really unfair to you. But contractarians will tell you that it's not. Because you reap all kinds of benefits from being a part of this system. You get to drive on safe roads, drink clean water and if your house catches on fire, people will show up and do their best to put it out.

Rights imply obligations, by Hobbs thinking, so when you take from the common pot - by enjoying the goods that the system provides - you are also expected to pay in.

That's what happens when you pay taxes and when you show up for jury duty and when you accept the punishment for violating the rules ... even rules that you disagree with.

So, contracts are pretty brilliant way for making society not just survivable, but possible. They save you from the situation that Hobbes described as “war of all against all” and puts you in this idyllic land where everyone cooperates. But, can you really count on cooperation? To explore that question let's head over to the Thought Bubble for some flash philosophy.

In the 1950s, Canadian mathematician, Albert W Tucker, formalized an idea that had originally been posed by American game theorists, Merrill Flood and Melvin Dresher. Since then, many versions of this dilemma have been presented, but Tucker’s scenario goes like this.

You and your partner in crime are both arrested and put in separate rooms for interrogation. The prosecution doesn't have enough evidence to convict you for your main offense. The best they can hope for is to give you each a year in prison on a lesser charge. So, the prosecution offers you each a deal. If you rat out your partner, they’ll let you go free. But now you and your partner face a dilemma. If you both remain silent, you know you won't get any more than a year in prison. But if you're enticed by the thought of doing no time at all, all you have to do is squeal and you'll go free while your partner does three years.

The problem is, enticed as you are by the offer, you know that your partner is thinking the same thing. And if you each give up the other, then the prosecution will have enough evidence to send you both away for two years. So now you think, “no, it's better to stay silent.” That way you'll only get the one year as long as you can count on your partner to reason the same way.

But what if he doesn't? What if you stay quiet and your partner's the rat? Well, that means you're doing three long years while he gets away scot-free. Facing that unpleasant prospect, if you're both rational agents, you'll be drawn to the conclusion that looking out for yourself is the best option because it carries with the prospect of either or 0 or 2 years rather than the one or three years that you might get you stay silent. Thanks, thought bubble.

The prisoner's dilemma shows us some interesting wrinkles in contractarianism. Even though it was rational for both prisoners to squeal, they actually would have been better off if they could count on each other to stay quiet. Cooperation pays but only when you trust your fellow contractors to keep their agreements. This is why a lot of defection occurs among strangers. Defection is where you break the contract you're in - whether you agree to be in it or not - and you decide to look after your own interests, instead of cooperating.

For example, the next time you're driving during rush hour you will see rampant defection. Instead of following the rules, waiting their turn, and merging when they're supposed to, people will speed down the shoulders and try to sneak up to the head of the merge lane which ends up slowing down everybody. But you see much less defection among people who know each other. Because when you flagrantly violate a contract among people you know, it comes with a heavy social cost.

There's a special kind of moral outrage for somebody who freely makes an agreement they didn't have to make, and then violates it, because our whole society is built on the trust that people will keep their word.

But there's another important part of this theory, one that we haven't mentioned yet. And that is, in order for a contract to be valid the contractors must be free.

You can't force someone into a contract. And the contractors must be better off in the system that the contract makes possible, then they would be outside of it

Sure, there are probably some rules that don't work in your favor all the time, but the system, overall, must make your life better than if you were on your own.

So, contractarianism necessarily rules out things like slavery. Any given person will always be better off outside a system that in slaves her. So that type of system could never be legitimate even if it's agreed upon by the majority of the group.

And maybe you've noticed something else about this moral theory, something that's distinct from, say, the divine command theory or Kantianism or even utilitarianism. With contractarianism, there is no morality until we make it up.

There is nothing fundamentally “real” about it. But it becomes real, as soon as you and I agree that it is, because once we agree to particular rules, they become real, and binding.

So in a way, contractarianism is the most permissive of the moral theories we've looked at. Morality is determined by groups of contractors. So whatever they agree to goes. Which means, of course, morality can change.

If, as a group, we change our minds, we can simply modify the contract. Which is exactly what happens, explicitly, when we change laws, and implicitly, with shifting social mores.

Contractarianism is still pretty rigid in some ways. If you take on an obligation, you have a duty to keep it. This theory starts with the assumption that we get to choose what responsibilities we incur. So, we're all held to a high standard for keeping the agreements we choose to make.

Next time we're going to conclude our unit on moral theory with a look at virtue theory.

Today, though, we learned about contractarianism. We talk about Hobbs's state of nature and the implicit and explicit contracts. We learned about the prisoner's dilemma and the benefits and costs of violating contracts.

Crash Course Philosophy is produced in association with PBS Digital Studios. You can head over to their channel to check out a playlist of the latest episodes from shows like, It's Okay To Be Smart, Physics Girl, and Shanks Effects.

This episode of Crash Course Philosophy was filmed in the Doctor Cheryl C. Kinney crash course studio with the help of all these awesome people. And our equally fantastic graphics team is Thought Café.