The problem of evil is a big theme for a movie, and certainly for a movie based on a comic book, but Batman: The Dark Knight deals with it expertly, and with a message that offers profound support to the idea of human liberty.

It does so in two ways: it supports the view that human beings are capable of cooperating toward the social good, and it shows the unpredictable level of evil that state intervention unleashes. Yes, I know it sounds implausible, but please hear me out.

Consider the Joker, who embodies undiluted, unconscionable evil. The evil that drives him is not limited to a particular sin. It is not greed, for example. At one point in the film, he stacks up all the money he has taken control of from the mob he comes to monopolize. He sets it all on fire in front of the mobsters who stare in shocked amazement. He had previously demanded half their money in exchange for killing Batman, but it turns out that he cares nothing for money. He only wanted to give them pain by persuading them to fork it over. This makes him ungodly scary.

In fact, one is hard pressed to pin any of the seven deadly sins on this guy. He is not really lustful, gluttonous, slothful, wrathful, envious, or prideful — or rather he is all of these things but none of them quite capture what drives him. What he wants is to observe social chaos — and if that means death and destruction, all the better. In order to bring this about, however, he needs one thing more than anything else: he needs power. He will do anything for it and, then, with it.

Additionally, the Joker has a trait that we tend to see in evil people. He carries around with him a peculiar assumption, never really questioned. He assumes that everyone else is secretly as bad as he is. Anything that appears otherwise, he believes to be a façade. It is a mask that must be ripped off. In seeking confirmation for this assumption, he entertains himself by putting people in impossible situations that will reveal their core corruption. He revels in pushing people who think they are good into embracing their inner evil. Hence his obsession with ripping off Batman’s mask. He must show the world that Batman is as bad as he is.

In pursuit of this confirmation, he is as clever as the devil. He has pressed the city government into evacuating people by means of two boats, one with prisoners and another with regular citizens. He gives a detonator device to the drivers of each ship. He says that he is performing a social experiment. The idea is that each detonator blows up the other ship. If you press the button to blow up the other ship, your ship will be saved. If you do not press quickly, your ship will likely be blown up because surely the people on the other ship will press first. So we have here the classic case of the prisoner’s dilemma without the mathematics. It is a raw test of the capacity of others to commit unspeakable crimes in their own self-interest.

At first, the social dynamic takes a predictable direction. Neither the citizens on their boat nor the prisoners on the other boat favor murder. But then they think again. What will the people on the other boat do? Surely the criminals on the prisoner boat will think nothing of pushing their button, so should the citizens act first? Meanwhile, the prisoners figure that the people on the other boat will not place much value on the lives of criminals, so they will probably be killed. Shouldn’t they kill first?

The debate becomes furious on each boat. On the citizen boat, for example, they decide to take a vote. The option of pushing the button wins (failure of democracy) but no one can find the will to do the deed. On the criminal boat, they just decide to explode the other boat, but the leader can’t quite do it. Finally, the clock moves toward the hour that the Joker said the experiment would end. Both sides have finally declined to do the dirty deed. In prisoner’s-dilemma terms, they have chosen cooperation over defection. This is not what the Joker expected. And why not? Because he doesn’t believe in the capacity of human beings for social cooperation. He assumes that everyone is like himself. And here he is wrong.

I’ve already mentioned that the mob figures into the plot here. In fact, it is the source of all crime, and the central driving force behind the entire plot. Every time a new person gains public office or position within the police department, he swears to clean up the streets of the mobster-driven crime problem. But each time, the person is either killed or corrupted, leaving it to Batman to do the dirty work.

But can Gotham ever really be cleaned up? At some point, a new district attorney has hundreds of people locked up and the assets of many local banks frozen. Even in this case, the mob money finds safe harbor outside the country. The more that the police try to enforce the law, the worse the crime problem grows and the more powerful the mob becomes. The film offers not the slightest hope that this issue can ever be resolved.

And yet there is a point that is never addressed in the film. Where does organized crime get its money? Bribes, no doubt. Probably business too. Is it gambling, prostitution, drugs, liquor, or something else? Whatever the case may be, the mob is the mob because it deals with black markets in something. The only reason that black markets exist is due to government prohibitions. A free market in gambling would reduce the level of corruption in this industry to the same level that it exists in the market for, for example, hamburgers. That is to say, it would not be a notable feature of the sector. The same is true with all traditional mafia activities. The best way — really the only way — to end its power is to end the prohibitions on peaceful trading of all goods and services.

But that is not what the state does. Instead, it fights these untenable and unwinnable wars against gambling, prostitution, drugs, and the like, and thereby drives them underground, guaranteeing high profits to those willing to take the risk to be part of the market. The riches are then used to bribe public officials and gain a certain amount of protection from the public sector. The cycle continues until the corruption becomes a deeply embedded part of public life. In this case, the prohibitions have unleashed wicked mobsters, but as bad as they are, they seem manageable.

The Joker, however, is not manageable. He is the killer virus unwittingly unleashed by the cure. People like him will always be with us, but they can usually be contained — unless the state is involved to make such people more powerful than they would otherwise be. The implied lesson becomes clear. The Joker is the product of mistaken public policy, the end result of the prohibition of peaceful trade.

The contrast between the peaceful cooperation that people are capable of when they are on their own, even under extreme circumstances, and the evil unleashed by misguided state management of society could not be more palpable.

This is the real message of Batman: The Dark Knight, which, I must say, is one of the most spectacular and profound cinematic explorations of the problem of evil I’ve ever seen. It is not suitable for young children, but I recommend it very highly, not only for its libertarian theoretical structure but also for its moral power.