Peter T. Leeson


On his book WTF?! An Economic Tour of the Weird

Cover Interview of February 25, 2018

A close-up

At each exhibit, you’ll learn about a different, seemingly insane ritual used to organize human life, and learn a different lesson about how to use economic logic to find its underlying sanity. Take, for instance, judicial ordeals: For more than 400 years, between the ninth and the early thirteenth centuries, European legal systems adjudged the guilt or innocence of criminal defendants by asking them to plunge their hands into a cauldron of boiling water to pluck out a ring. In these ordeals, a priest asked God to let the water burn the defendant’s hand if he were guilty and to perform a miracle that prevented the water from burning his hand if he were innocent. Confidence that God would fulfill the priest’s request reflected a popular belief according to which these ordeals were iudiciua Dei—“judgments of God.”

On the surface, these ordeals seem, well, stupid. But think about them for a moment using economic logic, in terms of incentives…

Suppose you’re a medieval European who’s been accused of stealing your neighbor’s cow. The court orders you to the ordeal. Like other medieval Europeans, you believe in iudicium Dei—that a priest, through the appropriate rituals, can get God to reveal the truth, performing a miracle that prevents the water from burning you if you’re innocent, letting you burn if you’re not.

If you undergo the ordeal and God says you’re guilty, you have to pay a large fine. If He says you’re innocent, you’re cleared of the charge and pay nothing. Alternatively, you can avoid undergoing the ordeal by confessing to having stolen the cow. If you confess, you pay a fine, but a smaller one since you came clean.

What will you do?

Suppose you’re guilty: You know you stole your neighbor’s cow, and so does God. In this case, you expect that if you undergo the ordeal, God will let the boiling water burn you, evidencing your guilt. Thus, you’ll have to pay the large fine, and you’ll have your hand boiled to rags, to boot. In contrast, if you confess, you’ll save a bit of money, not to mention your hand. So, if you’re guilty, you’ll confess.

Now suppose you’re innocent: You know you didn’t steal your neighbor’s cow and, again, so does God. In this case, you expect that if you undergo the ordeal, God will perform a miracle that prevents the boiling water from burning you, evidencing your innocence. Thus, you won’t have to pay any fine, and you’ll keep your hand intact. In contrast, if you confess, you’ll have to pay a fine for a theft you didn’t commit. So, if you’re innocent, you’ll undergo the ordeal.

Are you staring to see the logic? Because of your belief in iudicium Dei, the specter of the ordeal leads you to choose one way if you’re guilty—confess—and another way if you’re innocent—undergo the ordeal—revealing the truth about your criminal status though the choice you make. By asking God to “out” you, the legal system incentivizes you to “out” yourself!

I know what you’re thinking: “But the water will still boil everyone who sticks their hand in it!” And you’re right—if the water is actually boiling. But it wasn’t; to find out how and why, you’ll have to take the tour, where this and umpteen other questions that just occurred to you about these ordeals are answered.