Everyone from Paul Martin to Dalton McGuinty and Jack Layton agrees that tough sentences are part of the solution to gun crime. They're all wrong. But no one is more wrong than Stephen Harper, whose long list of bare-knuckle justice policies would completely transform the criminal justice system. For Mr. Harper, punishment is the solution to gangs. And drugs. And child abuse. And pretty much every other form of undesirable behaviour. Far more than any other politician -- even other conservative politicians -- he will use punishment as a social policy tool. I think there's a very specific reason for this. It's not that Stephen Harper has a fetish for uniforms and prisons. It's that he has a master's degree in economics. In classical economic theory, human beings are rational. We take in information and make calculations based on it. And our calculations are always based on the simple principle that we "maximize utility" -- meaning we avoid the bad stuff whenever possible while piling up as much of the good stuff as we can get our hands on. Our species is "homo economicus" -- economic man. It's a neat, clean, simple theory. And it leads to neat, clean, simple conclusions about all sorts of human behaviour -- including crime. Say you're a criminal and you're thinking about robbing a corner store. If you do it, you'll get a bunch of money. But there's also a chance you will be caught and punished. Should you do it? For the classical economist, your decision will depend on a simple calculation. If the money outweighs the risk of getting caught and punished, you will commit the robbery. If it doesn't, you won't. That leads to an obvious conclusion about how to fight crime: Increase the risk. That will tilt the calculation against committing the crime. You will be deterred. So how do we increase the risk to would-be criminals? There are two ways. First, we can boost the chance of getting caught. Unfortunately, that's difficult. In some circumstances, it may be impossible. The other way to increase risk is to boost the punishment. That's very easy to do. We only have to pass a law. This is why Mr. Harper wants to pass a long list of laws that would drastically increase sentences. He knows the theory. In the leaders' debate, he said his crime policies would produce "deterrent effects." That's an economist talking. Or, to be more precise, that's an old-fashioned economist talking -- because only old-fashioned economists still believe in the myth of "homo economicus." For many decades, psychologists and other researchers have been exploring how human brains really work. What they discovered is that human beings -- big surprise -- are not walking calculators. There are two basic systems of human thought. One is reasoning. It involves slow, conscious, careful thought. This sort of thinking fits with the old economic theory. The second system is very different. It is intuition -- instinct, emotion, gut feeling, reaction and snap judgments. This track can be very useful, even vital to survival (you don't have time to calmly ponder the variables when a scowling man walks toward you with clenched fists). But it is irrational. It is filled with quirks and flaws. Sometimes the thoughts it produces are downright nutty. The problem for the old economic theory is that a whole lot of people's thinking is done with the intuitive system. Researchers have found that even in the sober environment of university laboratories, people lean heavily toward intuition. "People are not accustomed to thinking hard," said Daniel Kahneman, the leading scientist in the field, "and are often content to trust a plausible judgment that comes quickly to mind." That quotation comes from a speech Mr. Kahneman gave accepting the 2002 Nobel memorial prize in economics. It was the second Nobel awarded to researchers whose work undermined the old economic theory. The first was to Herbert Simon in 1978. In fact, Mr. Kahneman's Nobel was proof that the long debate is coming to a close: Like Santa Claus, homo economicus does not exist. Most economists now accept this. There's even a branch of economics dedicated to bringing psychology into the dismal science. But still there are holdouts, economists who love the old, simple theory and refuse to give it up. They can be found in the dustier economics faculties. Others are policy wonks in neo-conservative think-tanks. Some are politicians. I admit all this may sound obscure. It's not. It bears directly on the question of how we should fight crime. Criminologists have examined deterrence in countless studies and they have reached a rough consensus. It turns out that criminals can be deterred by increasing the risk of getting caught. But they cannot be deterred by making punishments tougher. For psychologists, this conclusion doesn't present any difficulties. It's just another example of human irrationality, another quirk of the human brain. But for economists clinging to the idea of homo economicus, what the criminologists have found is impossible. It doesn't fit the theory. So how do old-fashioned economists deal with what the criminologists' research? They pretty much ignore it. And that is how we got to Stephen Harper's get-tough justice policies. They will cost billions of dollars. And criminologists agree they won't deter crime. But still Mr. Harper is pressing ahead with them, confident that tougher sentences will make our communities safer. Because that is what an old, discredited theory says.