As campaign controversies go, it was minor stuff: Ottawa mayor Larry O'Brien accused the government of Ontario of funding a study to examine the feasibility of safe-injection sites in the province -- and of keeping the study under wraps until the Oct. 25 municipal elections were over. This was immediately denied. The province hadn't funded the study. And the study hadn't been released because it hadn't been completed. O'Brien withdrew his accusation and the media mused about the damage this embarrassing performance would do to his campaign. And that was the last we heard of it. Which is unfortunate. Because this little incident was only trivial in a political sense. Seen from the perspective of how public policy is made, it is devastatingly revealing. Go back to O'Brien's original press release. "The fact that this research is even considering drug injection sites for Ottawa," it said, "should be of concern to every resident." O'Brien wanted to make an issue of the study because he is adamantly opposed to the creation of an injection site. And he thought he could score votes with his opposition. It didn't work out that way, however. Jim Watson, his main opponent, said he is also opposed to the creation of a safe-injection site. For good measure, police chief Vern White called safe-injection sites "absolutely ridiculous" and regretted that O'Brien had even mentioned the study. "I'm a little disappointed that we're giving this any legs," White told a reporter. So the issue was a political dud. But notice that not one of these civic leaders expressed the slightest interest in reading the study. No, their minds were closed. They already knew the truth. No need to examine evidence as it becomes available, and certainly no need to adjust opinions accordingly. This is indefensible. It is nakedly irrational. Unfortunately, it is also perfectly natural. Every brain is stuffed with certain understandings of human nature and how the world works. Some are the product of evolutionary hardwiring. Others come from personal experience and culture. Whatever their origins, they shape our subsequent perceptions and thoughts, thanks to the brain's insistence on maintaining order in its mental universe. When we encounter new information that fits with our existing beliefs, we have a natural tendency to embrace it uncritically. It's consonant. It fits. It sits comfortably in our brains and makes us feel good. But information that contradicts existing beliefs is dissonant. It's jarring, upsetting. And so we struggle mightily to find some excuse to reject it. Or ignore it altogether. The potency of this "confirmation bias" should not be underestimated. Brain scans actually show consonant and dissonant information is processed in different regions. That's how deep the bias runs. In a sense, the whole point of science, or any rational inquiry, is to overcome this crippling tendency to make facts fit beliefs. Don't cherry-pick evidence. Make an extra effort to find contrary evidence. And most importantly, be prepared to review evidence as it becomes available and change existing beliefs if the evidence suggests they are wrong. Unfortunately, the formal rules and informal cultural norms that keep science from veering off into confirmation bias are almost completely non-existent in democratic politics. "When the facts change, I change my mind," John Maynard Keynes famously said. "What do you do, sir?" For most politicians, the answer is: "I avoid facts that don't fit what I believe. Problem solved." Look at the Conservative government's mandatory minimum sentences, which the government says will deter crime. That's not an unreasonable hypothesis. Any evidence? In a 2006 interview, the justice minister claimed there were lots of studies that said so. So I called his office and asked for them. They gave me five citations. Four were old and used dubious methodologies; three of those four provided only very weak support for the government's claim, while the fourth actually contradicted the government's position. The fifth study was the most recent and the best quality. And it concluded mandatory minimums don't work. But more importantly, the Conservatives ignored a long list of other studies that contradicted their position. In other words, they cherry-picked. Badly. Since that time, the government has given up on evidence altogether. It simply makes assertions about the value of mandatory minimums and scoffs whenever criminologists say they're wrong. How is that even remotely rational? In politics, this sort of thing is so common we seldom stop to think how utterly bizarre it is. The recent ruling on the constitutionality of the prostitution laws is a perfect case in point. The trial judge spent months reading studies and listening to the testimony of both sides' experts. Much of the 132-page ruling is composed of a painstaking summary and evaluation of the voluminous evidence before the court. It's an invaluable resource. All the arguments and evidence in one document! So how many of the politicians who loudly objected to the court's ruling -- including the inimitable Larry O'Brien -- read the decision before spouting off? Judging by the many comments which were belied by evidence in the decision, I suspect none did. Imagine a scientist angrily rejecting the results of another scientist's study without bothering to even read the study. That would be outrageous, wouldn't it? Shocking. Irrational. And yet something similar happens all the time in politics. Of course it's easy to blame this on the likes of Larry O'Brien. But ultimately, it's not his fault. The media seldom ask about evidence. And the people don't insist that they do. Thus, in our political system, public policy is made by closed-minded politicians who play to the prejudices of an electorate in which knowledge and certainty tend to be inversely correlated. This system is called "democracy."