By Randall Smith.

"Oh, so you're using logic," said the young man when I pointed out he had contradicted himself. "I'm not confined by logic." And Lord knows, he hadn't been. That was one thing we could agree on.

If your math teacher asks, "What is 2 + 2?" and you answer "10," and she says, "No, that's not right," it won't help to say, "Oh, so you're using mathematical logic? I don't wish to be confined by that."

Whatever "philosophy" you may have studied, two dollars plus two dollars does not equal ten dollars. And statements can't be both true and false at the same time in the same respect. These aren't just made-up "rules" that you can bypass like the rule against chewing gum in school. They are expressions of reality.

What's at stake here isn't merely an abstract "academic" debate about "logic." The tragic result of rejecting logic is that it insulates you from taking seriously any meaningful critique of your views. One can always take refuge in the claim, "Oh, that's just logic." But that's like saying: "Oh, so you think statements should make sense?" Well, yes, actually, I do. And quite frankly, so does everyone else!

Now, to be fair, this isn't the only way people insulate themselves from meaningful critique. An even more common way is to commit a logical fallacy, mistaking it for a real argument.

There is, for example, the Fallacy of Relevance: citing evidence or arguments that are irrelevant to the conclusion they are supposed to support. During the Second World War, the commander of German Reserve Police Battalion 101 told his men, as he was giving them the order to slaughter 1500 Jewish women and children in a small Polish village, that they should "remember that Germans were being killed by bombs back in Germany."

Yes, but these Jewish women and children had nothing to do with those bombs, and murdering them would do nothing to make the bombing stop. It may sound like an argument, but it's not. People cite evidence and arguments all the time that have precious little relevance to the dramatic conclusions they wish people to embrace.

And then there is the famous Ad Hominem Fallacy: thinking that an attack on the person is enough to refute his argument. Politician X may be a lying shyster, but that doesn't make his argument wrong. If we could convince people that ad hominem arguments are empty and invalid, most of what passes for political discourse would simply vanish. Even if Republicans are "greedy," and even if Democrats are "hypocrites," that tells us nothing about their specific arguments about taxes and the budget - unless their only arguments are that Republicans are greedy, and Democrats are hypocrites.

Then there are Fallacies of Ambiguity: arguments that rely on vague or ambiguous language. What does it mean to say, "We should tax the rich"? Maybe we should, but who is included in the category "rich"? Who are "the poor" and how will taxing "the rich" help them? It might, but we would need to know how, and then we would need to verify whether it is actually helping.

Straw Man arguments are also common. This is when people misrepresent the arguments of the other side to make them easier to attack. It's usually done by re-stating the argument without the supporting evidence or by using different, more emotionally laden terms. "They're trying to destroy the country!" Really? That would be an odd motivation for anyone living in this country.

Then there are slogans, repeated like mantras until they become nearly impossible to dislodge from the mind. "If men got pregnant, abortion would be sacred." Well, if women were white and living in the South in 1850, slavery would be sacred. Either way, slavery is wrong, and if men got pregnant, it would still be wrong to kill a living human being.

Many of these fallacies serve the partisan tribalism that currently bedevils our political discourse. People blind themselves to the illogic of their arguments because they take themselves to be supporting "the good guys." Th...