The Web's Most Illogical Arguments

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The Internet is teeming with crazies, jerks, and blowhards; and in online forums, debaters are full of passionate intensity. Peruse the comments area on any popular blog, and you'll find more irrational rhetoric than you can shake an encyclopedia at.

What separates rational thought from bogus blather is logic. Unfortunately, sound logical thinking is a learned skill that's rarer than we might hope, and it's not the same as so-called common sense.

Many irrational comments are so clearly false that anyone can identify their shortcomings, but other fallacies may appear sensible at first glance. To help you separate the rational from the just plain wrong, I've rounded up examples of the most common logical fallacies you'll encounter on tech forums. I'll explain why these arguments don't work, so you'll be better equipped to counter them when someone uses them against you.

What's a Fallacy?

A fallacy is a logical error. Logic is a method of reasoning in which the statements used to support a conclusion must be true in order for the conclusion to be true. When the statements used to support a given conclusion do not actually work together to support the conclusion, we call this a fallacy.

It's worth bearing in mind that a statement can be fallacious even if its conclusion happens to be true. What differentiates sound reasoning from a fallacious argument is not the accuracy or inaccuracy of the conclusion it reaches, but its fidelity or infidelity to the principles of logic.

Using or falling for fallacious reasoning is by no means a sign of stupidity. Lots of smart people inadvertently use or get taken in by irrational arguments from time to time--through lack of attention, lack of understanding about how logic works, or the simple fact that human psychology is riddled with weird idiosyncrasies that make us susceptible to misunderstanding. And of course, some people deliberately use fallacious arguments because they know that others will fall for them.

Here are ten of the most common logical fallacies that you'll find online.

Bald Assertion

The iPod is the best music player on the market.

Oh, really? Prove it.

PC World's forums are chock-full of bald assertions like the one above. What makes this kind of statement fallacious is the sheer absence of evidence offered to support it. Many online commenters don't bother to back up their claims with facts, and this makes assessing the reasonableness of their assertions difficult. That being the case, it's hard to fault someone for dismissing such a statement out of hand--even if it's true.

Think Opera is the best browser around? Okay, fine. But unless you can explain why you think so, you offer readers very little reason to care about or come around to your opinion.

A good rule of thumb for avoiding this problem in your own online posts is to consider how controversial your statement is likely to be. If you suspect that reasonable people might need a little convincing, it's best to offer additional reasoning and to refer to supporting evidence.

Ad Hominem

You obviously don't know anything about Windows, because you're a Mac fanboy.

Don't feel like making an honest case to refute a statement you don't like? Why not just attack the person directly? When you target the person you're arguing against instead of focusing on the content of their argument, that's called an ad hominem fallacy. "Ad hominem" literally means "to the person," and it's one of the most blatant fallacies you'll find anywhere.

Rather than address the actual reasons why someone may be wrong, the ad hominem arguer takes the lazy way out and attacks some irrelevant facet of the opponent's personality or background. In reality, whether someone is a fanboy or not doesn't automatically validate or invalidate what they say. Even a Mac fanboy can make true statements about Windows.

Another common form of ad hominem argument--and one commonly used against tech journalists--goes something along the lines of "You can't trust anything this guy says, because he's been paid off by Microsoft/Apple." Unsurprisingly, whenever we say something critical of one company, we're accused of taking bribes from the other.

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