17 Sep 2007

I often get distracted when following discussions online due to the abundance of flawed logic. It's distracting enough that I sometimes find myself tending to disagree with someone whose argument is illogical, even if I agree with the conclusion. (I can usually overlook poor grammar, as long as it's not too bad; we all make mistakes.) The following logical fallacies are the ones that I notice most often:

In case you're a pedant, note that logical fallacy is "often used more generally in informal discourse to mean an argument which is problematic for any reason, and thus encompasses informal fallacies as well as formal fallacies." Hopefully you can tolerate such informal discourse. :-)

Affirming the Consequent is something I first remember hearing about in high school, when a math class took a brief foray into logic. I can still remember the example, because it made the fallacy quite obvious:

  1. If A is a dog, then A is an animal.

  2. A is an animal.

  3. Therefore, A is a dog.

This was contrasted with a logical conclusion:

  1. If A is a dog, then A is an animal.

  2. A is not an animal.

  3. Therefore, A is not a dog.

A good example can be found in an old post of mine, Top X List of Mac OS X Annoyances. Although I don't mention Windows and only focus on my experience with Mac OS X and Linux, many people commented under the assumption that I use Windows. Now, I can't be absolutely sure how people came to this false conclusion, but I can speculate that their logic went something like this:

  1. Those who use Windows find some characteristics about Mac OS X annoying, but only because those characteristics are different.

  2. Chris finds some characteristics about Mac OS X annoying.

  3. Therefore, Chris uses Windows. (A related conclusion is that my opinion isn't valid, because I use Windows.)

Next on the list is the Ad Hominem Argument, likely the most popular online fallacy. If you've ever witnessed someone resorting to personal attacks, you know what I'm talking about. I always attribute personal attacks to the lack of a valid, logical argument. (I'm almost always right about this, too.) The false premise upon which this fallacy is based is that by attacking someone who holds a certain position, you attack the position itself.

Last on the list is my personal pet peeve, the Straw Man Argument. This is often described as putting words in someone's mouth, but more specifically, it's when you misrepresent someone else's position in order to make it seem as if your position is superior.

What bothers me about the Straw Man Argument is that it is both very dishonest and very effective. This is a rampant problem in politics, at least here in the US. We often hear:

My opponent would have you believe...

In most cases, whatever follows is not at all what the opponent wants you to believe. Lies are nothing new in politics, but this particular variety is extremely effective. (The Straw Man Argument is very popular on FOX News.)

Got any more to add to the list?

If you want to learn more, logicalfallacies.info looks like a good resource.