There are two great difficulties confronting any journalist who proposes to write a column on logic. The first is how to avoid sounding pretentious, and the second is how to avoid boring the reader to tears. As for the first difficulty, that of not sounding pretentious, I may say right off that I am an imbecile, a dolt and a moron, and so nip any affectation of arrogance or pretense right in the bud; and as for the second, that of keeping the reader (you) interested, I will stay away from all the boring theory, and work only in examples. So let us begin.

Suppose John and Mary are arguing, and Mary says, “We should not have attacked Iraq because there was no evidence that the Iraqis were involved in Sept. 11.”

Is Mary’s argument valid?

No, it is not. Mary is assuming that all possible justifications for attacking Iraq must have involved Sept. 11. There are many other possible justifications: that the Iraqis possessed weapons of mass destruction, that the Iraqis have a lot of oil, etc.

Now consider John’s objection to Mary’s argument:

John: “You’re fat.”

Is John’s objection a valid one?

No. Mary may be fat, or foolish or even insane; but these traits to do not affect the legitimacy of her argument. The truth of an argument has nothing whatsoever to do with the person stating it, and attacking that person says nothing about whether the argument is valid. (A lot of my critics would do well to recognize this.)

Another little argument, this time involving Jack and Jill:

Jack: “We shouldn’t allow people to burn the flag because we shouldn’t burn the sacred symbol of our country.”

Is Jack’s argument valid?

No, it is not. The second part of Jack’s argument is just a restatement of the first. He might as well be saying “We shouldn’t burn the flag because we shouldn’t burn the flag.”

Now, Jill’s response:

Jill: “Well, my uncle served in Vietnam, and he burned an American flag in protest, so it’s all right.”

Jill’s response is no more reasonable than Jack’s. The fact that her uncle burned a flag, or drinks a handle of vodka a day or has 19 heads has nothing whatsoever to do with whether it is right to burn a flag. The question of whether the flag should be burned is independent of whether any person actually does it.

Now consider Jack’s counterattack:

Jack: “Well if you think we should be able to burn the flag, you can just get the hell out of the country, and move to France!”

Jack is, of course, right; Jill can indeed leave the country and go live in France. But the fact that Jill can go live in France does not prove that it’s wrong to burn the flag.

Another little argument, involving Frank and Vanessa (I always liked the name Vanessa):

Frank: “You shouldn’t smoke marijuana, because students who smoke marijuana have lower GPAs, on average, than students who don’t.”

Is Frank’s argument valid? No, it is not. Just because many students who smoke marijuana have lower GPAs does not mean that smoking marijuana causes bad grades. It might very well be that students who do not study have nothing to do, and so they smoke pot all day, to pass the time.

Now consider Vanessa’s response: “Marijuana doesn’t cause anyone to get bad grades. I’m high right now, and I have a 4.0.”

Vanessa, too, is mistaken. Just because she can smoke pot and get good grades, does not mean this is true for anyone else. A generalization based on a single instance is invalid.

Let us consider one final example. Suppose Ludwig and Helga are talking, and Ludwig says, “Hey, Helga, our test is tomorrow, so you’d better study if you want to do well.” Is it logically valid, then, for Helga to go and study her cute little Nordic butt off for the next five hours?

No, it is not. And do you know why? Ludwig was lying. The test is not for two weeks; Ludwig was just enjoying a joke at Helga’s expense. Logic is a powerful tool, but it only works when it is applied to true premises.

Gullibility is the crudest of all logical errors. Fortunately it’s also the easiest to spot. It’s standing right in front of you.

E-mail Jeff at [email protected].