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How to Remain Logical in an Argument

By Douglas Wilson
Printed in Practical Homeschooling #10, 1995.

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Douglas Wilson


In a world of over-inflated balloon arguments, logic supplies the student with an array of sharp, ready-to-use pins. The study of formal logic enables the clear-minded student to distinguish a valid argument from an invalid one. Obviously not an abstract exercise, like a class in theoretical mathematics, logic is one of the most practical subjects your children will ever study.

In everyday life, all of us must distinguish the plausible from the preposterous. More than ever, I find it hard to throw a rock without denting somebody’s fallacy.

Counter That Example!

One good way to illustrate the invalidity (or the true nature) of an argument is through counter-example. A successful counter-example presents the same basic form as the first argument, but because the nouns have been changed, the ludicrous nature of the first argument becomes immediately apparent. The statement that seemed plausible when it involved the balance of trade between Japan and the United States loses its force when applied to Montana and Idaho. And that makes me wonder, what exactly is the trade deficit between North and South Dakota?

Around the dinner table one evening, our family discussed the retroactive aspect of President Clinton’s tax program. My son commented, in an off-hand way, that Clinton’s program was like the pizza delivery boy showing up a week later after his delivery to inform us that they raised their prices, and we owe him money. This was a good counter-example.

Name That Fallacy!

The ability to name the fallacy presents another good defense against modern logical puffery. When people disagree, there is a common temptation to chalk this up as a simple matter of “opinion.” Now, sometimes disagreements are just a matter of opinion (for example, whether or not mushrooms taste like erasers). But frequently, disagreements are the result of one person being . . . well, wrong. Training in logic will keep your children from membership in that great, growing multitude which constantly says, “Right? Wrong? That’s your opinion!”

Affirming the Consequent. For example, a common logical error is that of “Affirming the Consequent.” In symbolic form, it looks like this: “If p, then q. Q is true. Therefore p.” “If I study hard, then I will get an A on the test. I got an A on the test. Therefore, I must have studied hard.” This is a fallacy. When a student has learned to identify this error in reasoning, he will soon have the unexpected pleasure of seeing it manifested everywhere. (This is something like buying a yellow Volkswagen. The next day you see them all over town and begin to suspect a massive practical joke.)

Suppose a politician says, “All great statesmen were maligned in office—just as I was maligned yesterday by Senator Snortworst.” It would be a great delight to have your teenager point at the flickering shadow universe of “World News Tonight” and shout, “Affirming the Consequent!”

Or suppose that, at church, your children hear some people talking about a “Christian” seminar they attended for people who were abused in childhood. The counseling guru said that one of the prime indicators of past abuse is the fact that the abused cannot remember it. One of those who attended says, “Why, I can’t remember a thing.” Your kids say to each other, on their way to the parking lot, “Affirming the Consequent”!

The central reason many modern Christians have the doctrinal discernment of a vacuum cleaner is that they have not been trained to think. If we are diligent and careful, we can avoid this problem with our children. We can teach them to think carefully and properly about everything they encounter.

The Either/Or Fallacy. Of course, there are many more fallacies than just “Affirming the Consequent.” Suppose your church is considering a wild and crazy youth ministry, and one of the arguments is: “We have to do something to prevent the kids from being lured to drinking parties.” This is bifurcation or, as it is sometimes called, ”the either/or fallacy.” Are these the only two choices—getting drunk on your town’s back roads or acting drunk at your church? Of course not!

Bulverism. Ever-popular is the fallacy of Bulverism, named by C.S. Lewis. It is the idea that an argument can be refuted if a plausible reason can be presented explaining why and how the person came to their decision. Truth and validity disappear as the all-important matter of motives take their place.

Suppose your children are telling someone that it isn’t right to be entertained by questionable movies and they run into the retort, “Oh, you are saying that because you’re homeschooled.” On the outside your children may politely say, “Ummm . . . ” but on the inside, if taught well, they will be saying, “Bulverism.”

Many more over-inflated balloons exist than those listed here. But, if your child is well-trained in logic, he will always have more than enough pins.

PUBLISHER’S NOTE: Sadly, this is Douglas Wilson’s last column with us. His increased duties with Canon Press, his various school commitments, and his editorship of Credenda/Agenda no longer leave him time to write for PHS. We shall miss him!

However, classical education will not be left without a voice in PHS. Starting next issue, Fritz Hinrichs of Escondido Tutorial Service, founder of the Great Books Tutorial, will be our classical columnist. Our sons have been taking Fritz’s tutorial, and I can tell you, he knows the classics!


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