Sunday, March 1, 2015

Logical Fallacies

By: Hanna Mangold

At this point in your college career, you may have heard professors talking about, and discouraging, the use of logical fallacies in argumentative papers. The term “logical fallacies” actually refers to a wide range of errors in reasoning, and it can get a little confusing. I’m going to point out several definitions and examples in order to help you make sense of the logical fallacies problem.
Although the various types of logical breakdowns have specific names (you may have heard of the “Slippery Slope” or “Straw Man” fallacies), it’s much more important to recognize that a logical fallacy has been made, than to be able to identify the specific type of fallacy.

Once you become familiar with the logical fallacy concept, I’m sure you’ll start seeing them everywhere! Politicians and advertisers are infamous abusers of logic—usually as an attempt to discredit their competition. The problem, of course, is that an invalid argument ends up making them sound desperate and deliberatively deceitful. Sometimes logical fallacies are used for humorous purposes—these examples poke fun at people who use false logic.

Have you seen Monty Python and the Holy Grail? In one famous scene, a mob of medieval peasants seeks to convict a woman of witch craft (watch here: The mob’s logic (inductive and deductive reasoning) makes sense, but it is rendered completely fallacious by the false premises they set as indicators of witchcraft.
A more recent example can be found here (, in a compilation of DirectTV commercials. In this advertising campaign, DirectTV makes fun of advertisers who use faulty logic to promote their products, by using faulty logic in a humorous way.

So, onto the nitty gritty:

What is a logical fallacy?

1.     According to
The term "logical fallacy" refers to the concept of making an error in terms of reasoning. It is crucial to understand logical fallacies so that they can be identified and avoided when attempting to persuade.

2.     According to sources compiled on
An error in reasoning that renders an argument invalid.
“Logical fallacies are unsubstantiated assertions that are often delivered with a conviction that makes them sound as though they are proven facts" (McMullin, The New Handbook of Cognitive Therapy Techniques, 2000).
“A logical fallacy is a false statement that weakens an argument by distorting an issue, drawing false conclusions, misusing evidence, or misusing language" (Dave Kemper et al., Fusion: Integrated Reading and Writing. Cengage, 2015).

3.     According to the PurdueOWL:
 Fallacies are common errors in reasoning that will undermine the logic of your argument. Fallacies can be either illegitimate arguments or irrelevant points, and are often identified because they lack evidence that supports their claim. Avoid these common fallacies in your own arguments and watch for them in the arguments of others. (PurdueOWL)

Why is it important to recognize these lapses in reasoning?

·       In order to identify weak arguments in source material/news articles.
·       In order to think critically about what we hear and how people are attempting to persuade us.
·       In order to avoid making weak arguments in our own writing.

"There are three good reasons to avoid logical fallacies in your writing. First, logical fallacies are wrong and, simply put, dishonest if you use them knowingly. Second, they take away from the strength of your argument. Finally, the use of logical fallacies can make your readers feel that you do not consider them to be very intelligent" (William R. Smalzer, Write to Be Read: Reading, Reflection, and Writing, 2nd ed. Cambridge Univ. Press, 2005) (from

Think about it, why would you want to avoid making a logical fallacy? What does it do to your argument? To your authority on the subject?

The following links are a few great sources for exploring logical fallacies more closely: (some good definitions and examples) (a fun interactive website and printable poster that break down types of fallacies) (good definition and breakdown of examples by type)

For fun and practice, try figuring out what’s wrong with the following statements pulled from

Ladies and gentlemen of the jury, look at the bloody clothes, the murder weapon. Imagine the helpless screams of the victim. Such a crime deserves no verdict except guilty, guilty!

I’m not a doctor, but I play a doctor on TV, and I wouldn’t dream of using anything but Tylenol for my toughest headaches.

We should pass a constitutional amendment making it illegal to burn the American flag. Anyone who thinks otherwise just hates America.

Do most Americans believe in God? To find out, we asked over 10,000 scientists at colleges and universities throughout America. Less than 40 percent said they believed in God. The conclusion is obvious: Most Americans no longer believe in God.

The Soviet Union collapsed after taking up atheism. Therefore, we must avoid atheism for the same reasons.

You’re a vegetarian? You do realize that Hitler was a vegetarian, too?

The war in Iraq has been a complete success. After all, Saddam Hussein is dead, and the Iraqis had their first free election in years.

Most heroin users started out smoking pot. If you start smoking pot, you’ll end up a heroin user, too.

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