1. Avoiding Logical Errors
Common Places: Integrated Reading and Writing
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2. Logical errors are also known as fallacies
Logical errors are also known as fallacies. Five common logical fallacies are:
Slippery Slope
False Dilemma
Hasty Generalization
Straw Man
Weak Analogy
Logical Errors

3. The Slippery Slope Fallacy
This fallacy asserts that if you take a few steps down the slope, you’ll fall to the bottom (and die!) A slippery slope is a prediction that is not supported with enough evidence. Its purpose is to make people fearful to take an action.
The Slippery Slope Fallacy

4. Example of a Slippery Slope
Jennifer: If we legalize marijuana for recreational use, the next thing you know, ecstacy, crack cocaine, and heroin will be legal, too. Do you want your kids thinking those drugs are okay to use?
What’s the problem?
Jennifer’s prediction that these other more dangerous drugs will also be legalized is not based on evidence. Rather, she hopes to make people fearful by convincing them that x (legalizing marijuana) will lead to y, something disastrous (legalizing much more dangerous drugs.)
Example of a Slippery Slope

5. The False Dilemma Fallacy
A dilemma is a choice between two options. A false dilemma asserts that there are only two options when, in fact, more options are available.
We can either stop illegal immigration or open the gates for everyone to come into the US.

6. Example of a False Dilemma
A bumper sticker says:
America: Love it or Leave It!
What’s the problem?
In the 1970s, this bumper sticker slogan was popular. The idea was directed at citizens who criticized the US government for its involvement in Vietnam. The slogan suggests that you have only two choices: “love” America by not criticizing the government’s decisions, or leave America. There are, however, more choices that those two! People who love America can also criticize it.
Example of a False Dilemma

7. The Hasty Generalization Fallacy
“Tim lives in Texas. I wonder how many horses he has?” Do all Texans have horses? Some Texans do, but it is illogical to think that some means most or all. A hasty generalization makes an assumption based on a small bit of data.
The Hasty Generalization Fallacy

8. Example of a Hasty Generalization
Michael: I bought a new, 2015 Lexus sedan, and it has been in the shop for the last two months. Now the transmission has to be replaced! 2015 Lexus sedans are mechanical failures!
What’s the problem?
Michael has had experience with only one 2015 Lexus sedan: his own. What if every other 2015 Lexus sedan was mechanically flawless? Michael does not have a large enough sample of 2015 Lexus sedans to make the assertion that they are mechanical failures. He has made a hasty generalization.
Example of a Hasty Generalization

9. Have you ever gotten into a fight with a scarecrow
Have you ever gotten into a fight with a scarecrow? You’ll win every time! A straw man argument occurs when you make the opposing argument seem so ridiculous that you can easily overturn it.
The Straw Man Fallacy

10. Mayor: We won’t be offering the free senior adult health screening day this year because we lack the funding. The cost of replacing the bridge on 16th Street will be twice what we budgeted.
Pat: The city isn’t offering the free senior adult health screening day because, like the rest of society, this city doesn’t care about elderly people.
What’s the problem?
Pat is not addressing the mayor’s real reason: the fact that the bridge replacement costs more than was planned and is considered more important than the screening day. Rather, by creating a bogus reason for the city’s decision (that the city doesn’t care about elderly people), Pat believes she can more easily win the argument. This is unfair.
Example of a Strawman

11. The Weak Analogy Fallacy
Marijuana and alcohol: when is it fair to compare the two? Analogies compare two unlike things and point out the ways in which they are similar. Weak analogies fail to acknowledge important differences between the two things become compared.
The Weak Analogy Fallacy

12. Example of a Weak Analogy
Rita: In the same way that I’m a customer when I spend money at a grocery store, I am a customer when I pay my tuition for college. And when I pay for groceries, I expect to leave with groceries. So when I pay for college, I expect to receive good grades.
What’s the problem?
Rita is correct that college and groceries are both goods that require payment. She is wrong, however, about the goods she is paying for. In the case of groceries, she is paying for a product. In the case of tuition, she is paying for an opportunity. This is a weak analogy.
Example of a Weak Analogy

13. The End