Logical Fallacies

Notes

What is a Logical Fallacy?

• A fallacy is an error in reasoning. These are flawed statements that often sound true.

• What does it mean to reason with someone?

What is a Logical Fallacy?

• To reason with someone is to try to persuade someone to do something by explaining why you think it is sensible.

• So, to reason with someone is to try and understand their point of view, to know where they are coming from and to let them know that you are open to acknowledging how they feel so that you can come to an agreement or understanding.

What is a Logical Fallacy?

• Logical fallacies are often used to strengthen an argument, but if the reader detects them, the argument can backfire and damage the writer’s credibility.

Origins• The word ‘fallacy’ may have been derived

from the Latin word ‘fallere,’ meaning “to deceive, to trip or to lead into error.

• OR, it may have been derived from the Greek ‘phelos,’ meaning “deceitful.”

• http://www.youtube.com/watch?v=VL9whwwTK6I

Why study logical fallacies?• It is important to develop logical fallacy

detection skills in your own writing, as well others

• Think of this as an “intellectual kung-fu: the art of intellectual self defense”!

• OR…consider it your Bull S--- Radar!

• Okay, now don’t tell your mother Mrs. Cable used a bad word!

Types of Logical Fallacies

Ad Hominem Argument

• Name-Calling, smearing the person instead of attacking the argument.

• Ad hominem is an attempt to persuade someone of the value of a premise based on the characteristics of the person holding that premise. It can be either positive or negative, and both are logical fallacies.

• Negative: "You can't believe Jack when he says the proposed policy would help the economy. He doesn't even have a job."

• Because Jack doesn't have a job, he shouldn't be expected to know anything about the economy.

Ad Hominem Example• Positive: "That man was smartly-dressed and

charming, so I'll accept his argument that I should vote for him." or: "He must be the best candidate; after all, he's a Christian!"

• Because he dresses nicely, or has a particular religion, he must know a lot about politics, economics, and statesmanship. https://www.youtube.com/watch?v=4oLYqUT24Vk

•

The ultimate ad hominem is to simply insult the person outright: "You can't believe anything in this book because the author is an idiot!" (i.e., I disagree with everything in the book, but don't know enough to formulate reasons why, so I'll just insult the author).

Or My Favorite

• Any time a woman stands up for herself she risks hearing…

• “Are you PMS-ing?”

Simply Stated…

• Person A makes claim X.

• Person B makes an attack on person A.

• Therefore A's claim is false.

Begging the Question• Falsely arguing that something is true by

repeating the same statement in different words.

• Arguing off the point; changing direction.

• Evades the question.

• No real logical evidence has been given.

Begging the Question Example• Interviewer: "Your resume looks impressive

but I need another reference." Bill: "Jill can give me a good reference." Interviewer: "Good. But how do I know that Jill is trustworthy?" Bill: "Certainly. I can vouch for her."

• Often referred to as “Circular Reasoning.”

Simply Stated…

• Begging the question similarly takes the form:

• A implies B and A is only valid because B is assumed.

False Analogy• An analogy that does not stand up to logic.

• Many arguments rely on an analogy between two or more objects, ideas, or situations. If the two things that are being compared aren’t really alike in relevant respects the analogy is weak.

• Employees are like nails. Just as nails must be hit in the head in order to make them work, so must employees.

False Analogy

• a·nal·o·gy• əˈnaləjē/• noun• a comparison between two things,

typically on the basis of their structure and for the purpose of explanation or clarification.

Another False Analogy…• Guns are like hammers. They’re both tools with

metal parts that could be used to kill someone, and yet it would be ridiculous to restrict the purchase of hammers, so restrictions on purchasing guns are equally ridiculous.

• How is this analogy false?

False Analogy Explained• While guns and hammers do share certain

features, these features (having metal parts, being tools, and being potentially useful for violence) are not the ones at stake in deciding whether to restrict guns. Rather, we restrict guns because they can easily be used to kill large numbers of people at a distance. This is a feature hammers to not share – it’d be hard to kill a crowd with a hammer (but please do not try this at home). Thus, this is a weak analogy!

Simply Stated• A and B are similar;

• A has property P, so the argument is that B also has property P;

• The analogy fails if A and B are different in a way which affects whether they both have property P.

Either – or Reasoning

• Presenting only two options when it is possible to have more.

• Example: President George W. Bush: “You're either with us or against us.”

Either-or Explained

• These types of arguments fail because the audience is not given a fair choice – there exist many alternate (and often more desirable) choices that are never offered to the listener for consideration.  Isn’t Switzerland a neutral country?  (Yes.)  So, are they “for” or “against” the United States?  Do you love every part of your best friend’s personality?  Does that mean that you too are “for” or “against” this person?

Simply Stated…

• Either claim X is true or claim Y is true (when X and Y could both be false).

• Claim Y is false.

• Therefore claim X must be true.

Hasty Generalization

• Reasoning based on insufficient evidence.

• This fallacy is committed when a person draws a conclusion about a population based on a sample that is not large enough.

• Small samples will tend to be unrepresentative.

Hasty Generalization ExampleBill: "You know, those feminists all hate men."

Joe: "Really?"

Bill: "Yeah. I was in my philosophy class the other day and that Rachel chick gave a presentation."

Joe: "Which Rachel?"

Bill: "You know her. She's the one that runs that feminist group over at the Women's Center. She said that men are all sexist pigs. I asked her why she believed this and she said that her last few boyfriends were real sexist pigs. "

Joe: "That doesn't sound like a good reason to believe that all of us are pigs."

Bill: "That was what I said."

Joe: "What did she say?"

Bill: "She said that she had seen enough of men to know we are all pigs. She obviously hates all men."

Joe: "So you think all feminists are like her?"

Bill: "Sure. They all hate men."

Simply Stated…

• Sample S, which is too small, is taken from population P.

• Conclusion C is drawn about Population P based on S.

Post Hoc Reasoning• Assuming that because two things happened, the

first one caused the second one.

• Sequence is not causation.

• I had been doing pretty poorly this season. Then my girlfriend gave me this neon laces for my spikes and I won my next three races. Those laces must be good luck...if I keep on wearing them I can't help but win!

Simply Stated…

• A occurs before B. • Therefore A is the cause of B.

• "The Urban Institute, a research organization based in Washington, has released an interesting report that suggests that the proliferation of iPods helps account for the nationwide rise in violent crime in 2005 and 2006.

The report suggests that 'the rise in violent offending and the explosion in the sales of iPods and other portable media devices is more than coincidental,' and asks, rather provocatively, 'Is There an iCrime Wave?‘”

Let’s Practice!http://www.youtube.com/watch?v=d29VsG35DQM