What is a logical fallacy?

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

• 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 derive from the Latin word fallere meaning, “to deceive, to trip, to lead into error or to trick.” The word may also derive from the Greek phelos, meaning “deceitful.”

www.sun-design.com/talitha/fallacies.htm

Why study logical fallacies?• It is important to develop logical fallacy detection skills in your own writing, as well as others’.

Think of this as “intellectual kung-fu: the art of intellectual self defense.” (Logical Fallacies Handlist)

Draw TableFallacy Definition Your Own Example

Ad Hominem – “to the man”

Ad Hominem

• A person’s character is attacked instead of his argument.– Senator Jones was a conscientious objector during

the Vietnam War, so his proposal to limit military spending has no merit.

– Why are you talking about an open campus? You cannot even drive, silly sophomore!

Ad populum – “to the crowd”

Ad Populum

• A misconception that a widespread occurrence of something is assumed to make it right or wrong.

Either/or or False Dilemma Fallacy

Either/Or

• Tendency to see an issue as having only two sides

Faulty Analogy

• Making a misleading comparison between logically unconnected ideas. The assumption that because two things are alike in some respects, they are alike in others.

– If we put humans on the moon, we should be able to find a cure for the common cold!

– IF teachers can use the phones and drink coffee in school, students should be able to also!

– If adults can legally drink alcohol, teenagers should be able to also!

Post Hoc Ergo Propter Hoc“after this, therefore because of this”

• Assuming that an incident that precedes another is the cause of the second incident.

• Every time I wear my blue sweater, it snows. OMG, MY BLUE SWEATER CAUSES SNOW!!!

Red Herring• An argument that focuses on an irrelevant

issue to detract attention from the real issue.

• A Red Herring is literally a SMELLY FISH. You basically say, “My back is against the wall. I cannot win this argument. HERE IS AN AWFUL SMELLY FISH TO DISTRACT YOU!

– Mom, I know I have ISS for tardies but at least I am not doing drugs like all those other kids up there!

Circular Reasoning/ Begging the Question

• An argument in which the writer, instead of applying evidence simply restates the point in other language.– God exists. How do you know? The Bible

says so. Who wrote the Bible? God. – Chicken nuggets are good. Why are they

good? Because they are tasty. Why are they tasty? Because they are good!

FALSE AUTHORITY

The person presenting the argument is an authority, but not on the subject at hand.

Three types:Self Proof—”Because I said so”Spokes Person—”Because famous person says

so”Too much Credit—”Because they are good at

one thing, they know all things”

I have a degree in Medicine and I am here to tell you the economy is about to FAIL!

I have a degree in Medicine and I am here to tell you the economy is about to FAIL!

Bandwagon• “Everyone has it”

Bandwagon

• Threat of rejection is substituted for evidence, desire to conform to beliefs of a group.

Loaded Words

• Using highly connotative words to describe favorably or unfavorably without justification.

Non Sequitur (Does Not Follow)

• A conclusion that does not follow logically from preceding statements. Or the train of thought jumps the tracks at some point.– Mary loves children, so she will make an excellent

school teacher. (This support alone does not follow or is Non-Sequitor—If Mary is a murderer, or has a 50 IQ, she will not make a good teacher no matter how much she loves kids.)

– No one should grill their steaks. Cows don’t like smoke. (This does not follow because it does not make sense. The cows are dead. They are steaks.)

SLIPPERY SLOPE• Like a muddy hill, if we go down this slope we will fall • If we allow one thing a whole slew of other, negative

events will occur as a resultEx. If we allow students to have ipods, pretty soon they

will have entire systems out in class bumping bass all over the school.

Ex. If we pass this health care bill eventually the government will take over the decision-making from patients and doctors

STRAW MAN• The person attacks an argument which is different from, and

usually weaker than, the opposition's best argument. Ignores a person’s actual position and substitutes an exaggerated or distorted version.

– Setting up a fake version of something or someone that is easy for others to not like.

– Ex. Katie, my shih-tzu, isn’t really hungry; she just wants us to get up all the time and cater to her every whim!

– People who think abortion should be banned have no respect for the rights of women. They treat them as nothing but baby-making machines. That's wrong. Women must have the right to choose.

• Discrediting what a person might later claim by presenting unfavorable information in advance.

• Senator Creavey was once arrested for tax evasion.

Poisoning the Well

Oversimplification• Tendency to provide simple solutions to

complex problems.

Ex.To avoid drunk driving accidents restaurants

should just stop selling alcohol.