Critical Thinking:A User’s Manual

Chapter 5Detecting Fallacies

Fallacies

A fallacy is a common mistake in reasoning.Often are rhetorically persuasive

Begging the Question

Occurs when the truth of the conclusion is assumed by the argument’s premises.“Some claim is true because that claim is true.”

Smoking is bad for you because it is so unhealthy.

P:

Issue:

Your Turn!

Why are arguments that beg the question bad arguments?

Appeal to Ignorance Fallacy

Occurs when the arguer illegitimately shifts the burden of proof:“I am right because no one has proven otherwis

e.”Does not occur when the burden of proof is

placed correctly:What is the “burden of proof”?Who has the burden of proof?

Neither you nor anyone else can prove that the Loch Ness Monster doesn’t exist. Obviously, then, it must.

P:

Issue:

No one has ever proven that ghosts exist. Therefore, ghosts do not exist.

P:

Issue:

Your Turn!

When is an argument that shifts the burden of proof to the other side not a fallacy?

Distinguishing Begging the Question from Appeal to Ignorance

Begging the Question

P: C C

Issue: Whether C is true

Appeal to Ignorance

P: ~ C has not been proven C

Issue: Whether C is true

Appeal to Illegitimate Authority

Occurs when the arguer cites a source, which is not an authority on the subject in question:“Some claim is true because an “expert” said it

was true.”Does not occur when the source is a

legitimate authority. What counts as a legitimate authority?

Acai Berry is the solution to weight problems and sexual dysfunction. After all, that’s what Oprah Winfrey says.

P:

Issue:

Lap-Band is an effective solution for weight loss. After all, Dr. J. Clay Wellborn Jr., a bariatric surgeon in Little Rock, says so.

P:

Issue:

Lap-Band is an effective tool for weight loss. I know because out of 2,000 of Lap-Band surgeries performed by J. Clay Wellborn, all resulted in significant weight reduction when combined with a good diet and exercise plan.

-- Oprah Winfrey

P:

Issue:

Your Turn!

How can you determine when an argument that specifies the identity of the speaker appeals to authority?

Ad Hominem

Occurs when the arguer rejects an opponent’s conclusion on the basis of his or her characteristics:“You should not accept some claim because it was

said by person x and person x is biased, hypocritical, crazy, or the like”

Does not occur when the opponent offers testimony or when the issue is about the opponent.

Jim argues that Bristol Palin should be voted off Dancing with the Stars because she is the worst dancer on the show. But we shouldn’t listen to Jim. After all, he’s a democrat.

P1: P2:

Issue:

Craig says that he’s the best choice for the head of the Environmental Protection Agency, but I disagree. Before he entered the government, he spent years as an attorney protecting toxic polluters and oil companies who wanted to drill in environmentally sensitive areas.

P:

Issue:

Your Turn!

How do you decide whether an ad hominem argument is a fallacy or a legitimate argument?

Distinguishing Appeal to Illegitimate Authority from Ad Hominem

Appeal to Illegitimate Authority

P: (Illegitimate) P says C C

Issue: Whether C is true

Ad Hominem

P1: P argues for CP2: P is biased, crazy,

hypocritical, etc. ~ C

Issue: Whether C is true

Strawman Fallacy

Occurs when the arguer misrepresents the opponent’s viewpoint, and then attacks the argument in its distorted form.“My opponent argues that X, but you should

not accept (distorted version of) X because…”

Issue does not match the conclusion

Many people have argued that women’s college athletics should receive as much financial support as men’s. It’s just not right to let women be the only athletes at the university. Fewer people would go to games if all they could see were women play, and men are just as dedicated to sports as women are.

P1: P2:

Issue:

Red Herring Fallacy

Occurs when the arguer distracts you by providing premises that are irrelevant to the conclusion:“You should accept X because…hey, look

over there!”

Karen thinks that Domino’s Pizza makes better pizza than Pizza Hut, but did you realize that the owner of Domino’s, Tom Monaghan, has made huge financial contributions to extremist organizations like Operation Rescue? Obviously, Karen is wrong.

P:

Issue:

DistinguishingStrawman from Red Herring

Strawman

P: Premises ~ C (distorted)

Issue: Whether C is true

Red Herring

P: Premises (irrelevant) C

Issue: Whether C is true

Basic Analysis plus Fallacy Identification

Step 1: Write a Basic Analysis of the passage.Identify the passage.Analyze the passage.

Step 2: If it is an argument, determine whether it commits a fallacy.Identify the fallacy, and explain how it is committed.

Step 3: If it is a non-fallacious argument, diagram it.Verify that your diagram is consistent with your Basic

Analysis.

Critics of NASA’s space program contend that the money spent on space exploration could be better spent here on Earth, I whole heartily disagree. People are natural explorers, and space offers the last frontier for us to explore. Furthermore, the technology that will result from the space program will have many uses in satellite and missile defense systems.

This passage contains an argument. The issue is whether money spent on space exploration could be better spent here on Earth. The conclusion is that money spent on space exploration could not be better spent here on Earth. The first premise is that people are natural explorers. The second premise is that space offers the last frontier for us to explore. The third premise is that the technology that will result from the space program will have many uses in satellite and missile defense systems.

This argument commits the red herring fallacy. The premises given distract the reader from the issue.