Detecting Informal Fallacies

Detecting Informal Fallacies

by Luis Binala

W​hat is an informal fallacy?

It is an error ​in reasoning detectable by examining its CONTENT as opposed to formal fallacy which has error in FORM.

W​hy is it important to detect an informal fallacy?

By the definition of a fallacy, be it formal or informal, it is an error in reasoning. We ought not to rationally and morally base our assent, commitment, decision, and action on falsehood but rather on truth.

Common ​Types of Informal Fallacies

​

​Circular Reasoning

​This fallacy occurs when the arguer creates the illusion that inadequate premises provide adequate support for the conclusion—by leaving out a key premise, by restating the conclusion as a premise, or by reasoning in a circle.

Example in standard form​

​Note: (P) stands for Premise and (C) stands for Conclusion

​

(P1) Serving others is good.

(P2) It is a right thing to do.

(C) It is good to serve others.

Example in prose (common conversation)​

​

​

Violent video games cause teens to be violent, because violent teens play violent video games.

​

​Hasty Generalization

​This fallacy occurs when there is a reasonable likelihood that the sample is not representative of the group. Such a likelihood may arise if the sample is either too small or not randomly selected.

Example in standard form​

​

(P) I saw three MAVeans who bought winter melon milktea.

(C) All MAVeans like winter melon milktea.

Example in prose (common conversation)​

​

​

“Did you see that kid running through the red light? Teenagers can be such reckless drivers!”

​

​Slippery Slope

​This fallacy occurs when the conclusion of an argument rests on an alleged chain reaction, and there is not sufficient reason to think that the chain reaction will actually take place.

Example in standard form​

​

(P) You don’t plan for your future.

(C) You will not be motivated to study which will result to not getting college degree and you will end up jobless.

Example in prose (common conversation)​

​

​ “If we provide free healthcare then where does it stop? Soon people will be asking for free cars, free cell phones, free food, and free everything. The more people get free stuff, the less they will work which will eventually lead to economic ruin.”

​

​Straw Man

​This fallacy occurs when the arguer misinterprets an opponent’s position for the purpose of more easily attacking it, demolishes the misinterpreted argument, and then proceeds to conclude that the original argument has been demolished.

Example in standard form​

​

(P1) My teacher’s idea came from his religion.

(P2) He has no scientific basis.

(C) His idea is false.

Example in prose (common conversation)​

​

​ 

"Those who oppose abortion have no respect for women's rights, and see women as baby-making machines, which is of course wrong. Women must be able to choose."

​

​Ad Hominem

​This fallacy always involves two arguers. One of them advances (either directly or implicitly) a certain argument, and the other then responds by directing his or her attention not to the first person’s argument but to the first person himself.

Example in standard form​

​

(P1) She supported Duterte’s anti-drug campaign. (P2) It shows that she is pro extra-judicial killing. (C) We should not believe her argument that abortion is murder.

Example in prose (common conversation)​

​

​ “How can you argue your case for vegetarianism when you are enjoying that steak?”

​

​Appeal to Pity

​This fallacy occurs when an arguer attempts to support a conclusion by merely evoking pity from the reader or listener. This pity may be directed toward the arguer or toward some third party.

Example in standard form​

​

(P) Mr. Corrupt suffers from a lifethreatening health condition.

(C) He must be acquitted from graft and corruption.

Example in prose (common conversation)​

​

​ 

“Santa Claus must be real; it would make a lot of kids sad if he wasn’t.”

​Equivocation

​This fallacy occurs because some word or group of words is used either implicitly or explicitly in two different senses

Example in standard form​

​

(P1) We saw the evolution of cellphones.

(P2) Parasites empirically evolved.

(C) Humans obviously evolved.

Example in prose (common conversation)​

​

​ "Philosophy students are taught how to argue, but shouldn't we teach them something more helpful? After all there are already a lot of arguments and conflicts in the world."

​

Bandwagon Appeal

​This fallacy occurs when an arguer plays on certain psychological needs for the purpose of getting the reader or listener to accept a conclusion.

Example in standard form​

​

(P1) You must imitate your idols.

(P2) Your idols wear Brand X clothes.

(C) You must wear Brand X clothes, too.

Example in prose (common conversation)​

​

​ "A recent study shows 8 out of 10 doctors say that acupuncture is an effective therapy, therefore it must be true since 8 out of 10 doctors can't be wrong!"

​

Weak Analogy

​This fallacy occurs when the conclusion of an argument depends on an analogy (or similarity) that is not strong enough to support the conclusion.

Example in standard form​

​

(P1) Amber’s dog is similar in many ways to Kyle’s cat.

(P2) Both like being petted, they enjoy being around people, they beg for food at the dinner table, and they sleep with their owners. Amber’s dog loves to romp on the beach with Amber.

(C) Therefore, Kyle’s cat probably loves to romp on the beach with Kyle.

​

Example in prose (common conversation)​

​

​“If a car breaks down on a highway, a passing mechanic is not obligated to provide emergency road service. For similar reasons, if a person suffers a heart attack on the street, a passing doctor is not obligated to provide emergency medical assistance.”

​

Appeal to Force

​This fallacy occurs when the conclusion of an argument depends on an analogy (or similarity) that is not strong enough to support the conclusion.

Example in standard form​

​

(P) You better believe me or I will punch you in the nose.

(C) You should believe me that toothfairies are real.

Example in prose (common conversation)​

​

“If you don’t do what I say, I’m gonna call my big brother and he will beat you up.”

​

Appeal to Unqualified Authority

​This fallacy occurs when the cited authority or witness lacks credibility. There are several reasons why an authority or witness might lack credibility. The person might lack the requisite expertise, might be biased or prejudiced, might have a motive to lie or disseminate “misinformation,” or might lack the requisite ability to perceive or recall.

Example in standard form​

​

(P) Old Mrs. Furguson (who is practically blind) has testified that she saw the defendant stab the victim with a bayonet while she was standing in the twilight shadows 100 yards from the incident.

(C) Therefore, members of the jury, you must find the defendant guilty.

Example in prose (common conversation)​

​

"My favorite actor, who appeared in a movie about AIDS, has testified that the HIV virus doesn’t really cause AIDS and that there has been a cover-up. So, I think that AIDS must be caused by something other than HIV and the drug companies are hiding it so that they can make money from expensive anti-HIV drugs."

​

Appeal to Ignorance

​This fallacy occurs when the premises of an argument state that nothing has been proved one way or the other about something, and the conclusion then makes a definite assertion about that thing.

Example in standard form​

​

(P1) People have been trying for centuries to provide conclusive evidence for the claims of astrology, and no one has ever succeeded.

(C) Therefore, we must conclude that astrology is a lot of nonsense.

Example in prose (common conversation)​

​

“Citizens clearly favor this policy, and this policy is working. After all, I’ve never heard a single complaint since I became elected.”

​

False Dilemma

​

The false dilemma, also known as the ‘either-or-fallacy,’ is an informal fallacy that occurs when…

Someone is presented with a situation where only two options are considered when in reality, other options exist.

Example in standard form​

​

(P1) Either the world is flat or square.

(P2) The world is not flat.​

(C) Therefore, it must be square.

Example in prose (common conversation)​

​

"Would you rather invest in your future or enjoy your money now?"

​

Evaluate the following arguments​ to identify what informal fallacies they contain

​

Multiple Choice

You can't sleep tonight. Either you're in love or anxious.

• False Dilemma

• Ad Hominem

• Appeal to Pity

• Hasty Generalization

Multiple Choice

I like color blue because I like it.

• Slippery Slope

• Straw Man

• Equivocation

• Circular Reasoning

Multiple Choice

Jeff reads books everyday. He has poor eyesight. Therefore, everyone who reads a book everyday has poor eyesight.

• Bandwagon

• Hasty Generalization

• False Analogy

• Appeal to Unqualified Authority

Multiple Choice

You don't have any proof that aliens exist; thus, they don't.

• Appeal to Force

• Appeal to Pity

• Appeal to Ignorance

• Ad Hominem

Multiple Choice

Both Jack and Jill love to go up the hill. Since Jack doesn't fear falling down, Jill must not also.

• Equivocation

• Appeal to Emotion

• Slippery Slope

• False Analogy

Multiple Choice

The ice cream tastes good. Hence, it's good for my health.

• Circular Reasoning

• Equivocation

• Straw Man

• Slippery Slope

Multiple Choice

If you don't do what your friends do, you don't belong with their group. If you don't belong with their group, you are not cool. If you are not cool, then you are not famous. If you are not famous, then you are not happy.

• Straw Man

• Slippery Slope

• Appeal to Unqualified Authority

• Appeal to Emotion

Multiple Choice

She is known as a bully. Everything she says about kindness is false.

• Ad Hominem

• Appeal to Force

• Appeal to Ignorance

• Appeal to Ignorance

Multiple Choice

My parents have to buy me a new cellphone. If they don't, I will be sad and lose my interest in studying.

• Appeal to Unqualified Authority

• Bandwagon

• Appeal to Force

• Appeal to Emotion

Multiple Choice

Bernardo will break my guitar if I'll not play when he sings so I have to.

• Appeal to Unqualified Authority

• Slippery Slope

• Appeal to Force

• Bandwagon

Multiple Choice

Mrs. Dulce, a professional baker, saw me struggling in my Math homework. She told me that eating bread before studying will make my mind sharper, that's why I do so before I do my homework.

• Appeal to Unqualified Authority

• Appeal to Force

• Bandwagon

• Straw Man

Multiple Choice

Sir Luis told us that learning the basics of Logic will make us critical thinkers. We now know the basics of Logic by passing all his assessments about Logic, but still we are not critical thinkers. It shows that his idea is wrong.

• Bandwagon

• Ad Hominem

• Straw Man

• Appeal to Ignorance

Multiple Choice

You have to do a TikTok video in order to be a cool digital citizen because many have theirs.

• Appeal to Emotion

• Ad Hominem

• Bandwagon

• Appeal to Force

Conclusion​

​

A fallacy is a defect in an argument. It could be a defect in form or in content, hence the formal and the informal fallacy respectively.

In this presentation, we just covered the most common informal fallacies. Detecting fallacies equips us to be critical thinkers, thus preventing us from manipulation and deception by others’ and our own faulty reasoning. ​

​