informal fallacies

Fallacy
 Refers to errors of reasoning.
 Fallere – to deceive
 Formal Fallacy – committed mainly due to lack of skill in reasoning, and this in turn is due to lack of training in the logical process
 Informal Fallacy – committed when either irrelevant psychological factors are allowed to distort the reasoning process or when one is confused by linguistic ambiguities in one’s premises and conclusions.

A. Fallacy of Language

1. Equivocation
a. A king moves one square in any direction
But, Solomon is a king
Ergo, Solomon moves one square in any direction
b. Gambling should be legalized because it is something we can’t avoid. It is an integral part of human experience; people gamble every time they get in their cars or decide to get married.
c. “Boy” rhymes with “toy”
but you have a boy
ergo, you have a toy.

2. Amphiboly – awkward construction of one’s sentence allows a multiple interpretation.
a. To be repaired: the rocking chair of an old lady with two broken legs.
b. Wanted: A man to take care of a dog that does not smoke or drink.
c. Not seeing the patrol car, the car sped up.
d. Going up the stage, the crowd applauded the newly elected President.
e. If Croesus goes to war with Cyrus, he would destroy a mighty kingdom.

3. Fallacy of Accent
Arises from a false accent or from a false emphasis in speech.

A dessert is a course of fruit served after the meal. But, a desert is a forsaken region. Ergo, a forsaken region is a course of fruit served after meal.
Newspaper headline: “President to Declare Martial Law.”
The poster says: : Recycle clothes and waste paper.
3 day Sale – 75% off / FREE FAN

4. Fallacy of Composition
Consists in taking collectively what should be taken individually.

Since every part of a machine is light in weight, the machine as a whole is light is weight.
Manny Pacquiao is a boxer. He is a Filipino. Ergo, all Filipinos are boxers.
Since the cost for printing a book is relatively cheap, the book as a whole must also be relatively cheap.
One person can carry a wheel. That wheel is a part of my car. Therefore, one person can carry my car.

5. Fallacy of Division
Consists in taking individually what should be taken collectively

All diamond rings inside the jewelry box cost over 100 million pesos…
Everything in this room weighs about 1000 lbs…
A ballpen can write …
The family of Mr. Belen is very musical, Barry therefore, must be musically inclined.
La Sallians are handsome. Junn Aranate, a La Sallian, must be handsome.
An average Filipino family has 4 children. Tenirefe’s family is average. Therefore, she has 3 other siblings.

6. Fallacy of Word Construction
Infers a similarity of meaning from the similarity of the material pattern of the two words.

Infinite means without limit;
indefective means without defect;
ergo, indebted means without debt.
B. Fallacy of Relevance

1. Accident – what is true as a general rule is also true in some special cases. Also, when one confuses the substance with accidents.
All good soldiers should obey their superior’s orders…
We have to be generous…
One has to tell the truth always …
Principle of Confidentiality … (priest)

2. Petitio Principii (Begging the Question)
All criminals are immoral. Ergo, all criminals are not moral.
Why are you here? Because I’m not there!
We must not drink liquor. Why do you say that? Drinking is against the will of Allah. How do you know? The Koran says so. But how do you know that the Koran says right? Everything said in the Koran is right. How do you know that? Why, it’s all divinely inspired. But how do you know that? Why, the Koran itself declares that it is divinely inspired. But why believe that? You’ve got to believe the Koran, because everything in the Koran is right.

3. Argumentum ad Hominem (Attack against man)
You are very extravagant!
How about you? You have been extravagant yourself
You say I’m not pretty; Look who’s talking.
You should not listen to her opinion. She has been a drug-addict and has also been arrested due to theft.
Rasyl: Why were you late again in our class, Aubrey?
Aubrey: Look who’s talking. Last week you have been late twice, remember?
I saw and heard the candidate on TV last night. I shall not vote for him because he has lost his good looks.

4. Argumentum ad Populum (Appeal to People)
Our exams should be postponed, sir! The majority of the class have agreed to it.
“The war-mongering character of this flood of propaganda is very clear. But the shining reputation of our nation is impervious to slander, and we shall persevere.”
“It is beyond dispute that since Sanchez was implicated in the Sarmenta-Gomez case, the mass media have been regarding him as the most nefarious, notorious and abominable human being God ever created. How sure are we then that Judge Demetriou had not in the least been affected by the media pressures strengthened by the public’s outcry? ... I only want to remind the people that not all who have been convicted are really guilty; in the same manner that not all who have been acquitted are, in fact, innocent.” – from a reader of PDI Juliet Villar

5. Argumentum ad Misericordiam (Appeal to Pity)
A student should be given a passing grade because he is soon to graduate, or because if he fails his parents would kill him.
We cannot condemn this man because he is the only one that supports his family.
Where will the suspect’s poor wife get financial support for her family if you convict him? Where is your sense of justice, your sense of humanity? Where is your sense of compassion? How can you bear to see this poor man’s children suffer and eventually starve to death?
There was a youth who was tried for a particularly brutal crime – the murder of his mother and father with an axe. Confronted with an overwhelming proof of his guilt, he pleaded for leniency on the ground that he was an orphan.


6. False Cause
Say what you will! I’m not going to let a black cat cross my path. Noel let one cross his path and shortly thereafter his house caught on fire.
Frauline won lotto when she attended Mr. Belen’s class. Therefore, you should attend Mr. Belen’s class to win in the lotto.
He met an accident because it was Friday the 13th.
She sings in the kitchen; therefore, she will remain an unmarried woman all her life.
After he broke the bedroom mirror yesterday morning, he had a car accident that afternoon. Indeed, breaking a mirror is bad luck.
Ira received a text from a friend telling her to send it to 10 people and her love life will be happy. She said that last month she sent the text to 10 people and after a week her boyfriend became very intimate and caring to her. Ira should better send this text to 10 of her friends now.

7. Argumentum ad Verecundiam (Appeal to Misplaced Authority)
Aikken: These pills must be safe and effective for reducing.
Ritchel: What made you say that?
Aikken: My manicurist told me so.

Jose Javier Reyes, director of the movie “Live Show,” said in a press conference that MTRCB has unjustly banned the movie from being shown. According to Reyes, the movie is not pornographic since it has a very relevant plot and a well-written story line. Since Reyes is a veteran in Philippine cinema, we can say that indeed MTRCB acted wrongly in banning the said movie.

8. Argumentum ad Baculum (Appeal to Force)
“Agree with me or you’ll never get anything from me anymore.”
Demy to Sarah: “Be home by 9pm or you can forget about the increase in allowance next week.”
“Earl! You better agree to my proposal or you won’t see your family anymore.”
“Students! Keep quite! If not, all of you will fail in Logic!”

9. Appeal to Advantage
Rhegine offers Adrian, a government official, a huge amount provided he facilitate or give a favorable decision on some transactions in which Rhegine has some interest.
Allen Peter, a rich man, offers to pay the hospital bills of a beautiful young girl’s sick mother, provided the girl allows herself to be his mistress.
Gene, a religious political leader offers Inno a job, provided Inno joins Gene’s religion and accept his beliefs.

10. Argumentum ad Ignorantiam (Appeal to Ignorance)
Committed when one argues that something must be true on the basis that it has not been proven false, or false on the basis that it has not been proven true.

Kriss is a paragon of honesty because he has never been caught cheating by any of her teachers.
Faith healing must work; no one has ever been able to prove that it doesn't.
Gian believes that there are living creatures in Mars called Martians. Nobody can furnish evidence to disprove his contention, so it must be true.