Fallacies

 

LEARNING FLOW IN LOGIC

Testing 1 

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Deductive Inductive

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Deductive Valid Sound Inductive 

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 Arguments

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Strong Cogent

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Deductive Symbolic Logic Truth Table

Testing 3

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Testing 2

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Inductive Fallacy

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Basic Principle in Logic

 ARGUMENT  ARGUMENT

 ARGUMENT

support the conclusion

 Premises that do not support the conclusion

 Good

 Bad reasoning

 Premises that

reasoning

 

 What is a Fallacy?

Bad argument

Error in reasoning

Deceptive  Argument

 

Fallacy is ...  An argument that seems to be correct but actually is not because either the premise is false or the conclusion is false.

y

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 Any form of argument that shows inconsistency or falsity.

 

Two Gr oups oups of Fallacy  Deductive

Formal

Argument

Informal

 Inductive argument

 

Causes of Fallacy in Inductive Argument Content

of 

the Premises

Conclusion Emotions Pejorative Discredit Disposition

 

Types of Fallacies Irrelevance

Weak

Presumption

Ambiguity

Grammatical

Induction

Analogy

Appeal to Pity

Appeal to unqualified Authority

Begging the question

Appeal Force to

Appeal to Ignorance

omplex Question

Appeal to People

Hasty Generalization

False Dichotomy

Equivocation

C

Argument False Cause against person Accident

Irrelevant Conclusion

Weak Analogy

Suppressed Evidence

Composition

D

Amphiboly

ivision

 

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Fallacies of Irrelevance 1.  Appeal

to pity 2.  Appeal to force 3.  Appeal to the people 4.  Argument against person 5.  Accident  6. Irrelevant Conclusion a. b. c.

Straw Man Missing the Point  Red Herring

 

 Appeal to Pity (Argumentum ad Misericordiam) Example: The accused is a father of five children. All of them will be deprived of the care of a father, will stop from schooling, no one to feed them because the wife is jobless. Thus, he should be acquitted from the penalty.

I should not fail in Logic class. I have been taking it up for three consecutive times now. now. My father is working abroad doing all the sacrifices and hard work to be able to send me to school. Moreover, Moreover, if my father knows about this, he will surely beat me m e to death.

 

 Appeal to Force (Argumentum ad Baculum) Example: The members of League of Filipino Students will go to the streets to rally and demonstrate. There will be chaos in the streets. Therefore, the plea of the LFS to halt the tuition fee increase must be heeded.

Those who do not join the gimmick will no longer be considered as part of the peer group. Friends are friends. All for one, one for all. So, everyone must skip classes this afternoon to play dota.

 

 Appeal to Emotion (Argumentum ad Populum) 1.

Popular Appeal

Marian Rivera says that Sunsilk shampoo makes her her hair shiny shiny and beautiful. She is a movie actress and a model. Sunsilk Sunsilk shampoo shampoo will will make my hair shiny and beautiful.

2.

Appeal to the Multitude

Everyone is selfish; everyone is doing what he believes will make himself happier. happier. The recognition of that can take most of the sting out of  accusations that you're being "selfish." Why should you feel guilty for  seeking your own happiness when that's what everyone else is doing, too?

Many people nowadays no longer give importance to virginity virginity.. So, S o, virginity is a thing of the past.

 

 Attack against person

(Argumentum ad Hominem)

1.

Abusive The candidate promised that he will do everything so that the cleanliness of the barangay barang bar angay ay wil willl be attained. attained attai ned.. He cannot cannot cann ot do itit because he cannot even removed his beard and clean his face. (Therefore, the candidate cannot fulfill his promise).

The teacher files complaints against the student for f or cheating during class. He should not be listened to because he is at odds against his colleagues and he is not welcome to his department because of his ill temper. 2. Circumstantial

 Abortion is immoral. This position is widely accepted among am ong the priest because they have to or they will be reprimanded by the pope to whom they pledged obedience.

 

Fallacy of Accident 

Examples: Freedom of Speech is a constitutionally guaranteed right. Therefore, Jose Ma. Sison should not be arrested arr ested for his speech that  incited the riot last week. Property should be returned to its rightful r ightful owner. That drunken student who is starting a fight with his opponent in the canteen lent  you his kitchen knife and now he wants it back. Therefore, you should return it to him now. Bestfriends help one another in all undertakings. There will be a written exam in Logic L ogic class today. Therefore, we should sit together and help each other pass the exam.

 

Irrelevant

Conclusion (Ign gnoratio gnor orati atio o Elenchi) Elenc Ele nchi hi)

1. Missing the point Crimes of  of car carnap carnapping nappin ping g and murder murder have have been increasing increa inc reasin sing g at an alarming rate lately. The conclusion is obvious, we must reinstate the death penalty immediately. The bicameral form of government is not effective effective in the Philippines. Therefore, we should shift to the parliamentary form of government. There are some provisions in the 1986 Constitution that are no longer attuned to the 21st  century. They oftentimes serve as barrier to the socio--economic socio -economiceconomic-political -political advancement of the country. Therefore, we must advocate for the change of the constitution.

 

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2.

Red Herring

There is a good deal of talk these days about the need to eliminate pesticides from our fruits and vegetables. But many of the foods are essential to our health. Carrots are an excellent source of vitamin A, broccoli is rich in iron, and oranges o ranges and grapefruits have lots of  vitamin C. Pres. GMA will run after the hoodlum in uniforms and the crooks in robes. Policemen and judges are two professions that take a long years of education to achieve it. And, they need to have a license in order for them to practice their profession. Meralco charges high Meralco high electricity electricity rate because because they impose on the consumer their operation cost, retirement plan and benefits of their employees. The spokesperson of  of Meralc Meralco o claimed claimed that that it would have not happened if the government would abolish the value added tax being imposed on private establishments.

 

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3.

Straw Man

DLSC Teachers proposed to start the classes with prayer. This is a clear case of of proselytization. proselytization. Therefore, the school intends to convert its student to the catholic faith.

The garment workers have signed a petition arguing for better ventilation on the work premises. Unfortunately, air conditioning is expensive. Air ducts would have to run throughout the factory, and a massive heat exchange unit installed on the roof. Also, the cost of  operating such a system during the summer would be astronomical. In view of these considerations, the petition must be rejected. The SC presented the guidelines for school dress code. What they want is for the students to return to the ancient era when women and men alike wear clothes from neck down. Such a policy is ridiculous.

 

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Fallacies of Weak induction  Appeal to unqualified Authority 10.  Appeal to ignorance 11. Hasty Generalization 12. False Cause 9.

- Non causa causa pro pro causa causa - Pos Postt hoc ergo ergo propter propte propterr hoc - Slippery Sl Slip ippe pery ry Slope Sl Slop ope e 13.

Weak Analogy

 

 Appeal to Unqualified U nqualified Authority (Argumentum ad Verecundiam) 

Examples: Dr. De La Cruz, our family f amily physician, has stated that the creation of  muonic atoms of deuterium and tritium hold the key to producing a sustained nuclear fusion reaction at room temperature. In view of Dr. De La Cruz expertise as a physician, we must conclude that this is indeed true.

Mr. Lucio Tan, owner of Fortune For tune Tobacco in the country, testified before the congressional factfact -finding -finding committee that tobacco is not an addictive substance and that smoking cigarettes does not produce pr oduce any addiction. Therefore, we should believe him and conclude that  smoking does not in fact lead to any addiction.  An old man who is practically pr actically blind has testified in court that he saw the defendant stab the victim with a bayonet while he was standing in the twilight shadows 100 yards from the incident. Therefore, the defendant must be found guilty.

 

 Appeal to Ignorance (Argumentum ad Ignorantiam) 

Examples: People

have been trying for centuries to provide conclusive evidence evidence for the claims of astrology, astrology, and one hasthat everastrology succeeded. we mustno conclude is lotTherefore, of nonsense. People

have been trying for centuries to provide conclusive evidence evidence to disprove the claims of  astrology, and no one has ever succeeded. Therefore, we we must m ust conclude that the claims of  astrology are true.

 

Hasty Generalization (Converse Accident) 

Examples:  After one year the alternator went out in Mr. Juan De La Cruz new Toyota altis. Ms. De Limas new Toyota Ava altis.  Avanza Avanza nza develo developed ped a transmissio transm transmission ission n problem after six months. The obvious conclusion is that cars manufactured by Toyota Motors are just a pile of junk these days.

Six Arab fundamentalists were convicted of bombing the World Trade Center in New York City. The message is clear: Arabs are nothing but a pack of  religious fanatics prone to violence.

Lea Salonga a name abroad andthe in the th e US scene an a reliable reli singer and all actress. Billy made Crawford has conquered music in able Europe. Indeed, Filipinos are great artists.

My parents had premarital sex, and still ended up with each other. My uncle and auntie had the same experience but they are having a wonderful marriage. So, it is alright to have premarital sex.

 

False Cause (Post hoc ergo propter hoc; Non ca caus causa usa a pro pro causa) causa) 

Examples:

Whenever I play basketball with my kneecap on, I play like Michael Jordan. To bag the MVP award in the next tournament, I should always play with my kneecap on. When students are assured of a high grade, the learning curve is higher because the pressure and anxiety are eliminated. Therefore, we must eliminate the grading system to ensure an efficient  educational program. The quality of education in the Philippines is on a decline for years. Clearly, the teachers just are not doing their job jo b these days. Today, all of us can look forward to a longer life span than our parents and grandparents. Obviously, we owe our thanks to the millions of dedicated doctors who expend every effort to ensure our health.

 

Slippery Slope 

Examples: Immediate steps should be taken to outlaw pornography once and for all. The continued manufacture and sale of  pornographic material material will almost certainly lead to an increase in sex related crimes such as rape and incest.

This result and in turninwill an gradually increase in erode crimes theofmoral all sorts. fabric Eventually of societya complete disintegration of law and order will occur, leading in the end to the total collapse of civilization.  Attempts to outlaw pornography threaten basic civil rights and should be summarily abandoned. If pornography is outlawed, censorship of newspaper and news magazines is only a short step away. After that there will be censorship of textbook, political speeches, and the content  of lectures delivered by university professors. Complete mind control by the central government will be the inevitable result.

 

Weak 

Analogy

Examples: Michaels new car is bright blue, has leather upholstery, and gets excellent mileage. Johns new car is also bright blue and has leather upholstery. Therefore, it probably gets excellent gas mileage, too.

Lasallia Lasa Lasallian llian n student student A is tall, dark dark and handsome. handsome. handsom e. Lasallian Lasallian student B is tall and dark. So student B is more likely handsome.

Philippines is an archipelago, located in south east Asia, a third world country and predominantly catholic. Indonesia is an archipelago, located in south east Asia, and a third world country. So probably, Indonesia is predominantly Catholic.

 

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Fallacies of Presumption 15. 16. 17.

Begging the Question Complex Question False Dichotomy

18. 

Suppressed Evidence Fallacies of Ambiguity 19. Equivocation

20. 

 Amphiboly Fallacies of Grammatical Analogy 21. Composition 22. Division

 

Begging the Question (Petitio Principii) 

Examples: Murder is morally wrong. This being the case, it follows that abortion is morally wrong.

It is obvious that the poor in this country should be given handouts from the government. After all, these people earn less than the average citizen. Capital punishment is legitimate and appropriate. Thus, capital punishment is justified. Ford Motor Company clearly produces the finest cars in the US. We We know they produce the finest cars because they have the best design engineers. This is true because they can afford to pay them more than the other manufacturers. Obviously, they can afford to pay them more because they produce the finest cars in the US.

 

Complex Question 

Examples: Have you stopped cheating on exams?

Where did you hide the cookies you stole?

 Are you going to be a good little boy and eat your hamburger? hambur ger?

Is George Hendrix still smoking marijuana?

How long must I put up with your snooty behavior?

 

False Dichotomy 

Examples:

Either you let me attend the Lady Gaga concert or Ill be miserable for the rest of my life. I know you dont want  me to be miserable for the rest of my life, so it follows that youll let me attend the concert. Either you use Rexona Rexona deodorant deodorant or or you risk risk the chance chance of  perspiration odor. Surely you dont want to risk the chance of perspiration odor. Therefore, Therefore, you will want to use Rexon Re Rexona xona a deodorant. deodo de odoran rant. t. Either you buy only FilipinoFilipino-made -made products or you dont  deserve to be called a loyal Filipino. Yesterday you bought  a MexicanMexican-made -made plipplip- plops slippers. slippers. Therefore Therefore There fore it is clear clear that you dont dont deserve deserve to be called called a loyal loyal Filipino.

 

Suppressed Evidence 

Examples:

Most dogs are friendly and pose no threat to people who pet them. Therefore, it would be safe to pet the little dog that is approaching us now.

The Philippines currency has increased increased it value against  against  the dollar because of the sound economic agenda of Pres. GMA administration. Therefore, Therefore, the country is on the way to economic recovery. The Bible states in one passage that Judas hanged himself. in another passage, Go and do the same. Therefore, let us go and hanged ourselves.

 

Equivocation 

Examples: Some triangles are obtuse obtuse.. Whatever is obtuse is ignorant. Therefore, some triangles are ignorant.  All strikes areare protests. All strikes are good pitches. Therefore, some good pitches protests. Every pen is a writing instrument. The cage of a pig is a pen pen.. Therefore, the cage of a pig is a writing instrument. We have a duty to do what is right . We have as right  right to to speak out in defense of the innocent. Therefore, we have a duty to speak out in defense of the innocent.

 

 Amphiboly 

Examples: The tour guide said that standing in Greenwich Village, the Empire State Building could easily be seen. It follows that the Empire State Building is in Greenwich Village.  All hospital patients carrying an umbrella have broken ribs. Professor Ocampo said that he will give a lecture about heart failure in the biology lecture hall. The paralytic student sat on a chair with a broken leg. Woman without her man is a savage.

 

Composition 

Examples:

Michelle likes vanilla ice cream. She also likes chocolates. Therefore, it is certain that she would like vanilla ice cream dipped in chocolates. Each atom in this piece of chalk is invisible. Therefore, the chalk is invisible. Sodium and chlorine, the atomic components of salt, are both deadly poisons. Therefore, salt is a deadly poison.

7 is odd, 5 is odd. But 7 and 5 are twelve. Therefore, 12 is odd.

 

Division 

Examples: Salt is a nonpoisonous compound. Therefore, its component elements, sodium and chlorine are non poisonous. This when assembled, is circular in shape. Therefore, eachjigsaw piece ispuzzle, circular in shape. The Royal Society is over 300 years old. Prof. Mag Magsad Magsadia sadia ia is a mem member ber of the Royal Society. Therefore, Prof. Magsa Magsadia dia is over 300 years old.  All in this room weigh 1 metric ton. But, only John is in this room. Therefore, John weigh 1 metric ton.

Twelve is even. But 7 and 5 are twelve. Therefore, 7 and 5 are even.

 

Detecting Fallacies

Attention to what the arguer is saying. Listeners or readers must not be asleep, passive, drugged on that state. W hat are the Emphasis: What is the conclusion? What reasons given in support of the conclusion? conclus ion?

Relevance: Are the reasons relevant to the conclusion? Do the reasons support conclusion? conclusion?

Think!!!

the

 

Avoiding Fallacies There is a need for moral education Familiarity with every fallacies Check

and control of one¶s emotions

Acknowledge one¶s worldview Critique

one¶s presuppositions

 

END

 

Exercise: Analyze each one and indicate what kind of fallacy is described in each number. 1. Every butter butterfly fly is an an insect. Some flies are big. Ergo, some some people people are laborers. 2. You are are seated seated beside beside a woman. woman. Ergo, she is your lover lover.. 3. All men men are thinking thinking beings. Some men desire desire attractiv attractive e women. women. Ergo, Ergo, those who desire attractive women are thinking beings. 4. I did not see your girlfriend girlfriend ever since. since. Ergo, you have have no girlfriend. girlfriend. 5. The car car accident did not occur occur because because it is not read read in the the newspaper newspaper.. 6. She is a two-ti two-timer mer and irresp irresponsible onsible woman woman.. I hope she will turn turn out to be a good wife. 7. Beli Believe eve me or or else else you you will will b be e sorry sorry.. 8. This blouse blouse is colorful because it has orange, orange, blue, blue, white, white, purple, purple, red, red, yellow and green on it. 9. Som Somebod ebody y died died beca because use of your your dream dream..

 

Exercise: Analyze each one and indicate what kind of fallacy is described in each number. 10. I am not going to listen to your negative statements regarding my future wife. All I want to hear from you are words of praises. 11. My ring is i s missing. You You are one of the many who went near me. Ergo, you stole my ring. 12. You You never talk to me. Ergo, you are mute. 13. You You are unlucky unluc ky today because it¶s Friday the 13th. 14. All babies are adorable. Some babies are a re black. Ergo, sugar is sweet. 15. There are no spirits because we don¶t don¶ t see them.

 

Informal Fallacies Emotions Discredit/Pejorative Dispositions