Critical Thinking Chapter 6

lOMoARcPSD|359 747 69
How many legs does this elephant have? 1 lOMoARcPSD|359 747 69 Is it moving? 2 lOMoARcPSD|359 747 69 3 lOMoARcPSD|359 747 69 Fallacies
1. Fallacies What of Relevance mistake!!!
2. Fallacies of 4 Insufficient Evidence lOMoARcPSD|359 747 69 What is a Fallacy?
 A (logical) fallacy is an argument that
contains a mistake in reasoning.
 Fallacies can be divided into two general types:
 Fallacies of Relevance
Arguments in which the premises are logically irrelevant to the conclusion.
 Fallacies of Insufficient Evidence Arguments
in which the premises, though logically relevant
to the conclusion, fail to provide sufficient evidence for the conclusion. 5 lOMoARcPSD|359 747 69 statement is true or false A statement is to another RELEVANT
statement if it provides at least some
reason for thinking that the second . lOMoARcPSD|359 747 69 Fallacies of Relevance
 There are three ways in which a statement
can be relevant or irrelevant to another:
1. A statement is positively relevant to another
statement if it provides at least some reasons for
thinking that the second statement is true.  Example:
- Dogs are cats. Cats are felines. So dogs are felines.
- All dogs have five legs. Rover is a dog. So Rover has five legs. 7 lOMoARcPSD|359 747 69 Fallacies of Relevance 8 lOMoARcPSD|359 747 69
2. A statement is negatively relevant to another
statement if it provides at least some reasons for
thinking that the second statement is false. Example:
- John is a high-school senior. So, John likely has a Ph.D.
- Mai is two years old. So, Mai probably goes to college. 9 lOMoARcPSD|359 747 69 Fallacies of Relevance
3. A statement is logically irrelevant to another
statement if it provides no reason for thinking that the
second statement is either true or false.  Example:
- The earth revolves around the sun. Therefore,
marijuana (one type of drugs) should be legalized. 10 lOMoARcPSD|359 747 69
- Last night I dreamed that the Vietnamese
Football team win the World Cup. Therefore,
the Vietnamese Football team will win the World Cup. Fallacies of relevance
 Do exercise 5.1 in page 121. Exclude examples.
 Write answers in paper and submit as 11 lOMoARcPSD|359 747 69 homework. Date: Group: … Homework: 5.1 Answer: 2. … 3… 5… … Fallacies of Relevance
 A fallacy of relevance occurs when an arguer
offers reasons that are logically irrelevant to his or her conclusion. 12 lOMoARcPSD|359 747 69
 Eleven Fallacies of Relevance:
1. Personal Attack 7. Bandwagon
2. Attacking the Motive Argument
3. Look Who’s Talking 8. Straw Man
4. Two Wrongs Make a Right 9. Red Herring
5. Scare Tactics 10. Equivocation
6. Appeal to Pity 11. Begging the Question 13 lOMoARcPSD|359 747 69 1. Personal Attack
Personal Attack (Ad Hominem)
When an arguer rejects a person’s argument
or claim by attacking the person’s character
rather than examining the worth of the
argument or claim itself.
1. X is a bad person.
2. Therefore X's argument must be bad. 14 lOMoARcPSD|359 747 69 Pattern
1. Personal Attack - Examples
 "Bill says that we should give tax breaks to
companies. But he is untrustworthy, so it must be wrong to do that."
 Dr. Smith’s books about plant genetics are
worthless because he used to tell a lie at high school. 15 lOMoARcPSD|359 747 69
 Sam is divorced, so how can he make sound
financial decisions for the city? 1. Personal Attack 
Not every personal attack is a fallacy Example:
Mai has testified that she saw my client rob the Bank. But
Ms. Mai has twice been convicted of perjury. In addition,
you’ve heard Ms. Mai’s own mother testify that she is a
pathological liar. Therefore, you should not believe Ms.
Mai’s testimony against my client. 
The fallacy of personal attack occurs only if:
(1) An arguer rejects another person’s argument or claim 16 lOMoARcPSD|359 747 69
(2) The arguer attacks the person who offers
the arguments or claim, rather than
considering the merits of that argument or claim.
2. Attacking the Motive
Attacking the Motive
When an arguer criticizes a person’s motivation
for offering a particular argument or claim,
rather than examining the worth of the
argument or claim itself. 17 lOMoARcPSD|359 747 69
1.X has biased or has questionable
motives. 2. Therefore, X’s arguments or
claim should be rejected. Pattern
2. Attacking the Motive Examples
Professor A has argued in favor of academic
tenure. But why should we even listen to Prof. A? As
a tenured professor, of course he supports tenure. 18 lOMoARcPSD|359 747 69
2. Attacking the Motive
 Not all attacks on arguer’s motives are
fallacious Example:
 Burton Wexler, spokesperson for the American Tobacco
Growers Association, has argued that there is no credible
scientific evidence that cigarette smoking causes cancer.
Given Wexler’s obvious bias in the matter, his
arguments should be taken with a grain of salt. 19 lOMoARcPSD|359 747 69
3. Look Who’s Talking
Look Who’s Talking (tu quoque – And you, too)
When an arguer rejects another person’s argument
or claim because that person is a hypocrite. Example:
My Dad’s always telling me not to talk on my mobile
phone while I’m driving, but why should I take any
notice of him? He’s always taking calls when he’s driving.
1. X fails to follow his or her own advice. 18 Pattern
2. Therefore, X’s claim or argument should be rejected. lOMoARcPSD|359 747 69
3. Look Who’s Talking 21 lOMoARcPSD|359 747 69
 It should be noted, however, that there is nothing
fallacious as such in criticizing a person’s hypocritical behavior. Example:
 Jim: Our neighbor Joe gave me a hard time again
yesterday about washing our car during this drought emergency.
Patty: Well, he’s right. But I wish that hypocrite
would live up to his own advice. Just last week I saw
him watering his lawn in the middle of the afternoon. lOMoARcPSD|359 747 69
4. Two Wrongs Make a Right
Two Wrongs Make a Right
When an arguer attempts to justify a
wrongful act by claiming that some other act
is just as bad or worse. Examples:
“I don’t feel guilty about cheating on Prof. A’s online quiz.
Half the class cheats on his quiz.”
“Why pick on me, officer? Everyone else is using drugs.” 23 lOMoARcPSD|359 747 69
1. Others are committing worse or equally
bad acts. Pattern 20
2. Therefore my wrongful act is justified.
4. Two Wrongs Make a Right
 Bill has borrowed Jane's expensive pen, but
found he didn't return it. He tells himself that it is
okay to keep it, since she would have taken his.
 Mother: Honey, it’s wrong to steal. How would
you feel if someone stole your favorite doll? lOMoARcPSD|359 747 69
Child: But you told me you stole your friend’s
teddy bear when you were a little girl. So
stealing isn’t really wrong.
both: (4) two wrongs make a right and
(3) look who’s talking 5. Scare Tactics Scare Tactics
When an arguer threatens harm to a reader or
listener and this threat is irrelevant to the truth
of the arguer’s conclusion. Example: 25 lOMoARcPSD|359 747 69
Gun lobbyist to politician: This gun-control bill is
wrong for America, and any politician who
supports it will discover how wrong they were at the next election.
Fear is a powerful motivator – so powerful that it Remember 22
often causes us to think and behave irrationally. 5. Scare Tactics 
Not all threats involve fallacies.
Example: Parent to teen: If you come home
late one more time, your allowance will be cut. lOMoARcPSD|359 747 69 
President John Kennedy to Soviet Premier
Nikita Krushchev: If you don’t remove your
nuclear missiles from Cuba, we will have no choice
but to remove them by force. If we use force to
remove the missiles, that may provoke an all-out
nuclear war. Neither of us wants a nuclear war.
Therefore, you should remove your missiles from Cuba. 27 lOMoARcPSD|359 747 69 6. Appeal to Pity Appeal to Pity
When an arguer attempts to evoke feelings of pity or
compassion, where such feelings, however understandable,
are not relevant to the truth of the arguer’s conclusion.  Example:
Student to Lecturer: I know I missed half your classes and failed
all my quizzes and assignments. First my cat died. Then my
girlfriend told me she has found someone else. With all I went
through this semester, I don’t think I really deserve an F. Any
chance you might cut me some slack and change my grade to a C or a D? 28 lOMoARcPSD|359 747 69 6. Appeal to Pity
1. P is presented, with the intent to create pity. Pattern
2. Therefore claim C is true. 29 lOMoARcPSD|359 747 69 6. Appeal to Pity  Example:
“Chúng tôi cảm nhận sâu sắc về vấn ề ạo
ức ngành y, hy vọng các ại biểu và nhân
dân nhìn nhận khoan dung với chúng tôi .
Một năm ngành y khám bệnh cho 121 triệu
lượt người, một con số lớn như thế nên
không thể tránh khỏi những sơ xuất.” 30
1.P is presented, with the intent to create pity. lOMoARcPSD|359 747 69 6. Appeal to Pity 
Not all arguments that contain emotional appeals fallacious. Example: 
"I should receive an 'A' in this class. After all, if
I don't get an 'A' I won't get the fellowship that I want." 
"I'm positive that my work will meet your requirements.
I really need the job since my grandmother is sick." 
Professor: "You missed the midterm, Bill."
Bill: "I know. I think you should let me take the makeup." Professor: "Why?" 31 lOMoARcPSD|359 747 69 6. Appeal to Pity
Bill: "I was hit by a truck on the way to the midterm.
Since I had to go to the emergency room with a broken
leg, I think I am entitled to a makeup."
Professor: "I'm sorry about the leg, Bill. Of course you can make it up.“ 32 lOMoARcPSD|359 747 69 7. Bandwagon Argument
Bandwagon Argument (Peer Pressure)
When an arguer appeals to a person’s desire to be popular,
accepted, or valued, rather than to logically relevant
reasons or evidence. Example:
- All the really cool IU students use iPhone. Therefore, you should, too.
- All cool students dye hair and wear shorts to school.
You must change your style right away! 33 lOMoARcPSD|359 747 69
Pattern 12. Most (or a select group of) people believe or do
X.. Therefore, you should believe or do X. 7. Bandwagon Argument Example:
“Lúc ấy tôi thấy bia “vô chủ”, nhiều người lấy nên cũng vô tư
làm theo. Đến khi công an vào cuộc iều tra chúng tôi lo sợ,
cảm thấy xấu hổ với những người thân, hàng xóm. Từ khi bị
công an mời lên, tôi rất hối hận và sợ hãi", anh Cường kể lại.
“Thực sự tôi nhặt bia với tâm
lý ám ông chứ không nghĩ
mình ang hôi của. Sống hơn
nửa cuộc ời rồi và giúp rất nhiều 34 lOMoARcPSD|359 747 69
người khi bị rơi tài sản
xuống ường, vậy mà chỉ
một phút mất tỉnh táo, tôi ã phạm
sai lầm", bị can Vinh nói. 7. Bandwagon Argument 
Not all appeals to popular beliefs or practices are fallacious. Example: 
All the villagers I’ve talked to say that the water is
safe to drink. Therefore, the water probably is safe to drink. 35 lOMoARcPSD|359 747 69 
Lots of my friends recommend the Back
Street Deli, so it’s probably a good place to eat.
Premises are relevant to the conclusions No fallacy!!! 36 lOMoARcPSD|359 747 69 8. Straw Man Straw Man
When an arguer misrepresents another person’s
position to make it easier to attack. Example:
Pete has argued that the New York Yankees are a better
baseball team than the Atlanta Braves. But the Braves
aren’t a bad team. They have a great pitching staff, and they
consistently finish at or near the top of their division.
Obviously, Pete doesn’t know what he’s talking about.
1. X’s view is false or unjustified [ but where X’s view
has been unfairly characterized or misrepresented ]30 Pattern
2. Therefore X’s view should be rejected. lOMoARcPSD|359 747 69 8. Straw Man  Person A has position X.
 Person B presents position Y ( which is a distorted version of X).
 Person B attacks position Y.
 Therefore X is false/incorrect/flawed. Example:
 Evolution is false! How could a mouse evolve into 38 an elephant!? lOMoARcPSD|359 747 69 9. Red Herring Red Herring
When an arguer tries to sidetrack his audience
by raising an irrelevant issue, and then claims that
the original issue has been effectively settled by
the irrelevant diversion.
1. Topic A is under discussion.
2. Topic B is introduced under the guise of
being relevant to topic A (when topic B is
actually not relevant to topic A). 39 lOMoARcPSD|359 747 69
Pattern 3. Topic A is abandoned. 9. Red Herring  Example:
 "I think there is great merit in making the
requirements stricter for the graduate students.
I recommend that you support it, too. After all, we
are in a budget crisis and we do not want our salaries affected." 40 lOMoARcPSD|359 747 69
 You’re not being fair by denying me the
opportunity to have a make-up test. I’m paying for this course! 9. Red Herring  Example:
 "I think there is great merit in making the
requirements stricter for the graduate students.
I recommend that you support it, too. After all, we
are in a budget crisis and we do not want our salaries affected." 41 lOMoARcPSD|359 747 69
 You’re not being fair by denying me the
opportunity to have a make-up test. I’m paying for this course! 9. Red Herring
 It is not a fallacy simply to change the subject or evade an issue. Example:
 Political opponent: Congressman Crookley, now that
you have been convicted of bribery, extortion, and
grand theft auto, isn’t it high time that you resigned from office? 42 lOMoARcPSD|359 747 69
Representative Crookley: How’ bout those
Yankees? A ten-game lead at the All-Star break!
no mistake in reasoning in the argument, no
fallacy is committed (the speaker does not deny the charge!) 43 lOMoARcPSD|359 747 69 10. Equivocation Equivocation
When an arguer uses a key word in an argument in two
(or more) different senses.  Example:
 It is crime to smoke grass. Kentucky bluegrass is a grass.
Therefore, it is a crime to smoke Kentucky bluegrass.
 Any law can be repealed by the proper legal authority. The
law of gravity is a law. Therefore, the law of gravity can be
repealed by the proper legal authority.
Fallacies of Equivocation can be difficult to spot Remember 36
Because they often appear valid, but they aren’t. lOMoARcPSD|359 747 69
11. Begging the Question
Begging the Question
When an arguer states or assumes as a premise (reason)
the very thing he is seeking to probe as a conclusion. Example:
God is perfect because this is what the Bible says.
The Bible cannot be wrong because it is the word of a perfect God.
Arguing in a circle 45 lOMoARcPSD|359 747 69 Reason
– A because B, B because A. lOMoARcPSD|359 747 69
11. Begging the Question Examples 47 38 lOMoARcPSD|359 747 69
Bill: "God must exist." Jill: "How do you know." Bill: "Because the
Bible says so." Jill: "Why should I believe the Bible?" Bill: "Because the Bible was written by God."
Document Outline

• Fallacies of Relevance
• Fallacies of relevance
  • Fallacies of Relevance
  • 1. Personal Attack
    • Personal Attack (Ad Hominem)
  • 1. Personal Attack - Examples
  • 1. Personal Attack (1)
  • 2. Attacking the Motive
    • Attacking the Motive
  • 2. Attacking the Motive Examples
  • 2. Attacking the Motive (1)
  • 3. Look Who’s Talking
  • 4. Two Wrongs Make a Right
    • Two Wrongs Make a Right
  • 4. Two Wrongs Make a Right (1)
  • 5. Scare Tactics
    • Scare Tactics
  • 5. Scare Tactics (1)
    • Appeal to Pity
  • 7. Bandwagon Argument
    • Bandwagon Argument (Peer Pressure)
  • 7. Bandwagon Argument (1)
  • 7. Bandwagon Argument (2)
  • 8. Straw Man
    • Straw Man
  • 9. Red Herring
    • Red Herring
  • 9. Red Herring (1)
  • 9. Red Herring (2)
  • 9. Red Herring (3)
  • 10. Equivocation
    • Equivocation
  • 11. Begging the Question
    • Begging the Question
  • 11. Begging the Question Examples