conclusion. OR you could say, "I hadn't thought of that. I guess you're right." OR you could say, "I'll have to think about that."
7. Sex is the answer to almost everyone's problems.
Unsubstantiated claim. Dick's "Why? " asks for support. It's an invitation to Zoe to give an argument.
It takes away your tension.
Zoe offers support for her conclusion.
It doesn't if you're involved with someone you don't like.
Dick shows her support is false or dubious.
Sex makes you feel better.
Zoe gives up on that support and offers another.
It doesn't if it's against your morals. Heroin makes you feel good.
Dick's first comment shows Zoe's claim is dubious. His second comment shows that the
relation of Zoe's claim to the conclusion is weak (he's challenging the unstated premise
"If it feels good, it's good to do").
It's healthy and natural, just like eating and drinking.
Zoe gives one last try to support her conclusion.
You can catch terrible diseases. Sex should be confined to marriage.
Dick shows that support is dubious, too. Then he asserts his own view, which is somewhat
supported by his previous claims.
10. Unrepairable.
11. Showing that at least one of several claims is false or dubious, or collectively they are
unacceptable, by drawing a false or unwanted conclusion from them.
13. Ridicule is not an argument.
15. It's a bad argument.
16. a. Putting words in someone's mouth. Refuting an argument or claim that the other person
didn't really say.
19. Reducing to the absurd. Whether it's effective depends on what unstated premises are added to
make it valid or strong. If the other person accepts capital punishment, it might be effective.
20. Tom's presented a strawman. Lee is for equal rights, not preferences. Tom has a common
misconception, identifying equal rights laws with affirmative action programs. Doesn't refute.
21. This shows how important it is to master the material in this chapter if you want to be a
good CEO. We can classify this hopelessly bad attempt at a refutation as blustering.
Chapter 8
Section A
1. Dogs eat meat. Every dog eats meat. Everything that's a dog eats meat.
2. At least one cat swims. There is a cat that swims. There exists a cat that swims.
5. Everything that flies is a bird.
6. No one who is a police officer is under 18 years old. All police officers are not under 18 years
old. Not even one police officer is under 18 years old. Nothing that's a police officer is under 18
years old.
7. Dogs and only dogs are domestic canines.
8. Nothing that's a pig can fly. Pigs can't fly.
9. c. Don't confuse this with "Some textbooks fall apart after one semester." You cannot know this from your personal experience unless you've worked for a publisher.
Answers to Selected Exercises 411
d. False. I've seen Crest in some stores.
10. (There are other correct answers.)
a. Some student doesn't like to study.
b. Some woman is a construction worker.
c. Some CEO of a Fortune 500 company is not a man.
d. This exam will not be given in some of the sections of critical thinking.
e. Some exam is suitable for all students.
f. All exams really test a student's knowledge.
g. All drunk drivers get in accidents.
h. Some donkeys don't eat carrots.
i Some people who die young aren't good.
j. Someone who is a teacher is not allowed to grade exams or someone who grades exams is not
a teacher,
k. Something both barks and meows.
1. Tom is not suspended, and he will not start some football game.
m. There is a football player who is a vegetarian and his coach doesn't hate him. (See Chapter 6.)
n. Some decisions about abortions should not be left to the woman and her
doctor,
o. Some cowboy had a friend named "Tonto," and the cowboy wasn't the Lone
Ranger.
11. a. Sometimes when Dr. E is irritated with his students he doesn't give an exam.
b. Sometimes it rains in Seattle in July.
c. Spot will always chase Puff.
d. There are flocks of birds along the river at times other than in the winter.
Section B
1.
2.
3.
4.
5.
6.
Answers to Selected Exercises
7. c. 9. c. 11. d. 13. d.
8. d. 10. c. 12. d. 14. d.
15. Invalid. Lee could be one of the ones who does attend lectures. Not every ? every not.
16. Not valid.
17. Valid.
18. Invalid. No picture, but it could be that dogs bite only postal workers who are
cowardly and would never bite back, and the postal workers who bite dogs are so tough
they never get bitten. So there's no postal worker and dog that bite each other.
19. Invalid.
21. Invalid.
23. Invalid. George could be mute.
25. Invalid.
26. Invalid. The premise is not "All hogs grunt." Don't mistake your knowledge of the world for what's actually been said. It's reasoning in a chain with "some."
30. Valid. No picture. Dr. E has a dog. That dog must love its master. So that dog loves Dr. E.
So Dr. E is loved.
31. Invalid. Only janitors have access does not mean that all janitors have access. Paul could be one of the day janitors who doesn't have access.
33. For example,
a. If it's a cat, then it coughs hair balls.
b. If something is a donkey, then it eats hay.
c. If something is made of chocolate, it's good to eat.
d. If it's a duck, then it likes water.
Section C
1. All but a very few teenagers listen to rock music. Nearly every teenager listens to music. Only a
very few teenagers don't listen to rock music.
2. Almost all adults don't listen to rock music. Very few adults listen to rock music. Almost no
adult listens to rock music.
Answers to Selected Exercises 413
3. Strong.
4. Not strong. Arguing backwards with "very few."
5. Not strong. Here's a picture drawn to scale.
6. Strong.
7. Strong.
8. Strong.
9. Strong.
12. Weak, reasoning in a chain with "almost all."
13. Strong.
Review Exercises for Chapters 6-8
1. An argument is a collection of claims, one of which is called the "conclusion," and the others of which, called the "premises," are meant to establish or prove that the conclusion is true.
2. The premises are plausible. The premises are more plausible than the conclusion. The argument
is valid or strong.
3. A valid argument is one for which it is impossible for the premises to be true and the conclusion
false (at the same time).
4. A strong argument is one for which it is almost impossible for the premises to be true and
the conclusion false (at the same time).
5. No. The premises could be false or it could beg the question. You should provide an example of
a bad valid argument.
6. Provide a likely example where the premises are true and the conclusion false.
7. No. It could beg the question. You should provide an example.
8. A compound claim is one that is made up of other claims, but which has to be viewed as just one
claim.
10. a. The contradictory of a claim is another claim that must have the opposite truth-value.
11. Yes.
12. A false dilemma is an "or" claim that seems to be true but isn't, because there is another possibility that it does not state.
13. Yes. 15. No.
14. Yes. 16. No.
17. No. It could be a slippery slope argument.
18. a. "A is a necessary condition for B" means that " I f B, then A" is true.
19. It helps you avoid making your argument weak, and it shows others that you have considered the
other side.
20. Show that one of the premises is dubious; show that the argument isn't valid or strong; show that the conclusion is false.
21. Only if the additional premises you have used are all true and the argument is valid. If the
additional premises are only plausible, or the argument is only very strong, you've only shown
that it's very likely that one of the original premises is false or collectively they lead to an
absurdity.
22. A slippery slope argument is bad and doesn't refute.
23. Ridicule is not an argument.
31. Excluding possibilities. The direct way of reasoning with "all."
The direct way of reasoning with conditionals. Reasoning in a chain with "all."
The indirect way of reasoning with conditionals. The direct way of reasoning with "no."
Reasoning in a chain with conditionals.
414 Answers to Selected Exercises
32. Affirming the consequent. Reasoning in a chain with "some."
Denying the antecedent. The direct way of reasoning with "almost all."
Arguing backwards with "all." Arguing backwards with "almost all."
Arguing backwards with "no." Reasoning in a chain with "almost all."
Chapter 9
14. Weaseler: Zoe didn't apologize!
16. This implies but does not state that in our part of the world people don't react with emotions and wouldn't be so easily manipulated as the Arabs, which is false.
19. There is no slanter in this highly disparaging remark about foreign-exchange dealers. It's all
upfront ridicule.
21. Hyperbole: The whole forest?
23. Weaseler: He didn't say it was the most important message, but if. . . .
24. "Despite" is an up-player. Why "despite"?
26. "Gaming" is a euphemism for "gambling." Sure you'd say, "Honey, let's go out gaming tonight."
33. Euphemism: unspoiled wilderness area = uninhabited area.
35. Weaseler: This is not an apology for interfering with his course, but an attack on the professor's standards: He's the cause of the problem because he's male.
38. Implies without proof that junkies, rape, and bad families are "real life." But no slanters.
40. Qualifier: at present.
4 1 . Euphemisms: resettled = forcibly moved to and internment camps = prison camps (it's a
dysphemism to call them "concentration camps"). Innuendo: at last.
44. Concealed claim: seat belts protect from injury / she was lucky not to be injured when not
wearing a seat belt. But in this case the concealed claim is true.
Chapter 10
8. Zoe's argument: appeal to pity. Premise: You shouldn't experiment on animals if you feel sorry
for the dogs.
Dick's argument: appeal to spite. Premise: You should experiment on cats if they make me
sneeze.
9. Feel-good argument. Bad.
14. Appeal to patriotism (subspecies of feel-good argument). Generic premise: You should believe
that democracy is the best form of government if you love the U.S. (and think it's the greatest
country). Bad argument.
17. Appeal to fear. You might think it's O.K. because a senator is supposed to worry about how his
votes will be perceived by his constituents. But it's bad: We have a representative democracy, so a senator is supposed to vote as he or she thinks best. And the children whose votes the writer
is threatening the senator with aren't voters yet.
19. Appeal to fear. Without more premises it's bad.
20. Wishful thinking. Bad. That way of thinking may be useful, though, to motivate the person to
lose weight.
Chapter 11
1. The argument must be valid or strong; we must have good reason to believe its premises; the
premises must be more plausible than the conclusion.
4. No. It could beg the question, or a premise could be implausible even though true.
5. Only if the false premise can be eliminated and the argument remains strong.
6. Nothing.
Answers to Selected Exercises 415
7. Our own experience.
8. The argument has a valid form. It's just that some of the premises are false or collectively too
dubious.
9. It's a valid argument form. But the "or" claim is false or dubious.
10. An attempt to reduce to the absurd is pretty clearly an argument. With ridicule there's no
argument at all.
29. A strawman is putting words in someone's mouth, attempting to refute an argument by refuting a
different one.
30. Because they are also clearly bad ways to convince, though they aren't arguments.
Short Arguments for Analysis
These are just sketches of answers, enough for you to see how to fill them out.
2. Shifting the burden of proof. Bad. But you probably knew that even before reading it.
4. Dick's response to Zoe's comments looks like an attempt to reduce to the absurd; but not enough
argument is given, so it's just ridicule.
5. Not an argument; there's no attempt to convince.
7. Tom's argument has a prescriptive conclusion: You should get a small pig. Everything he says
may be true, but it won't get him the conclusion unless he has some prescriptive premise. You
figure out what that should be and if it's plausible.
Dick makes an argument that Lee shouldn't accept Tom's argument. Dick is mistaking the
person for the argument.
9. Conclusion: Maria's alarm didn't go off. Premise: She's stili asleep. Unstated premise:
If Maria's still asleep, her alarm clock didn't go off. Direct way of reasoning with conditionals.
Good.
12. Shifting the burden of proof: The candidate who's speaking has to show inflation is a serious risk.
14. Powell is making an argument with conclusion (unstated/reworded), "Working with
toxic chemicals is not exceptionally dangerous." This leads into Chapter 12, since it
depends on a very faulty analogy. Bad, possibly wishful thinking.
16. Lee is refuting Tom's argument by reducing to the absurd. Good refutation.
19. It looks like Zoe is concluding that these cookies will be awful. If so, it's reasoning in a
chain with "some," and it's bad.
20. Conclusion: You should employ Mr. Abkhazian as your lawyer.
Premise: He's been doing accident cases for 20 years.
Unstated premises: If he's been doing accident cases for 20 years, he's good at doing that. You
should go to someone who's good at accident cases.
Bad argument. First unstated premise is dubious.
22. Suzy draws a conclusion from Zoe's comment: You don't care about people.
Weak and no way to make it stronger. Bad.
23. Strawman (Ms. F is putting words in the student's mouth). Bad.
28. Premises: Israel had 23 casualties. The combat took a long time.
Conclusion: Great efforts were made by the IDF to conduct the operation carefully in an effort to
bring to an absolute minimum the number of Palestinian civilian casualties.
Unstated premises: Israel has a huge military ad
vantage. Israel could just heavily bomb the
refugee camp at Jenin. If a military operation in an urban setting takes a long time and the
strong attacking force has a number of casualties, then a great effort was made to keep civilian
casualties to a minimum.
The last premise is implausible (a conditional form of a false dilemma), unless "great effort"
means doing anything other than bombing a refugee camp flat. Since we can assume that the
416 Answers to Selected Exercises
people in the IDF can reason, this appears to be evidence that they don't adhere to the Principle of
Rational Discussion.
31. Appeal to pity. With an unstated prescriptive premise, it's good.
32. Bad appeal to authority. The attorney general has motive to mislead. It's just too much to think
that a political appointee never lies and always investigates thoroughly. But that's not to say the
conclusion is false!
33. This conspiracy theory illustrates that possibility * plausibility. The Interior Minister has given no reason to believe anything he's said. This is so bad that it's either an attempt to confuse
people, or it shows that the Saudi minister can't reason. Either way, don't bother to engage him
in rational discussion.
40. With appropriate unstated premises, it's excluding possibilities, and it's good.
42. Ridicule. Bad. Or it's reducing to the absurd, and good, depending on what Lee believes.
43. Begging the question.
44. Bad. Reasoning backwards with "all": Only tenants have a key = All people who have a key are tenants. Harry might be one of the tenants who doesn't have a key.
45. DOGS ARE GOOD. CATS ARE BAD.
46. Conclusion: Suzy or one of her friends will get a contract. Reasoning in a chain with "some."
Bad.
48. Implied but unstated: Women heads of credit unions are not qualified—otherwise, Headlee would
see that there are plenty of women in Utah who are qualified. Convincing without an argument
with innuendo. Bad.
49. We can make this argument fairly strong by adding premises: "Society should do what it can to prevent young people from engaging in sexual activities before they are emotionally prepared and
before they understand the health risks." "Young people who know about the mechanics of sex will not be as likely to engage in risky sexual activities." "Teaching young people to refrain from sexual intercourse will lessen the likelihood that they will engage in sexual intercourse before
they are emotionally prepared."
Richard L Epstein Page 52