Proof substitute A word or phrase that suggests the speaker has a proof, but no proof is
actually offered.
Qualifier A word or phrase that restricts or limits the meaning of other words.
Random sampling Choosing a sample so that at every choice there is an equal chance for
any of the remaining members of the population to be picked. Compare Haphazard
sampling.
Reasoning in a chain with all Reasoning in the form: All S are P; all P are Q; so all S
are Q. Valid.
Reasoning in a chain with almost all Reasoning in the form: Almost all S are P; almost
all P are Q; so almost all S are Q. Usually weak.
Reasoning in a chain with conditionals Reasoning in the form: If A, then B; if B, then C;
so if A, then C. Valid. See also Slippery slope argument.
Reasoning in a chain with some Reasoning in the form: Some S are P; some P are Q;
so some S are Q. Usually weak.
398 GLOSSARY
Reasoning from hypotheses If you start with an assumption or hypothesis A that you
don't know to be true and make a good argument for B, then what you have established is
"If A, then B . "
Reducing to the absurd Proving 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.
Refuting an argument Showing an argument is bad.
Refuting an argument directly
• Show that at least one of the premises is dubious.
• Show that the argument isn't valid or strong.
• Show that the conclusion is false.
Relevance To say that the premises of an argument are irrelevant just means that the
argument is so bad you can't see how to repair it. See also Irrelevant premise.
Repairing arguments See Guide to Repairing Arguments, Unrepairable arguments.
Representative sample A sample in which no one subgroup of the whole population is
represented more than its proportion in the population.
Sample See Generalizing.
Shifting the burden of proof Saying that the other person should disprove your claim,
rather than proving it yourself.
Slanter Any literary device that attempts to convince by using words that conceal a
dubious claim.
Slippery slope argument An argument that uses a chain of conditionals, at least one of
which is false or dubious. A bad form of reducing to the absurd.
Some Often taken to mean "at least one." Sometimes "some" is best understood as
"at least one, but not all."
Sound argument A valid argument with true premises.
Statistical generalization A generalization that says that the same proportion of the whole
as in the sample will have the property under discussion.
Strawman An attempt to refute a claim or argument by arguing against another claim
that's easier to show false or an argument that's easier to show weak. Putting words in
someone's mouth.
Strong and weak arguments Invalid arguments are classified on a scale from strong to
weak. An argument is strong if it is possible but unlikely for the premises to be true and the conclusion false (at the same time). An argument is weak if it is possible and likely for the premises to be true and the conclusion false (at the same time).
Structural fallacy An argument whose form alone guarantees that it is a bad argument.
Subjective claim A claim whose truth-value depends on what someone (or something)
thinks, believes, or feels. A subjective claim invokes personal standards.
GLOSSARY 399
Subjectivist fallacy Arguing that because there is a lot of disagreement about whether a
claim is true, it is therefore subjective.
Sufficient condition See Necessary and sufficient conditions.
Support A claim or claims that gives some reason to believe another claim.
Tests for an argument to be good
• The premises are plausible.
• The premises are more plausible than the conclusion.
• The argument is valid or strong.
Truth-value The quality of being true or false.
Two times zero is still zero A numerical comparison that makes something look
impressive, but the basis of comparison is not stated.
Unbiased sample See Representative sample.
Uncontrolled experiment: cause-to-effect An experiment to establish cause in a
population. Two randomly chosen samples are used. In one the cause is (apparently)
present, in the other (apparently) not, and they are followed over time.
Uncontrolled experiment: effect-to-cause An experiment to establish cause in a
population. A sample of the population in which the effect is present is examined to see
if the cause is also present and other possible causes are not present.
Unrepairable arguments We don't repair an argument if any of the following hold:
• There's no argument there.
• The argument is so lacking in coherence that there's nothing obvious to add.
• A premise it uses is false or dubious and cannot be deleted.
• Two of its premises are contradictory, and neither can be deleted.
• The obvious premise to add would make the argument weak.
• The obvious premise to add to make the argument strong or valid is false.
• The conclusion is clearly false.
Up-player A word or phrase that exaggerates the significance of a claim.
Vague sentence A sentence for which there are so many ways to understand it that we
can't settle on one of those without the speaker making it clearer.
Valid argument An argument in which it is impossible for the premises to be true and the
conclusion false (at the same time).
Weak argument See Strong and weak arguments.
Weaseler A claim that is qualified so much that the apparent meaning is no longer there.
Wishful thinking A feel-good argument used on oneself.
Answers to Selected Exercises
Chapter 1
1. Convincings/arguments.
3. We can convince others; others can convince us; we can convince ourselves.
4. a. Yes.
b. Yes, but truth-value depends on who says it (looking forward to Chapter 2).
e. No, a command.
g. I could never figure out who was supposed to be in need. It's too unclear for me to classify it
as a claim,
i. Yes.
k. Yes, but it might not have the same truth-value as (j).
n. Depends on your view of what "true" means. Some might say "No," thinking that there's no way we could ever determine whether it is true or false. Others will argue that it is true or
false, independently of us. That's philosophy.
7. To convince (establish) that a claim, called the "conclusion," is true.
8. Given an argument, the conclusion is the claim that someone is attempting to establish is true, while the premises are the claims that are used in trying to establish that.
9. Commands, threats, entreaties ("Dr. E, Dr. E, please, please let me pass this course"), etc., are not arguments.
12. Depends on whether she's talking to herself. We can't tell. Arguments use language.
14. Argument? Yes.
Conclusion: You shouldn't eat at Zee-Zee Frap's restaurant.
Premise: I heard they did really badly on their health inspection last week.
NOTE: The premise isn't "They did really badly on their health inspection last week."
Someone hearing that it's so and its being so aren't the same claim.
16. Argument! No.
/> 20. Argument! No. No conclusion is stated (though it's implicit—we'll talk about when we're justified in supplying a missing conclusion in Chapter 4).
27. Virtue.
Chapter 2
Section A
2. b. O.K.
d. O.K. Just because you don't know what the entire cost is doesn't mean it's vague.
h. O.K. It's just a funny way of saying "Jane is really attractive."
j . Too vague.
1. Too vague (but see the next section).
4. It's an example of the drawing the line fallacy.
7. b. Ambiguous. Rumsfeld himself lacks intelligence. Intelligence agencies don't have enough
information.
c. Americans—individually or collectively? Compare Example 3, p. 16.
g. Each player on the team had a B average. The average of all the grades of the members of
the team was B.
i. Vague, not ambiguous.
400
•
Answers to Selected Exercises 401
10. c. Ambiguity due to the words "protect" and "valuable": Anything that's commercially valuable should be kept from harm or loss.
11. This appears to be an example of a drawing the line fallacy. But it'snot. The mistake here is that there is a simple way to draw the line: It's excessive force if the suspect is hit when he is no
longer resisting.
12. Ms. Hathaway is (implicitly) arguing that she was justified in allowing her 7-year-old daughter to fly across the country. You might believe her, until you realize she is trading on the vagueness of
the words "freedom," "choice," and "liberty" (try to pin down what you think those words mean).
Section B
1. a. Subjective = Its truth-value depends on what someone or something thinks/believes/feels.
b. Objective = Its truth-value does not depend on what anyone or anything thinks/believes/
feels (= not subjective).
c. No.
4. When describing our own feelings we don't have awfully precise language to use. So "It's hot"
may be the best we can do in describing how we feel. But it's inadequate as an objective claim.
6. a. Objective.
d. Subjective (even though Dr. E thinks it's objective and true).
i. Objective in the Middle Ages, when people believed demons existed. Now probably
understood as demons in the mind, so subjective,
j. Objective, since "insane" is now a technical term of the law.
Section C
2. Prescriptive or descriptive! Prescriptive, since we shouldn't do what is evil. Standard needed!
Yes. But it's not clear what's intended, so we shouldn't accept it as a claim until one is given.
3. Prescriptive or descriptive'! Descriptive. Standard needed? No.
4. Prescriptive or descriptive? Prescriptive. Standard needed? Yes. Either one of Exercise 3 or 4 will do, but until one is chosen we shouldn't view it as a claim.
11. Prescriptive or descriptive? Descriptive. Standard needed? No, it's just a subjective value judgment. Unless the clerk happens to be an art history major or ex-art history professor, .. .
in which case see the answer to Exercise 12.
12. Prescriptive or descriptive? Not clear until a standard is given. Standard needed? Yes. Is this meant as objective, and that you should like Picasso better than Rembrandt? Or is it
meant as just a subjective value judgment?
Section D
1. c. Persuasive definition.
d. Definition. No longer classifies correctly, but it once did.
f. Not a definition.
4. The definition and the original phrase can be used interchangeably, and the words in the
definition are clear and better understood than the words doing the defining.
5. Because they settle a debate before it's started. They are concealed claims.
Exercises for Chapter 2
1. All the possibilities are: claim + objective ambiguous or too vague + not a claim
claim + subjective persuasive definition + claim + objective
definition + not a claim persuasive definition + claim + subjective
3. Definition, not a claim.
7. Objective claim.
12. Too vague, not a claim.
402 Answers to Selected Exercises
Chapter 3
Sections A-C
4. No. The premises could be false. Even if the premises are true, they might be less plausible
than the conclusion.
5. a. Come up with a (possibly imagined) situation in which the premises are true and the
conclusion false,
b. Come up with a (possibly imagined) likely situation in which the premises are true and the conclusion false.
7. Nothing.
14. No. A false conclusion shows the argument is bad. But the argument could still be valid (it
would have at least one false premise then).
16. No. Invalid arguments are classified from strong to weak.
17. Bad. (Not necessarily weak—it could be valid.)
19. d. 20. d. 21. c. 22. d 23. d. 24. c.
Exercises for Chapter 3
I. Nothing.
4. No. See the parakeets example in Section B.
6. Conclusion: Flo got a haircut.
Premises: Flo's hair was long. Now Flo's hair is short. ("So" is not part of the conclusion.) Invalid: Flo might have gotten her hair caught in a lawn mower. But it's strong. Good if
premises are plausible.
10. Valid and good.
12. Weak, bad. Spot could be a penguin or a cockroach.
16. This is bad because it's begging the question.
17. Not an argument.
18. Weak, bad. They might want to hire conservatives for balance. Or conservatives are hired, but
they become liberal over time. Or Maria just hasn't met enough professors.
19. Valid and good if premises are plausible. (Maybe Dick bought it on credit? Then the first
premise is false.)
23. Weak. Professor Zzzyzzx may have changed his grading, or the school may have required him to
become harder, or he may just never have had a student as bad as Suzy.
Chapter 4
Sections A-D
8. Nothing.
10. a. i. premise, ii. premise, iii. premise, iv. conclusion
b. i. conclusion, ii. premise, iii. premise, iv. premise
f. i. premise, ii. premise, iii. conclusion
I I . Deleting it doesn't make the argument weaker, and no obvious way to link it to the conclusion.
The most common errors in the following exercises
•Repairing arguments that are unrepairable.
•Adding premises that don't make the argument better or make a whole new argument.
• Adding a premise and then marking the argument moderate or weak. The only reason to add a
premise is to make the argument valid or strong.
•Marking both "valid" and "strong" or both "valid" and "weak."
•Marking an argument "weak" when it's bad (valid or strong with a dubious premise).
Answers to Selected Exercises 403
In many answers only premise(s) that are needed are given. When a premise is added, the argument is
good (if the premises are plausible), unless noted otherwise.
12. Conclusion: Dr. E is a man. Premises: Dr. E is a teacher. All teachers are men.
Valid, bad, unrepairable: The second premise is false.
13. "Anything that walks like a duck, looks like a duck, and quacks like a duck, is a duck" or
" I f it walks like a duck, looks like a duck, and quacks like a duck, it's a duck."
16. Conclusion: You didn't get the flu from me.
"The person who shows symptoms of the flu first got the flu first. If you get the flu first, you can't have gotten it from someone who didn't have it." Valid.
The first added premise is probably false, but it's the only way the argument could be repaired.
So the argument is unrepairable.
You can't add "The person who shows symptoms of the flu first probably got the flu first."
The word "impossible" indicates the speaker thinks he/she is making a valid argument, so you can't repair it as a strong argument.
18. This is an argument: You can't ignore what the speaker intends, and "so" shows the speaker meant it as an argument. Can't be repaired (see Example 2).
19. Too much missing. Can't be repaired without making a new argument entirely. But it is an
argument. See the comments for Exercise 18.
20. "Ralph barks." Good argument if this is plausible.
21. "(Almost) the only way you can inherit blue eyes is if both your parents are blue-eyed" is the obvious premise to add to make the argument valid. But that's false. So it's unrepairable.
25. Conclusion: The burgers are better at Burger King. Premises: "The bigger the burgers the better the burgers." "The burgers are bigger at Burger King." The latter is not obviously true, and anyway, bigger than what? Bigger than at other fast-food places? Which ones? Too vague.
Even if true, whether the argument is good depends on whether you agree with the first premise,
which is subjective.
28. Not an argument. If you try to interpret it as an argument, it's hopelessly bad, and that should
convince you not to think of it as an argument.
3 1 . Conclusion: "Cigarettes are not a defective product that causes emphysema, lung cancer, and other illnesses." The premises in the quote contradict each other, so the argument is bad.
Section E
1. a. The guy she's talking to is fat. b. She thinks I'm fat.
6. She was driving within a couple miles from her home—even though she had macular
degeneration, Parkinson's disease, and Alzheimer's! [And that should scare you a lot!]
Chapter 5
Sections A and B.1
2. Accept as true, reject as false, suspend judgment.
3. Because it's impossible for the premises to be true and the conclusion false.
6. No. It's just the experience of other people.
9. We have good reason to doubt our memory, or the claim contradicts experiences of ours and there
is a good argument (theory) against the claim. Also, beware of confusing memory with
deductions from experience.
15. Our memory.
16. Nothing.
17. The same attitude we had before we heard the argument. An argument with a false premise tells
Richard L Epstein Page 50