Richard L Epstein
Page 8
c. Your reasoning is invalid.
d. I can't believe the referee made that decision. It's completely invalid.
e. Tom has a valid excuse for showing up late to football practice.
EXERCISES for Sections A-C 47
For Exercises 19-24, select the claim that makes the argument valid. You're not supposed
to judge whether the claim is plausible, just whether it makes the argument valid. These
examples may seem artificial, but we need simple practice on the definition of "validity."
19. The dogs are drinking a lot of water today. It must be hot.
a. Dogs always drink when they are hot.
b. Every dog will drink when the weather is hot.
c. Hot weather means dogs will drink.
d. Only on hot days do dogs drink a lot of water.
e. None of the above.
20. Every color monitor I've had either was defective and had to be returned, or else
burned out in less than two years. So you'd be foolish to buy a color monitor.
a. You should do what I tell you to do.
b. Every color monitor will be defective or go bad.
c. All monitors that are reliable are not color.
d. None of the above.
21. Puff is a cat. So Puff meows.
a. Anything that meows is a cat.
b. Dogs don't meow.
c. All cats meow.
d. Most cats meow.
e. None of the above.
22. Suzy is a cheerleader. So Suzy goes to all the football games.
a. Cheerleaders get in free to the football games.
b. Cheerleaders are expected to attend all football games.
c. Suzy is dating Tom, who is the football captain.
d. All cheerleaders attend all football games.
e. None of the above.
23. If Spot gets into the garbage, Dick will hit him with a newspaper. So Dick will hit Spot.
a. The garbage is a bad thing for Spot to get into.
b. Whenever Spot gets into the garbage, Dick hits him.
c. Whenever Dick hits Spot, Spot was in the garbage.
d. Spot got into the garbage.
e. None of the above.
24. The President is on every channel on television. So he must be making an important
speech.
a. Only Presidents make important speeches on television.
b. When the President makes an important speech on television, he's on every channel.
c. When the President is on every channel on TV, he's making an important speech.
d. Presidents only make important speeches.
e. None of the above.
48 CHAPTER 3 What Is a Good Argument?
D. Strong vs. Valid Arguments
Last week Lee said:
Every garbage can issued by this city that I or anyone I know has seen is blue.
Therefore, all city-issued garbage cans in this city are blue.
This is a good strong argument. Compare that to a valid argument with the same
conclusion:
This city issues only blue garbage cans.
Therefore, all city-issued garbage cans in this city are blue.
This one begs the question.
A strong argument with true premises is sometimes better
than a valid one with the same conclusion.
Folks often indicate when they make an argument that they think that it's valid
or that it's strong. For example,
Manuel says he visited Mexico. He speaks Spanish and he described the
towns he visited. So Manuel really visited Mexico.
Manuel says he visited Mexico. He speaks Spanish and he described the
towns he visited. So maybe Manuel visited Mexico.
These are the same argument: They have the same premises, and the conclusion of
both is "Manuel visited Mexico." The words "maybe" and "really" just tell us the speaker's attitude toward the argument: "so really" instead of "so maybe" lets us know the speaker thinks the argument is valid or strong, but that doesn't make the
argument valid or strong. You can't make an argument valid by calling it valid, any
more than Zoe can make Dick a pig by calling him a pig. These words are a
comment on a claim, not part of the claim.
Whether an argument is valid or strong does not depend on:
• Whether the premises are true.
• Whether we know the premises are true.
• Whether the person making the argument thinks the argument
is valid or strong.
Summary We said a good argument is one that gives good reason to believe the
conclusion is true. But we needed a standard for "good reason."
We saw that if we have no good reason to believe the premises of an argument,
or one of the premises is no more plausible than the conclusion, the argument is bad.
EXERCISES for Chapter 3 49
A good argument also needs that the conclusion of the argument follows from
the premises. We determined that meant the argument is valid or strong: Either there
is no possible way for the premises to be true and the conclusion false, or if there is
such a way, it is very unlikely.
In all, then, there are three tests an argument must pass to be good: There
should be good reason to believe its premises; it must be valid or strong; its premises
must be more plausible than its conclusion.
Depending on the conclusion we're trying to prove and the evidence we have,
we have to decide whether it's best to make a valid argument or a strong argument.
Key Words good argument valid argument
plausible claim strong argument
dubious (implausible) claim weak argument
begging the question tests for an argument to be good
Exercises for Chapter 3
1. If an argument is bad, what does that tell us about the conclusion?
2. Consider the strong argument that Dick gave that we saw above:
All parakeets anyone I know has ever seen, or heard, or read about are
under 2 feet tall.
Therefore, the parakeets on sale at the mall are under 2 feet tall.
Explain why this is better or worse than the valid argument:
All parakeets are under 2 feet tall.
Therefore, the parakeets on sale at the mall are under 2 feet tall.
3. If we want to give a good argument with a subjective claim as its conclusion, would it be
better for it to be valid or strong? Explain.
4. To prove an objective claim, should we always give an argument that is valid?
Explain or give an example.
5. Which subjects in your school would employ only valid arguments? Which would
employ primarily strong arguments? Which would rely on a mix of the two?
Here are some of Tom's answers to exercises that require all the ideas we've learned in this
chapter. He's supposed to fill in the italicized parts. Dr. E has corrected his work.
Ralph is a dog. So Ralph barks.
Argument? (yes or no) Yes.
Conclusion: Ralph barks.
Premises: Ralph is a dog.
Classify: valid strong weak
If not valid, show why:
50 CHAPTER 3 What Is a Good Argument?
Good argument? (Choose one)
• It's good (passes the three tests).
• It's bad because a premise is false.
• It's bad because it's weak.
• It's bad because it begs the question.
• It's valid or strong, but you don't know if the premises are true,
so you can't say if it's good or bad.
No! This isn't valid. Ralph might be a basenji (a kind of dog that doesn't bark].
'But it's strong,
so a good argument if the premise is true— which you don't know
for sure.
Whenever Spot barks, there's a cat outside. Since he's barking now, there must be
a cat outside.
Argument? (yes or no) Yes.
Conclusion: Whenever Spot barks, there's a cat outside.
Premises: Spot's barking now. There must be a cat outside.
Classify: valid strong X- weak
If not valid, show why: Maybe he's barking at the garbageman outside.
Good argument? (Choose one)
• It's good (passes the three tests).
• It's bad because a premise is false.
• It's bad because it's weak.
• It's bad because it begs the question.
• It's valid or strong, but you don't know if the premises are true,
so you can't say if it's good or bad.
No. The conclusion is "There is a cat outside." Ask yourself where you could put
"therefore" in the argument. 'Which claims are evidence for which others? Ihe
argument is valid but bad: The premise "Whenever Spot barks, there's a cat outside"
is implausible. Sis you point out, what about the garbageman? So it's not good.
Alison is Kim's sister, right? So Alison and Kim have the same mother and father.
Argument! (yes or no) Yes.
Conclusion: Alison and Kim have the same mother and father.
Premises: Alison is Kim's sister.
Classify: valid strong X- weak
If not valid, show why: They might be half sisters, or stepsisters, or
adopted. It depends on what the speaker means by "sister."
Good argument! (Choose one)
• It's good (passes the three tests).
• It's bad because a premise is false.
• It's bad because it's weak.
• It's bad because it begs the question.
• It's valid or strong, but you don't know if the premises are true,
so you can't say if it's good or bad.
Goodwork!
EXERCISES for Chapter 3 51
Bob has worked as a car mechanic for twenty years. Anyone who works that long
at a job must enjoy it. So Bob enjoys being a car mechanic.
Argument! (yes or no) Yes.
Conclusion: Bob enjoys being a car mechanic.
Premises: Bob has worked as a car mechanic for twenty years. Anyone
who works that long at a job enjoys it.
Classify: valid strong X— weak
If not valid, show why: Bob might not be able to get any other job.
Good argument! (Choose one)
• It's good (passes the three tests).
• It's bad because a premise is false.
• It's bad because it's weak.
• It's bad because it begs the question.
• It's valid or strong, but you don't know if the premises are true,
so you can't say if it's good or bad.
Wrong1. The argument is valid. 'What you showed is that the second premise is false
or at least very dubious. So the argument is bad, but not for the reason you gave.
the exercises below answer the following questions:
Argument! (yes or no)
Conclusion:
Premises:
Classify: valid strong weak
If not valid, show why:
Good argument! (choose one)
• It's good (passes the three tests).
• It's bad because a premise is false.
• It's bad because it's weak.
• It's bad because it begs the question.
• It's valid or strong, but you don't know if the premises are true,
so you can't say if it's good or bad.
Flo's hair was long. Now it's short. So Flo must have gotten a haircut.
Intelligent students study hard. Zoe studies hard. So Zoe is intelligent.
All cats meow. Puff is a cat. So Puff meows.
All licensed drivers in California have taken a driver's test. Dick has taken a driver's
test in California. So Dick is a licensed driver in California.
No dog meows. Puff meows. So Puff is not a dog.
Lee: I didn't get mail today and neither did Manuel or Maria. So there must not have
been any mail deliveries today.
No cat barks. Spot is not a cat. So Spot barks.
52
CHAPTER 3 What Is a Good Argument?
13. Lee: My friend Judy manages a local bookstore. She drives a new Jaguar. So bookstore
managers must make good money.
14. Dick missed almost every basket he shot in the game. He couldn't run, he couldn't
jump. He should give up basketball.
15. Dick: I got sick after eating at the school cafeteria this week.
Zoe: Me, too. What happened?
Dick: Runs and dizziness.
Zoe: Exactly the same for me.
Dick: You know, the same thing happened to me last week.
Zoe: It must be the food at the school cafeteria that's making us sick.
16. Suzy: You're mean.
Tom: What? Why do you say that?
Suzy: Because you're not nice.
17. What do you want to eat for dinner? Well, we had fish yesterday and pasta the other
day. We haven't eaten chicken for a while. How about some chicken with potatoes?
18. Maria: Almost all the professors I've met at this school are liberals.
Manuel: So to get a teaching job here it must help to be a liberal.
19. Tom: If Dick bought a new car, then he must have had more money than I thought.
Harry: Well, look, there's the new hatchback he bought.
Tom: So Dick must have had more money than I thought.
20. Zoe: Spot got out of the yard somehow.
Dick: He must have got out under the fence.
Zoe: No way he got out under the fence. There's no sign of new digging.
21. Zoe: Spot got out of the yard somehow.
Dick: He must have got out under the fence.
Zoe: No way he got out under the fence. There's no sign of new digging. And we
blocked all the old ways he used to get out under the fence.
22. Zoe: Spot got out of the yard somehow.
Dick: He must have got out under the fence.
Zoe: No way he got out under the fence. There's no sign of new digging. And we
blocked all the old ways he used to get out under the fence.
Dick: But he pulled down that chicken wire last week.
Zoe: {later) I checked—all the wire and rocks we put up are still there, and there's
no sign that the fence has been disturbed at the bottom.
Dick: I hope he hasn't learned how to jump over the fence.
23. Suzy: Every student who has ever taken a course from Professor Zzzyzzx has passed.
So if I take his composition course, I'll pass, too.
24. Tom: See that guy over there? He's a Muslim.
Suzy: And he has a beard. He must be a terrorist.
25. There are 30 seconds left in the football game. The 49ers have 35 points. The Dolphins
have 7 points. So the 49ers will win.
Writing Lesson 3
We've been learning how to analyze arguments. Now it's time to try to write one.
You know what tests a good argument must pass. It must be composed of
claims, and claims only. It shouldn't contain any ambiguous or excessively vague
sentences. It must be valid or strong. And the premises should be plausible, more
plausible than the conclusion.
Write an argument in OUTLINE FORM either for or against the following:
Everyone should use a bicycle as his or her main form of transportation.
• Just list the premises and the conclusion. Nothing more.
• Your argument shoul
d be at most one page long.
• Check whether your instructor has chosen a different topic for
this assignment.
It doesn't matter if you never thought about the subject or whether you think
it's terribly important. This is an exercise, a chance for you to sharpen your skills in
writing arguments. It's the process of writing an argument that should be your focus.
If you have trouble coming up with an argument, think how you would respond
if you heard someone say the claim at a city council meeting or if someone in class
said it. Make two lists: pro and con. Then write the strongest argument you can.
And in this case, remember to make clear what standards you're invoking for that
"should."
Don't get carried away. You're not expected to spin a one-page argument into
three pages. You can't use any of the literary devices that you've been taught are
good fillers. List the premises and conclusion—that's all. And remember, premises
and conclusion don't have those words "therefore" or "I think" attached. Once you can write an argument in this outline form, you can worry about making your
arguments sound pretty. It's clarity we want first.
To give you a better idea of what you're expected to do, below I've included
Tom's argument on a different topic.
53
54 Writing Lesson 3
Tom Wyzyczy
Critical Thinking
Section 4
Writing Lesson 3
Issue: Students should be required to take a course on critical thinking.
Definition: I'll understand the issue as "College students should be required to
take a course on critical thinking before graduating."
Premises:
1. A critical thinking course will help students to write better in their other
courses.
2. A critical thinking course will help students to read assignments in all their
other courses.
3. A critical thinking course will make students become better informed voters.
4. Most students who take a critical thinking course appreciate it.
5. Professors will be able to teach their subjects better if they can assume their
students know how to reason.
6. Critical thinking is a basic skill and should be required, like Freshman
Composition.
Conclusion: College students should be required to take a course on critical
thinking before graduating.
Tom, it's good that you began by making the issue precise. 'Even better is that you
realized the definition wasn't a premise. You've Learned a Lot from the Last assignment.