for genius2013

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© C. Jacob Hale, 2007

CHAPTER TWO
ARGUMENT EVALUATION:

THE BASIC CONCEPTS
Introduction to Evaluating Arguments

Once we have identified an argument and its parts, the next step is to evaluate the argument.
Noticing a use of ‘because’ different from those we studied in Chapter One will lead us into the
basic concepts used to evaluate arguments.

Let’s consider the following quotation from Britney Spears:

Just because I look sexy on the cover of Rolling Stone doesn’t mean I’m naughty.
[Britney Spears, “Britney Spears Quotes”;
http://www.brainyquote.com/quotes/authors/b/britney_spears.html.]

Although the word ‘because’ is introducing a premise here, something more complicated is going
on. The sentence construction

just because ______ doesn’t mean ______

is telling you that a particular argument is a bad argument, and that it is bad in particular way.
The word ‘because’ introduces the premise of the argument you’re being told is bad, and the
phrase ‘doesn’t mean’ introduces the conclusion of the argument you’re being told is bad.

Here is a reconstruction of the argument Spears is telling us is a bad argument:

(1) I look sexy on the cover of Rolling Stone.
____________________________________
(2) I’m naughty.

What kind of criticism does the ‘just because ______ doesn’t mean ______’ sentence construction
indicate? It indicates that even if the premise is true, it is not a reason to believe the conclusion.

Applying this to the Britney Spears example, she used the ‘just because ______ doesn’t mean
______’ sentence construction to indicate that even if it’s true that she looks sexy on the cover of
Rolling Stone, that is not a reason to believe she’s naughty.

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In this particular example, it might be more natural to understand Spears as saying that even
though – instead of ‘if’ – she looks sexy on the cover of Rolling Stone, that is not a reason to
believe she’s naughty. In other words, Spears seems to think that the premise is true. Sometimes,
however, the ‘just because ______ doesn’t mean ______’ sentence construction is used more
hypothetically, in ways to fit better with ‘even if’ than with ‘even though’. Consider this example:

Just because you’re 40 doesn’t mean you need to look 40. [“How to Look Great at
Any Age,” GQ (September 2005), p. 421.]

This sentence is telling you that the argument

(1) You’re 40.
______________________
(2) You’re need to look 40.

is a bad argument in the following way: even if (1) is true, this premise does not justify accepting
(2): even if it’s true that you’re 40, this is not a reason to believe you need to look 40.

Let’s consider one more example, which will perhaps make this point more clearly. In this
example, former basketball star Charles Barkely spoke about racism against African Americans:

People want to assume that just because you have money racism doesn’t affect
you, and that’s not really true. [Charles Barkely, quoted in “Sir Charles Talks
Frankly about Race,” Arizona Republic, April 24, 2005.]

Although Barkely did not use the ‘just because ______ doesn’t mean ______’ sentence
construction, it is easy to reword his point, as follows:

Just because an African American has money doesn’t mean racism doesn’t affect
that person.

Barkely does not deny that some African Americans have money; indeed, he’s made a lot of
money himself in the NBA and as a basketball commentator. What he does deny is that the
following argument is one in which the truth of the premise would be a reason to believe the
conclusion:

(1) An African American has money.
________________________________
(2) Racism does not affect that person.

When we are evaluating an argument, we must always two questions: first, are the premises all
true; and, second, if the premises are all true, are they really reasons to believe the conclusion?
Here are a couple of other ways to put the second question: If the premises are all true, do they
support the conclusion? If the premises are all true, do they justify accepting the conclusion?

The ‘just because ______ doesn’t mean ______’ sentence construction indicates that the answer
to the second question is “no.” (We’ll learn more about these two kinds of questions very soon.)

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PRACTICE PROBLEMS SET 2-1:
JUST BECAUSE ______ DOESN’T MEAN ______

Instructions: For each passage, reconstruct the argument that the ‘just because _____ doesn’t
mean _____’ sentence construction, or a similar construction, is telling you is a bad argument.
Do not add any ellipses.

Sample Problem:

Original Passage:

Just because it’s on the street doesn’t mean it’s not a great piece of furniture. [Ron
Marvin, “Small Space, Big Style,” HGTV, January 25, 2007.]

Answer:

(1) A piece of furniture is on the street.
________________________________

(2) It’s not a great piece of furniture.

1. …[J]ust because one skater paints graffiti on a building doesn’t mean they’re all criminals.
[Anthony Avery, quoted in Brent D. Wistrom, “Skaters Won’t Have to Skirt Law, Wichita
Eagle (Kansas), August 15, 2005.] 

2. Just because I slept with you doesn’t mean I’ll ski with you. [Whistler Blackcomb ski resort T-
shirt slogan.]

3. Just ’cause you change a man’s surroundings doesn’t mean that you change the man. [50 Cent
(Curtis James Jackson III) with Kris Ex, From Pieces to Weight: Once Upon a Time in
Southside Queens. (New York: Pocket Books/MTV Books, 2005), p. 219.]

4. …[M]erely because you profess Christianity doesn’t mean you have found an exclusive
avenue to the truth. [Donald Kaul, “Christianity Has Struck a Bumpy Patch,” Northeast Sun
(Los Angeles), April 20, 2006.] 

5. …[J]ust because the only Valentine’s Day gift I’ll be receiving this year is from my
mom, it doesn’t mean I’m a loser. [Caitlin White, “Just Say No to Valentine’s Day,” Orion
(California State University, Chico), February 14, 2007.]

6. If a person is infected with HIV it doesn’t mean that they have AIDS. [Roger Obakrairur,
Brenda Delisle and John Dax Moreno, “HIV/AIDS Survey Underway in NMI,” Saipan
Tribune (Micronesia), November 1, 2006.] 

7. Just because you read it in a magazine
Or see it on the tv screen
Doesn’t make it factual, actual.
[Michael Jackson, James Harris III, and Terry Lewis, “Tabloid Junkie;”
http://www.lyricsfreak.com/m/michael-jackson/92722.html.]

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8. Because a guy can bury a twenty-foot jumper or glide to the hoop like an angel doesn’t make
him the one to tell you how to live. [Kareem Abdul-Jabbar and Peter Knobler, Giant Steps.
(New York: Bantam Books, 1983), pp. 292-293.] 

9. Note: The phrase ‘fellow traveler’ means a person who, while not actually a Communist,
supports or sympathizes with Communists. This phrase was commonly used in the U.S. during
the middle part of the 20th century.

…[O]ccasional concurrence with the Communist party line does not necessarily mean that a
man is a Communist or a fellow traveler. [Simon H. Rifkind, quoted in “Leftists Sometimes
Used Him, Winchell Admits,” Los Angeles Times, June 30, 1953.]

10. …[T]he Supreme Court has ruled that a governor cannot block a National Guard deployment
just because he doesn’t like the purpose…. [“A Wide CampaignTrail,” Los Angeles Times,
September 30, 2006.] 

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What Kind of Criticism Is Raised?

An argument is a good argument – one in which the premises are reasons to believe the
conclusion, or provide support or justification for the conclusion – just in case it meets two
different conditions:

(1) its premises are all true, and

(2) its premises, assuming they are true,

support the conclusion.

That’s why when we’re evaluating an argument we ask two different kinds of questions:

(1) Are the premises all true?

(2) Assuming the premises are all true, do they support the conclusion?

It’s important to see that these are very different kinds of questions. The first question is about
whether what the premises say corresponds with the way the world is. The second question is
about the relationship between the premises and the conclusion. So, the first question is a factual
question but the second question is a logical question. (That doesn’t mean that the first question
is illogical; the first question is extralogical, that is, it is about something other than logic.)

Let me illustrate this difference with a couple of simple “made up” examples. First, consider the
following argument:

(1) Dixie is a snake.
___________________
(2) Dixie is a reptile.

This is a bad argument – that is, an argument in which the premise isn’t a reason to believe the
conclusion – because its premise is false: Dixie isn’t a snake, she’s a cat. Look back at the two
questions we must ask when evaluate an answer; about this argument, “no” is the answer to
question (1).

By contrast, let’s consider the following argument:

(1) Dervish weighs 11 pounds.
_________________________
(2) Dervish is a reptile.

This is a bad argument – that is, an argument in which the premise doesn’t support the conclusion
– because even if we assume that the premise is true it doesn’t support the conclusion.

All of the ‘just because ______ doesn’t mean ______’ (and similar) examples we went through
were criticizing an argument on the grounds that the answer to question (2) was “no.”

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Let me illustrate the difference again in a different way, by giving you some examples in which
an argument is presented and criticized.

Let’s the consider the following example, in which Jonah Goldberg presents and then criticizes
an argument:

…[A] claim [made by opponents of closed-circuit security cameras in public
areas] is that cameras won’t prevent attacks. Well, who says? Doesn’t it
become slightly more problematic for a terrorist cell to send one of its
stooges to his death if his face can be traced back to the mosque from
which he came? Isn’t it possible that cameras, combined with other
intelligence, may alert authorities that an area’s being cased before the
actual attack? [Jonah Goldberg, “Excuses, Excuses: Privacy in Public Is a Weak
Argument,” Tallahassee Democrat (Florida), August 2, 2005.]

Here is a reconstruction of the argument given by opponents of closed-circuit security cameras in
public areas, as Goldberg presents their argument in his first sentence:

(1) Closed-circuit security cameras in public areas won’t prevent terrorist attacks.
_________________________________________________________________

(2) We shouldn’t have closed-circuit security cameras in public areas.

Goldberg does not say anything about the logic of the argument, that is, about whether the
premise, if it were true, would be a reason to believe the conclusion. Instead, he uses two
rhetorical questions to challenge the truth of (1).

By contrast, let’s consider this example, in which Flip Kobler presents an argument and then
disagrees with it:

The apologists [for the Bush administration] keep sinking to new lows. So abuse
of detainees is the exception, not the rule. Well, heck, then it’s all OK.

That logic is right up there with “Gee, your honor, there were more days when I
didn’t kill people than days I did. So what’s the big deal?” [Flip Kobler, Letter to
the Editor, Los Angeles Times, June 21, 2006.]

Here is a reconstruction of the argument Kobler presents:

(1) Abuse of detainees is the exception, not the rule.
__________________________________________
(2) Abuse of detainees is OK.

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Kobler, unlike Goldberg, says nothing to challenge the truth of the argument’s premise. Instead,
he focuses on the argument’s logic, and he uses an analogy to do so, asking us to imagine a
murder defendant who argues to the trial judge as follows:

(1) There were more days when I didn’t kill people than days I did.
______________________________________________________
(2) The murder I committed is no big deal.

Kobler trusts his readers to see the absurdity of the reasoning in this analogous argument. His
criticism of both arguments is the same: even if the arguments’ premises are true, they aren’t
reasons to believe the arguments’ conclusions.

Let’s consider another example in which this kind of criticism is raised:

The suggestion that companies and individuals should be allowed secretly to
donate up to $10,000 to political parties is unacceptable.

Liberal Party federal director Brian Loughnane argues that inflation has changed
the real value of today’s $1500 limit.

This is a weak argument: what’s needed in politics is transparency.

Any increase in the level of covert payments is a step backwards, contravening
the crucial principle of transparency.

Disclosure is meant to ensure that politicians of any persuasion are not tempted to
serve the interests of people who give money to their party.

Mr Loughnane has failed to demonstrate that reducing transparency would be in
the public interest.

Until he does, his proposal carries no weight.
[“Islam and the Real World,” Melbourne Herald Sun (Australia), August 10,
2005.]

The argument of Loughnane’s presented by the author is the following:

(1) Inflation has changed the real value of today’s $1500 limit on secret donations
to political parties.

_________________________________________________________________
_

(2) Companies and individuals should be allowed secretly to donate up to $10,000
to political parties.

Nowhere does the author challenge the truth of (1). Instead, the author argues that (1) misses the
important point that what’s important in politics is transparency, and states that any increase in
the limit on secret donations to political parties contravenes – goes contrary to – the crucial
principle of transparency in politics. So, the author criticizes Loughnane’s argument on the
grounds that the premise, assuming it is true, does not justify accepting the conclusion.

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PRACTICE PROBLEMS SET 2-2:
WHAT KIND OF CRITICISM IS RAISED?

Instructions: Each passage in this practice problems set criticizes an argument on one of two
grounds: either the author of the passage claims that (a) the argument contains one or more
false premises or (b) the premise or premises, assuming they are true, do not support the
conclusion. For each passage, first reconstruct the argument that is criticized and, second,
identify the kind of criticism raised. For any arguments that are criticized on ground (a) and
contain more than one premise, say which premise the author claims is false. Do not add any
ellipses.

Sample Problems:

Original Passage:

Edward Gonzalez correctly states that Cubans have endured a highly repressive
totalitarian state under Castro (Current, Aug. 13). … In defense of Castro, some
refer to Cuba’s acclaimed public health benefits. But if that validates Castro’s
government, slavery would then be justified if the slaves received similar benefits.
[John F. Haggerty, Letter to the Editor, Los Angeles Times, August 19, 2006.]

Answer:

(1) Cuba has acclaimed public health benefits.
_____________________________________
(2) Castro’s government is valid.

Haggerty criticizes the argument on the ground that the premise, assuming it is
true, does

not support the conclusion.

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Original Passage:

The standard argument against a system that rewards good teachers and removes
bad teachers is that there is no fair or accurate way to tell good from bad. While
there may be no valid rubric to measure teacher quality, does anyone really think
that we do not already know good teachers and bad teachers? Just about anyone
can walk into any school and in a short time figure that out. Ask the other
teachers, students and parents. Observe the teacher. Are students inspired? Are
expectations high? Is the quality of student work high? Are people having fun?
[Dylan Hydes, “Education’s Needs: Fostering Active Parents, Better Teachers,”
San Jose Mercury News, June 29, 2005.]

Answer:

(1) There is no fair or accurate way to tell good teachers from bad teachers.
_________________________________________________________________
(2) We should not have a system system that rewards good teachers and removes

bad teachers.

Hydes criticizes the argument on the ground that its premise is false.

1. Just because I don’t have a boyfriend doesn’t mean I’m unhappy…. [Caitlin White, “Just Say
No to Valentine’s Day,” Orion (California State University, Chico), February 14, 2007.]

2. …[S]imply because a minor commits an act we think only an adults [sic] is capable of, this
doesn’t necessarily mean a minor has the mental capacity of an adult. To argue by analogy, a
minor is physically able to sign a contract. Simply because the contract is signed does not
mean the minor has mental capacity enough to be held responsible for his agreement. [Jes
Bohn, “Trying Minors in Court as Adults Unfair, Inconsistent,” Daily Sundial (California
State University, Northridge), April 21, 2005.] 

3. Note: A syllogism is a kind of argument we will study in Chapter Three.

The syllogism sounds perfect. You cannot open what is not closed. The South Coastal Road
was never closed. Ergo, the court cannot open it. For indeed, how can you open what has
never been closed?

But it only sounds perfect. In reality Cebu City Mayor Tomas Osmeña’s syllogism is full of
holes. We can certainly agree with the premise that you cannot open what is not closed.
However, we have to take exception to the … premise that the South Coastal Road was never
closed. Yes, it was open to a few motorists with passes. No, it was not open to the general
public like a public road should be. Ergo, the court was right to order it opened. The court’s
decision proved that, contrary to the mayor’s claim, the South Coastal Road, a government
project, was closed to the general public. [Orlando P. Carvajal, “Carvajal: Simply Amazing,
Absolutely Frustrating,” Sun Star (Philippines), October 26, 2005.]

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4. I got a kick out of the property owners’ side of the rent-control debate. Rent control gives
renters an unfair break “when they can easily afford more”? Rubbish! Wages haven’t kept up
with inflation for years and yet – as supporters of this argument eagerly point out – no law
keeps anything else we must buy or finance from increasing.

Housing is one of the basic necessities a human needs to stay alive and healthy. Rent control
is a legislative tool aimed at decreasing the likelihood of one becoming homeless due to greed
or market forces beyond their control. [Chris McManigal, Letter to the Editor, Real Estate
Section, Los Angeles Times, February 4, 2007.] 

5. Note: “Deep Throat” was the pseudonym of an anonymous informant who helped Washington
Post reporters Bob Woodward and Carl Bernstein document and expose the Watergate
scandal that brought down Richard M. Nixon’s presidency. Deep Throat’s identity was a
mystery until 2005, when it was revealed that W. Mark Felt was “Deep Throat.”

[John] Dean opened his 150-page e-book [Unmasking Deep Throat] with a quote from Sir
Arthur Conan Doyle, creator of Sherlock Holmes, that after excluding the impossible,
“whatever remains, however improbable, must be the truth.” He closed with another Conan
Doyle quote about the importance and prominence of data. “It is a capital mistake to theorize
before one has data. Insensibly, one begins to twist facts to suit theories, instead of theories to
suit facts.” Dean concludes his book, “With that thought in mind, I’ve little doubt the first
person to complete sorting through the facts will have everyone saying – why didn’t I think of
that?”

Dean made the sort of mistake that Arthur Conan Doyle warned of. He theorized that because
Deep Throat knew the Nixon White House, he must have actually worked within the Nixon
White House. After all, Dean’s own formative experience was at the Nixon White House. He
never could get around that. Like many people who worked in the White Houses of numerous
administrations, Dean could not appreciate that an outsider could see, know and piece
together its true nature. Those who are in the orbit, but nonetheless on its edges, can often be
the real discoverers. It is why at times, the journalist, the historian and even the novelist paints
the fullest picture of an era. [Bob Woodward, The Secret Man: The Story of Watergate’s Deep
Throat. (New York: Simon & Schuster, 2005), pp. 206-207.] 

6. Many critics [of displaying the Ten Commandments in public schools and courthouses] have
argued that the sight of the Ten Commandments may offend people of other religions, but
that’s an extremely weak argument. (I’m usually offended whenever I watch TV on the public
airwaves!) People who enter the courthouse do not have to acknowledge or respect the Ten
Commandments. [Jill S. Farrell, “Supreme Court: Ten Commandments in the Public Square,”
National Ledger (Arizona), August 7, 2005.]

7. Well, I’d like to say first that I think it’s a fairly weak argument to say … [CNN] didn’t [have a
responsibility to] cover the anti-war movement because it had no strong Democratic Party
spokesperson…. In fact, the anti-war movement was well organized as early as September
and was having demonstrations that were drawing hundreds of thousands. [Steve Rendall, a
senior analyst at Fairness and Accuracy In Reporting (FAIR), on Pacifica Radio’s
“Democracy Now!,” April 4, 2003.] 

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8. Note: In this passage, focus on the criticism presented by Los Angeles Unified School District
Superintendent Roy Romer against Los Angeles Mayor Antonio Villaraigosa’s argument.

On his second day in Sacramento trying to convince lawmakers to back his takeover of [Los
Angeles Unified School District] public schools, Los Angeles Mayor Antonio Villaraigosa
cited a new report that paints a bleak picture of graduation rates in the district.

The study, conducted by the research arm of the publication Education Week, concluded that
only about 44% of students in Los Angeles Unified School District graduate from high school
in four years. Of the country’s 50 largest public school districts, only five placed lower than
Los Angeles, the study found.

The report – and the mayor’s use of it to bolster his case – drew quick ire from top school
district officials, who rejected the study’s findings as inaccurate and outdated.

“The first thing that people in this town need to know,” is that the mayor’s program “is being
sold on false information,” said Supt. Roy Romer. “It’s a terrible way to treat people, to give
them false information. The mayor should know better.” [Joel Rubin, “Mayor Cites Dropout
Data to Push Plan,” Los Angeles Times, June 21, 2006.]

9. [An] argument in which bad faith parades as good faith is one which tries to justify
discrimination against gay teachers. It runs as follows: though openly gay teachers do not
cause their students to become gay, an openly gay teacher might (inadvertently or not) cause a
closeted gay student to become openly gay; the life of an openly gay person is a life of misery
or suffering; therefore, openly gay teachers must be fired, since they promote misery and
suffering. It seems that the second premise – life of misery – if true in some way peculiar to
gays, is so in the main as the result of currently existing bigotry and discrimination in society
of the very sort which the argument tries to enshrine into school board policy. [Richard D.
Mohr, A More Perfect Union: Why Straight America Must Stand Up for Gay Rights. (Boston:
Beacon Press, 1994), p. 94.] 

10. The PETA [People for the Ethical Treatment of Animals] folks maintain that fish feel pain
when they’re hooked and therefore the $116 billion per year fishing industry should
immediately shut down. Which makes about [as] much sense as shutting down the
automobile industry because driving cars has been known to kill deer, or, closer to home,
shutting down newspapers because we kill too many trees. …

Even if fish feel pain when hooked, which hasn’t been conclusively proven, so what … they’re
fish. No one’s crying for that mosquito that I smashed on my arm yesterday. [Jimmy Watson,
“PETA Pulls Ridiculous Ploy During Bassmaster Classic,” Shreveport Times (Louisiana),
August 7, 2005.]

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The Criteria for a Good Argument

Let’s review the two conditions an argument must meet to be a good argument:

(1) its premises are all true, and
(2) its premises, assuming they are true, support the conclusion.

What does the second condition mean? Clearly, it is vague, so I need to make it more precise,
which I begin to will do by defining a valid argument. A valid argument is one that has this
characteristic: assuming that the premises are all true, it is impossible for the conclusion to be
false. The opposite of a valid argument is an invalid argument. To define invalid argument, we
need to make only one change to the definition of valid argument: remove the prefix ‘im-‘ from
the word ‘impossible.’ So an invalid argument is an argument that has this characteristic:
assuming that the premises are all true, it is possible for the conclusion to be false. (Sometimes
we speak of the validity or invalidity of arguments, or say that a person was reasoning validly or
invalidly.) Validity and invalidity are determined by an argument’s form (or structure or pattern),
not its content.

Consider the following example:

(1) All cats meow.
(2) Lassie is a cat.
____________________
(3) Lassie meows.

Not all of this argument’s premises are true, of course, because premise (2) is false: Lassie is a
famous TV dog. So this is not a good argument: the premises do not support the conclusion. But
let’s assume for moment – grant for the sake of discussion or argument, if you like – that both
premises were true. If they were both true, then the conclusion would have to be true too. This
argument is valid.

This example is meant to show you two things. First, it is meant to show you that the second
condition an argument has to meet to be a good argument is very different than the first
condition. The second condition has to do with the logical relationship between premises and
conclusion. This is a matter of the form (or structure or pattern) of the argument. The first
condition is a matter of the argument’s content. Second, this example is meant that show that you
an argument can be valid without having all true premises.

Consider this example, as an illustration of an invalid argument:

(1) U.S. presidents are required by the Constitution to have been born in the
United States.

(2) Jacob Hale’s maternal grandfather was born in the U.S.
_________________________________________________________________
_
(3) Jacob Hale’s maternal grandfather is the current president of the United States.

141

Do you know the truth values of all of the premises in this argument? Probably not, because you
probably don’t know where my maternal grandfather was born. Here’s how to approach the
question of whether this argument is valid or invalid. First, assume that the premises are true.
Second, ask whether, given that assumption, it would be possible for the conclusion to be false.
Of course this is possible! So, this argument is invalid.

Let’s consider another invalid argument, one in which the premises and the conclusion are all
true:

(1) All professional baseball players are professional athletes.
(2) Barry Bonds is a professional athlete.
__________________________________________________
(3) Barry Bonds is a professional baseball player.

Although we know that the conclusion is true, the premises in this argument do not give us
reasons to believe the conclusion: there are many kinds of professional athletes who aren’t in
baseball and the premises say nothing to rule out the possibility that Bonds is another kind of
professional athlete. For example, the premises leave it possible that Bonds is a pro basketball
player, golfer, ice skater, bicyclist, gymnast, tennis player, etc. This argument is invalid.

A caution: the words ‘valid’ and ‘invalid’ are used in a number of ways in ordinary English, but
here we are using them with technical, precise meanings. If you are just “on the right track” in
your understanding of these concepts, that’s not good enough: you will not be able to apply them
correctly, if you’re just “on the right track.” So, you need to memorize and understand the precise
definitions of these terms.

DEFINITIONS OF ‘VALID ARGUMENT’
AND ‘INVALID’ ARGUMENT’:

VALID ARGUMENT = def An argument with this characteristic:
Assuming the premises are all true, it is impossible for the conclusion to be
false.

INVALID ARGUMENT = def An argument with this characteristic:
Assuming the premises are all true, it is possible for the conclusion to be false.

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The Relationship Between Validity and Truth

The definition of valid argument rules out only one combination of actual (not assumed, but
actual – real) truth values: all true premises and a false conclusion. Any such argument is, by
definition, invalid. However, any other combination of actual truth values is possible in a valid
argument, and an invalid argument can have any combination of actual truth values. The chart
below illustrates this, with reference to the specific examples that follow the charts.

IN

VALID ARGUMENTS

true premises and true conclusion:

Example 1

true premises and false conclusion:

Example 2

false premises and true conclusion:

Example 3

false premises and false conclusion:

Example 4

VALID ARGUMENTS
true premises and true conclusion:

Example 5

true premises and false conclusion:

impossible

false premises and true conclusion:

Example 6

false premises and false conclusion:

Example 7

THE EXAMPLES

Example 1: Invalid argument with all true premises and a true conclusion:
(Please take my word for it on the truth values in this example.)

(1) If I’ve won the MegaMillions jackpot, then I am wealthy.
(2) I haven’t won the MegaMillions jackpot.
_________________________________________________
(3) I am not wealthy.

Example 2: Invalid argument with all true premises and a false conclusion:

(1) Brad Pitt is a famous movie star.
(2) Angelina Jolie is a famous movie star.
__________________________________
(3) Brad Pitt is Angelina Jolie.

Example 3: Invalid argument with all false premises and a true conclusion:

(1) Los Angeles is a small town in the United States.
(2) New York City is a small town in the United States.
_____________________________________

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(3) New York City is larger than Los Angeles.

Example 4: Invalid argument with all false premises and a false conclusion:

(1) Abraham Lincoln is the current U.S. president.
(2) Dwight D. Eisenhower is the current U.S. president.
______________________________________________
(3) Abraham Lincoln is Dwight D. Eisenhower’s father.

Example 5: Valid argument with all true premises and a true conclusion:

(1) Every cat needs oxygen to survive.
(2) Dervish is a cat.
_______________________________
(3) Dervish needs oxygen to survive.

Example 6: Valid argument with all false premises and a true conclusion:

(1) Dixie is a bird.
(2) All birds are animals.
____________________
(3) Dixie is an animal.

Example 7: Valid argument with all false premises and a false conclusion:

(1) Gorshie is a bird.
(2) All birds are elephants.
______________________
(3) Gorshie is an elephant.

Examples 6 and 7 illustrate why an argument can be valid but still not good: in neither of these
two arguments do the premises justify accepting the conclusion. This is why the premises must
be true for an argument to be a good argument. Here is an additional definition: A sound
argument is one that meets both of these conditions: (1) it is valid, and (2) it has all true
premises. So, example #5 is the only one of the seven examples above that is sound. An
argument that fails to meet either (or both) of these two conditions is unsound.

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Here’s an analogy that might help you understand the definitions of validity and soundness.
Imagine that Aline wants to drive from Hollywood to San Jose to visit her aunt and uncle, and
because she is new to California, she doesn’t know the way to San Jose. So, she looks at a
California road map, which shows that if she gets onto the 101 freeway northbound she can drive
all the way to San Jose without having to get onto any other freeway or highway. Aline doesn’t
have any background information that lets her know that the map is accurate, but she assumes it
is and realizes that if the map is accurate, then she can take the 101 all the way from Hollywood
to San Jose. Aline’s situation is similar to validity in this respect: if the premises are all true then
the conclusion must be true, and if the map is accurate then Aline can take the 101 all the way
from Hollywood to San Jose.

Aline’s situation is also similar to argumentation in general in this respect: when an arguer gives
an argument s/he can be understood (at least, in most contexts) as asserting that her/his premises
are true and when a mapmaker makes a map s/he can be understood (at least, in most contexts)
as representing the map as accurate.

There is an important difference between Aline’s situation and the concept of soundness, which
is this: most printed road maps are accurate at the time they are published, or else they wouldn’t
be published, so Aline’s assumption about the map’s accuracy is probably justified, but it is a
much less safe bet for us to assume that most arguer’s premises are true. When evaluating an
argument for validity, we must assume that the premises are true. But when evaluating an
argument for the other criterion of soundness – that the premises are all true – we will not
assume that they are.

You might think of assuming that the premises are true while evaluating an argument for validity
as similar, in some respects, to suspending disbelief while watching Buffy the Vampire Slayer or
an old Dracula movie starring Bela Lugosi. Most people who enjoy TV shows or movies about
vampires don’t really believe that vampires exist. Instead, they suspend their disbelief while
watching a vampire TV show or movie. This suspension of disbelief occurs for a specific
purpose – being able to follow and enjoy the show – and for a limited period of time – while
watching the show. Similarly, while evaluating an argument for validity, we assume that the
premises are, but only for a specific purpose – being able to evaluate the argument for validity –
and only for a limited period of time – while evaluating the argument for validity.

Argument evaluation depends crucially on distinguishing between the two conditions for
soundness: validity and the truth of the premises. Consider the following excerpt from Abraham
Lincoln’s speech during his fifth debate with Stephen Douglas, his opponent in the 1858
presidential election. Lincoln told the audience why he disagreed with the U.S. Supreme Court’s
decision in the famous Dred Scott case, in which the Court had ruled that slaves who had

DEFINITIONS OF ‘SOUND ARGUMENT’
AND ‘UNSOUND’ ARGUMENT’:

SOUND ARGUMENT = def A valid argument with all true premises.

UNSOUND ARGUMENT = def An argument that is invalid or that has at
least one false premise (or both).

145

escaped to Northern states that didn’t recognize slavery had to be returned to their “owners” in
the South. (A syllogism is a kind of argument we will study in Chapter Three.) Lincoln said:

I submit to the consideration of men capable of arguing whether, as I state it, in
syllogistic form, the argument has any fault in it:

Nothing in the Constitution or laws of any State can destroy a right
distinctly and expressly affirmed in the Constitution of the United States.

The right of property in a slave is distinctly and expressly affirmed in the
Constitution of the United States.

Therefore, nothing in the Constitution or laws of any State can destroy
the right of property in a slave.

I believe that no fault can be pointed out in that argument; assuming the truth of
the premises, the conclusion, so far as I have capacity at all to understand it,
follows inevitably. There is a fault in it as I think, but the fault is not in the
reasoning; but the falsehood in fact is a fault of the premises. I believe that the
right of property in a slave is not distinctly and expressly affirmed in the
Constitution, and Judge Douglas thinks it is. I believe that the Supreme Court and
the advocates of that decision may search in vain for the place in the Constitution
where the right of property in a slave is distinctly and expressly affirmed. I say,
therefore, that I think one of the premises is not true in fact. [Abraham Lincoln,
1858, in Roy R. Basler, ed., The Collected Works of Abraham Lincoln, Vol. 3.
(New Brunswick, NJ: Rutgers University Press, 1953), p. 231.]

In this excerpt, Lincoln argued that the U.S. Supreme Court’s argument was unsound because,
although it was valid, it had a false premise. He further told his audience exactly which of the
Court’s premises he thought was false.

What if you don’t know whether all of an argument’s premises are true? Consider this example:

(1) All U.S. senators must be U.S. citizens.
(2) Jesse Helms was a U.S. senator from North Carolina.
______________________________________________
(3) Jesse Helms was a U.S. citizen.

Some of you might know the truth values of all of this argument’s premises, but I’m guessing that
most of you don’t – in particular, I’m guessing that most of you don’t know whether (2) is true or
false. Of course, you can tell that this argument is valid without knowing the truth values of its
premises, so you know that one of the conditions for soundness is met, but you don’t know
whether both of the conditions for soundness are met. So, you don’t know whether this argument
is sound or unsound.

In general, there are three options open to you when you are asked whether an argument is sound
or unsound. You might answer:

♦ “The argument is sound.”

♦ “The argument is unsound.”

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♦ “I don’t know.”

When asked about the example we just considered, I’m guessing that most of you would have to
answer that you don’t know. You could elaborate on this by saying

“I don’t know whether the argument is sound or unsound, because I don’t know
whether premise (2) is true or false (although I know the argument is valid).”

147

PRACTICE PROBLEMS SET 2-3:
ARE THE ARGUMENTS SOUND?

Instructions: For each argument in this practice problems set, say whether it is sound or
unsound. For any argument you say is unsound, say what makes it unsound.

Sample Problems:

Original Argument:

(1) Seoul is in South Korea.
(2) South Korea is in Asia.
_______________________
(3) Seoul is in Asia.

Answer:

Sound

Original Argument:

(1) All cars are trucks.
(2) All trucks are motorcycles.
_________________________
(3) All cars are motorcycles.

Answer:

Unsound, because premises (1) and (2) are both false

1. (1) All people drive cars.
(2) All zebras are people.
_____________________
(3) All zebras drive cars. 

2. (1) There are fifty states in the U.S.A.
(2) Each state in the U.S.A. has a governor.
______________________________________________
(3) Arnold Schwarzenegger is the governor of California.

3. (1) There are eighty-five states in the U.S.A.
(2) Each state in the U.S.A. is in Mexico.
____________________________________
(3) Canada is in Africa. 

148

4. (1) The country of France is in Texas.
(2) The country of Iran is in Nevada.
______________________________
(3) Los Angeles is in California.

5. (1) Every coffee shop serves coffee.
(2) Starbucks is a coffee shop.
_____________________________
(3) Starbucks serves coffee. 

6. (1) Harvard University is a university.
(2) All universities are in California.
________________________________
(3) Harvard University is in California.

7. (1) San Diego State University (SDSU) is a university.
(2) SDSU is in California.
____________________________________________
(3) All universities are in California. 

8. (1) The earth is a planet.
(2) Los Angeles is on the earth.
__________________________
(3) Los Angeles is on a planet.

9. (1) If you’re a professional baseball player, you are a professional athlete.
(2) Kobe Bryant isn’t a professional baseball player.
___________________________________________________________
(3) He’s not a professional athlete.

10. (1) All elephants can fly.
(2) All animals that can fly are mammals.
_________________________________
(3) All elephants are mammals.

11. (1) All cats have gray fur.
(2) All ginger-colored cats are cats.
___________________________________
(3) All ginger-colored cats have gray fur. 

12. (1) If you’re a college athlete, you do not get paid to play sports.
(2) If you do not get paid to play sports, you play sports for free.
____________________________________________________
(3) If you’re a college athlete, you play sports for free.

149

13. (1) If Gorshie is a cat, he’s a mammal.
(2) Gorshie is a cat.
_______________________________
(3) Gorshie is a mammal. 

14. (1) If Gorshie is a cat, he’s a mammal.
(2) Gorshie isn’t a cat.
_______________________________
(3) Gorshie isn’t a mammal. 

15. (1) All brown-haired people have green eyes.
(2) All people who have green eyes are college presidents.
_______________________________________________
(3) All brown-haired people are college presidents.

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The Method of Counterexample: A Way to Demonstrate Invalidity

Let’s remember whether an argument is valid or invalid is determined by the argument’s form (or
structure or pattern), not by its content. Also, let’s recall that for an argument to be invalid means
that it has the following characteristic: assuming that all its premises are true, it is possible for its
conclusion to be false. So, one way to demonstrate the invalidity of a specific argument is by
making up an example of an argument that has the same form and that has all true premises and a
false conclusion.

Let me illustrate this by considering the following example:

(1) If I have wings, then I can fly.
(2) I do not have wings.
____________________________
(3) I cannot fly.

This argument is an instance (or example) of a particular argument form, so a way to
demonstrate that this argument is invalid is to make up another instance of the same form such
that the instance we make up has all true premises and a false conclusion. Such an instance is a
called a counterexample. For a counterexample to be effective, both the person who gives it and
that person to whom it is given must share the knowledge that the counterexample’s premises are
all true and that the counterexample’s conclusion is false. So, it’s not enough for the
counterexample to have all true premises and a false conclusion; its premises must be well-
known truths and its conclusion must be a well-known falsehood.

There are many counterexamples to this argument form, but here is one:

(1) If elephants are dogs, then they are mammals.
(2) Elephants aren’t dogs.
_______________________________________
(3) Elephants aren’t mammals.

This counterexample demonstrates the invalidity of the argument form of which it is an instance,
so it demonstrates the invalidity of every instance of that argument form.

151

Let’s consider another example:

(1) All mammals are warm-blooded.
(2) My neighbor’s pet is warm-blooded.
________________________________
(3) My neighbor’s pet is a mammal.

Again, to demonstrate that this argument is invalid, we need to make up a counterexample that
has all three of the following characteristics:

♦ our counterexample is an instance of the same argument form as the example
we started with

♦ our counterexample’s premises are all well-known truths

♦ our counterexample’s conclusion is a well-known falsehood

Here is a counterexample:

(1) All students in first grade are human beings.
(2) CBS News Anchor Katie Couric is a human being.
________________________________
(3) CBS News Anchor Katie Couric is a student in first grade.

152

PRACTICE PROBLEMS SET 2-4:
MAKING UP COUNTEREXAMPLES

Instructions: Each argument in this practice problems set is invalid. For each, make up a
counterexample. Your counterexample must (1) be of the same form as the original example, (2)
have premises that are all well-known truths, and (3) have a conclusion that is a well-known
falsehood. When you’re thinking about whether a truth or a falsehood is well known to be a truth
or a falsehood, ask yourself whether it’s reasonable to assume that all your classmates will share
the knowledge you have; keep in mind both the differences between majors and between cultures
that are represented in your class.

Sample Problems:

Argument:

(1) Some physicians are unhappy people.
(2) Some unhappy people are men.
____________________________________________________
(3) Some physicians are men.

Answer:

(1) Some mammals are animals that can swim.
(2) Some animals that can swim are fish.
____________________________________________________
(3) Some mammals are fish.

1. (1) All people drive cars.
(2) All people are zebras.
_______________________
(3) All zebras drive cars. 

2. (1) If Dervish is a cat, then he is a mammal.
(2) Dervish is a mammal.
___________________________________
(3) Dervish is a cat.

3. (1) Some A’s are easy to get.
(2) Some things that are easy to get aren’t worth getting.
_____________________________________________
(3) Some A’s aren’t worth getting. 

4. (1) If there continues to be a supply of illegal drugs, then the War on Drugs will fail.
(2) If there continues to be a demand for illegal drugs, then the War on Drugs will fail.
___________________________________________________________________________
(3) If there continues to be a demand for illegal drugs, then there will continue to be a supply

of illegal drugs.

5. (1) If there continues to be a demand for illegal drugs, then the War on Drugs will fail.
(2) If there continues to be a supply of illegal drugs, then there will continue to be a demand

for illegal drugs.
______________________________________________________________________
(3) If the War on Drugs fails, then there will continue to be a supply of illegal drugs. 

153

6. (1) Gorshie ate Fillet Meow or What’s the Catch? today.
(2) Gorshie ate What’s the Catch? today.
____________________________________________
(3) Gorshie did not eat Fillet Meow today.

7. (1) No monkeys are chimpanzees.
(2) Some chimpanzees are happy animals.
__________________________________
(3) Some monkeys are not happy animals. 

8. (1) All dogs are mammals.
(2) All mammals are warm-blooded animals.
____________________________________
(3) Some warm-blooded animals are dogs.

9. (1) All Peruvians are South Americans.
(2) No Peruvians are people who can live without oxygen.
_______________________________________________________
(3) No South Americans are people who can live without oxygen. 

10. (1) No college students are lions.
(2) No lions are insects.
____________________________
(3) No college students are insects.

154

The Distinction Between Deductive and Inductive Arguments

Not all arguments are intended to be valid and have all true premises; that is, not all arguments
are intended to be sound. Sometimes arguers sincerely intend for their arguments to be good, but
they are trying to reach a “standard of proof” lower than validity. Consider this example:

(1) My cats were inside all day today.
(2) When they’re inside all day, they’re usually wild in the evening.
______________________________________________________
(3) My cats will be wild this evening.

This argument is invalid, because the premises leave open the possibility that today is an unusual
day, so even assuming (1) and (2) are true, (3) might be false. But if we understand this argument
as trying to meet a “standard of proof” lower than validity, it might be still be a good argument.

Consider, also, the following example:

[Rubén] Vizcaíno [is] … a cantankerous man in his seventies who, judging by his
short, fat tie, yellowed shirt and suspenders, probably hasn’t bought a new suit
since the fifties…. [Rubén Martínez, The Other Side: Fault Lines, Guerilla Saints,
and the True Heart of Rock ‘n’ Roll. (London: Verso, 1992), p. 90.]

Here, Martínez’s conclusion

Rubén Vizcaíno hasn’t bought a new suit since the fifties

is prefaced by the word ‘probably’. This tells us that Martínez doesn’t think his premise, assuming
it is true, provides absolutely certain proof of his conclusion. Rather, he thinks that if his premise
is true, his conclusion is probably true too. Martínez is not trying to give a valid argument – he is
trying to reach a lower “standard of proof.”

This is the key to the difference between deductive and inductive arguments. The basic idea
underlying the distinction has to do with the degree of support the premises, assuming they are
true, provide for the conclusion. A deductive argument, at its best (that is, just in case it is
sound), provides a guarantee that its conclusion is true. Inductive arguments, no matter how good
they are, never provide this guarantee. Rather, an inductive argument, at its very best, makes the
truth of its conclusion very likely but less than certain.

Let’s consider again the argument with the conclusion that my cats will be wild this evening:

(1) My cats were inside all day today.
(2) When they’re inside all day, they’re usually wild in the evening.
______________________________________________________
(3) My cats will be wild this evening.

155

Let’s assume that the premises are true. If they are, it is very likely that the conclusion is true, but
it is still possible for the conclusion to be false. This is an example of a strong inductive
argument. A strong argument is an argument that has the following characteristic: assuming
that the premises are all true, it is very unlikely that the conclusion is false. The opposite of a
strong argument is a weak argument. Just as a deductive argument can be valid but not have all
true premises (and, therefore, be unsound), an inductive argument can be strong but not have all
true premises. We will call an inductive argument that is strong and has all true premises a
compelling argument.

To illustrate more fully the point that a compelling argument can have a false conclusion (though
a sound argument cannot), consider the following example. (“Deep Throat” was the pseudonym
of an anonymous informant who helped Washington Post reporters Bob Woodward and Carl
Bernstein document and expose the Watergate scandal that brought down Richard M. Nixon’s
presidency. Deep Throat’s identity was a mystery until 2005, when it was revealed that W. Mark
Felt was “Deep Throat.”)

In June [of 1974], Washingtonian magazine published a story saying [W. Mark]
Felt was the most likely candidate to be Deep Throat, reasoning that he had
motive, opportunity, access, knew the methods for clandestine meetings and was
offended by Nixon and his men.

On June 25, The Wall Street Journal did one of their signature tongue-in-cheek
front page feature stories headlined: “If You Drink Scotch, Smoke, Read, Maybe
You’re Deep Throat.” It began, “W. Mark Felt says he isn’t now, nor has he ever
been Deep Throat. Of course, says the former acting associate director of the FBI,
if he really were Deep Throat, you’d hardly expect him to admit it, now would
you? Not that he is, Felt quickly adds.”

Felt told the Journal reporter that he didn’t disagree with the reasoning that it was
he. “But I do disagree with the conclusion. Because I’m just not that kind of
person.” I recall reading the quote. It left me cringing. Felt told that Journal he
thought that Deep Throat was a “composite.” He was the first person I know of to
float that theory – another false trail and superb cover for Deep Throat. [Bob
Woodward, The Secret Man: The Story of Watergate’s Deep Throat. (New York:
Simon & Schuster, 2005), pp. 116-117.]

In this example, that the Washingtonian’s argument was intended to be inductive is indicated by
the phrase ‘most likely’. This is reinforced by the response from Felt. Felt did not criticize the
Washingtonian’s argument by saying that it had one or more false premises. Nor did he criticize
the Washingtonian’s argument by saying that he disagreed with the reasoning – in fact, he said
didn’t disagree with the Washingtonian’s reasoning yet he still disagreed with the conclusion.
Felt’s comments only make sense if we:

156

(1) interpret the Washingtonian’s argument as a compelling inductive argument;

(2) understand Felt as recognizing the Washingtonian’s argument as a compelling
inductive argument; and,

(3) understand Felt as asserting that, even though the Washingtonian’s argument is
compelling, its conclusion is false.

157

CRUCIAL DEFINITIONS FOR CHAPTER TWO

DEDUCTIVE ARGUMENT = def. An argument that the arguer intends to be valid.
A good deductive argument is sound.

SOUND ARGUMENT = def A valid argument with all true premises. (Opposite:
unsound) Note: The term ‘sound’ is only applied to deductive arguments.

UNSOUND ARGUMENT = def An argument that is invalid or has at least one false
premise (or both). (Opposite: sound) Note: The term ‘unsound’ is only applied to deductive
arguments.

VALID ARGUMENT = def An argument with this characteristic:
Assuming the premises are all true, it is impossible for the conclusion to be false.
(Opposite: invalid) Note: The term ‘valid’ is only applied to deductive arguments.

INVALID ARGUMENT = def An argument with this characteristic:
Assuming the premises are all true, it is possible for the conclusion to be false. (Opposite:
valid) Note: The term ‘invalid’ is only applied to deductive arguments.

INDUCTIVE ARGUMENT = def. An argument that the arguer intends to be strong.
A good inductive argument is compelling.

COMPELLING ARGUMENT = def A strong argument with all true premises.
(Opposite: uncompelling) Note: The term ‘compelling’ is only applied to inductive
arguments.

UNCOMPELLING ARGUMENT = def An argument that is weak or has at least one
false premise (or both). (Opposite: compelling) Note: The term ‘uncompelling’ is only
applied to inductive arguments.

STRONG ARGUMENT = def An argument with this characteristic:
Assuming the premises are all true, it is very unlikely that the conclusion is false.
(Opposite: weak) Note: The term ‘strong’ is only applied to inductive arguments.

WEAK ARGUMENT = def An argument with this characteristic:
Assuming the premises are all true, it is not very unlikely that the conclusion is false.
(Opposite: strong) Note: The term ‘weak’ is only applied to inductive arguments.

158

Unstated Premises

In Chapter One, we saw that sometimes arguers leave their conclusions unstated. Similarly,
sometimes arguers leave a premise (or even more than one premise) unstated. In fact, in
everyday reasoning it is very common for a premise to be left unstated; it is much more common
for a premise to be left unstated than it is for all premises to be spelled out. But before we can
evaluate an argument, we need to know what all of its premises are. So, when we come across an
argument with an unstated premise, we will need to add that premise.

An unstated premise in a deductive argument is a premise that must be added for the
argument to be valid. By definition, then, every deductive argument with an unstated premise is
valid. Of course, that doesn’t mean that every deductive argument with an unstated premise is
sound. (Also, not every deductive argument with an unstated conclusion is valid.)

Consider the following example:

Dixie is a cat, so she’s a mammal.

Let’s begin by assuming that this argument is deductive. We can reconstruct (the stated parts of)
it as follows:

(1) Dixie is a cat.
_________________
(2) She’s a mammal.

Clearly, this argument is invalid as it stands, because no connection at all has been made between
being a cat and being a mammal; so assuming that (1) is true it is possible for (2) to be false. But
we can easily make this argument valid by adding a premise that makes the right kind of
connection between (1) and (2). The right kind of connection is one that excludes the possibility
that the conclusion is false, given the assumption that the premises – both the stated premise and
the unstated premise we will add – are true. We can state this connection as follows:

All cats are mammals.

Putting all of this together, we can understand the original argument as a valid deductive
argument with an unstated premise, as follows:

(1) Dixie is a cat.
(2) All mammals are cats. (unstated)
_________________
(3) She’s a mammal.

159

An unstated premise in an inductive argument is a premise that must be added for the
argument to be strong. By definition, then, every inductive argument with an unstated premise is
strong. But that doesn’t mean that every inductive argument with an unstated premise is
compelling.

Let’s consider the following argument:

(1) Dervish is a cat.
__________________
(2) He likes tuna fish.

Again, no connection has been made between (1) and (2) – between being a cat and liking tuna
fish – so this argument is invalid and weak. Let’s consider this as an example of an inductive
argument, that is, an argument that is intended to be strong. To make the argument strong, we
can easily add the following premise:

Most cats like tuna fish.

Putting all of this together, we can understand the original argument as a strong inductive
argument with an unstated premise, as follows:

(1) Dervish is a cat.
(2) Most cats like tuna fish. (unstated)
_____________________
(3) He likes tuna fish.

Let’s consider another example, from a Muddy Waters’ song:

I don’t believe my woman love me.
She’s in love with another man.
[Muddy Waters, “Flood,” (1952) on Muddy Waters, The Chess Box – 1. (MCA
Records; CHD3-80002.]

We can reconstruct Muddy Waters’ argument as follows:

(1) My woman is in love with another man.
___________________________________
(2) My woman doesn’t love me.

What can we add to this argument to make it valid? The following premise will work:

No woman can be in love with two men at the same time. (unstated)

160

Putting all of this together, we can understand the original argument as a valid deductive
argument with an unstated premise, as follows:

(1) My woman is in love with another man.
(2) No woman can be in love with two men at the same time. (unstated)
________________________________________________
(3) My woman doesn’t love me.

Remember that valid arguments are not necessarily good ones – that is, not all valid arguments
are sound. Just as it is a legitimate criticism of an argument to point out that one of its stated
premises is false or very implausible, it is an equally legitimate criticism of an argument with an
unstated premise to point out that its unstated premise is false or very implausible. Based on my
experiences, I believe Muddy Waters’ unstated premise is false because I have known women
who certainly seemed to be in love with two men at the same time. So, I think his argument is a
valid argument with at least one false premise, therefore it is unsound (which, of course, doesn’t
decrease my enjoyment of his song).

So far I have been assuming that Muddy Waters’ argument is deductive; that is, I have been
assuming that he intended it to be valid. Maybe my assumption is false: maybe his argument is
inductive; that is, maybe he intended it to be strong but not valid. Understanding his argument as
inductive, we’ll add a different (and, I think, more plausible) unstated premise, as follows:

(1) My woman is in love with another man.
(2) Most women can’t be in love with two men at the same time. (unstated)
___________________________________________________
(3) My woman doesn’t love me.

Here’s another example, which I will consider first as a deductive argument and then as an
inductive argument:

Because Gore Vidal is a famous person…, he has been interviewed hundreds of
times. [Robert J. Stanton, “Introduction,” in Robert J. Stanton, ed., Views From a
Window: Conversations with Gore Vidal. (Secaucus, N.J.: Lyle Stuart, 1980), p.
15.]

Here is a reconstruction of (the stated parts of) the argument:

(1) Gore Vidal is a famous person.
______________________________________
(2) He has been interviewed hundreds of times.

First, considering these as a deductive argument, we must add a premise that will make it valid.
We can do this in the following way:

(1) Gore Vidal is a famous person.
(2) All famous people have been interviewed hundreds of times. (unstated)
___________________________________________________
(3) He has been interviewed hundreds of times.

Next, let’s consider this argument as inductive. So now we must add a premise that will make it
strong, like this:

(1) Gore Vidal is a famous person.
(2) Most famous people have been interviewed hundreds of times. (unstated)

161

_____________________________________________________
(3) He has been interviewed hundreds of times.

I’m sure that by now you’ve noticed that a pattern in how I’ve been adding unstated premises.
When we’ve been assuming that the argument in question is deductive, I’ve added unstated
premises with quantity words that don’t allow any exceptions (such as ‘no’, ‘every’, and ‘all’). But
when we’ve been assuming that the argument in question is inductive I’ve been adding unstated
premises with quantity words that do allow for exceptions (such as ‘most’). This is a good
strategy to keep in mind.

I’ll illustrate another strategy that is sometimes useful by reference to an example from the Los
Angeles Times’ report on a study published in Science on February 16, 2007, which gave
evidence that chile peppers were domesticated by agricultural societies in the Americas more
than 6,000 years ago:

Chiles are rich in vitamin C, so ancient people who ate them would have gained a
nutritional advantage over those who didn’t, said Scott Raymond, a University of
Calgary archeologist and coauthor of the study. [Karen Kaplan, “Chiles’ Kick Is
an Old Story, Scientists Find,” Los Angeles Times, February 16, 2007.]

Here is a reconstruction of Raymond’s argument:

(1) Chiles are rich in vitamin C.
_________________________________________________________________
(2) Ancient people who ate them would have gained a nutritional advantage over

those who didn’t.

Let’s first understand Raymond’s argument as deductive. We can add an “if…then…” statement
as the unstated premise; we’ll need to put the stated premise after the word ‘if’ and we’ll need to
put the conclusion after the word ‘then’. Here’s what we get:

(1) Chiles are rich in vitamin C.
(2) If chiles are rich in vitamin C, then ancient people who ate them would have

gained a nutritional advantage over those who didn’t. (unstated)
_________________________________________________________________
_
(3) Ancient people who ate them would have gained a nutritional advantage over

those who didn’t.

By the way, this is a very common valid argument pattern, known as Modus Ponens; we’ll learn
more about it in Chapter Four.

162

Now let’s understand Raymond’s argument as inductive. We’ll need to add an unstated premise
leaves a slight possibility that the conclusion is false even assuming that the premises are true,
which we can do by modifying ever so slightly the unstated premise we already added when we
were understanding the argument as deductive. Doing so gives us the following:

(1) Chiles are rich in vitamin C.
(2) If chiles are rich in vitamin C, then ancient people who ate them probably

would have gained a nutritional advantage over those who didn’t. (unstated)
________________________________________________________________
(3) Ancient people who ate them would have gained a nutritional advantage over

those who didn’t.

As you work through practice problems, you’ll learn more strategies to use when adding unstated
premises.

163

PRACTICE PROBLEMS SET 2-5:
ADDING UNSTATED PREMISES

Instructions: For each problem, first reconstruct the argument including an unstated premise
that will make the argument valid. Second, reconstruct the argument including an unstated
premise that will make the argument strong. Label the unstated premise as such. Do not add any
ellipses.

Sample Problems:

Original Passage (with the argument boldfaced and underlined):

The smallest [East African carnivore] is the Dwarf Mongoose, Nguchiro or
Kicheche, which hunts in large packs for insects and small creatures by day,
making temporary homes in termite hills. This mongoose is easily tamed and
can be treated as a domestic pet. [Shell Guide to Wild Life. (Nairobi: Injes May,
1976), p. 22.]

Answer:

Reconstruction with an unstated premise that makes the argument valid:

(1) The Dwarf Mongoose is easily tamed.
(2) All animals that are easily tamed can be treated as domestic pets. (unstated)
_______________________________________________________

(3) The Dwarf Mongoose can be treated as a domestic pet.

Reconstruction with an unstated premise that makes the argument strong:

(1) The Dwarf Mongoose is easily tamed.
(2) Most animals that are easily tamed can be treated as domestic pets. (unstated)
________________________________________________________

(3) The Dwarf Mongoose can be treated as a domestic pet.

164

Original Passage:

I cannot go back to toys. I am grown expensive and sophisticated. [Ralph Waldo
Emerson, Essays: Second Series. (New York: Houghton Mifflin and Company,
1887), p. 167.]

Answer:
Reconstruction with an unstated premise that makes the argument valid:

(1) I am grown expensive and sophisticated.
(2) Nobody who has grown expensive and sophisticated can go back to toys.

(unstated)
______________________________________________________________

(3) I cannot go back to toys.

Reconstruction with an unstated premise that makes the argument strong:

(1) I am grown expensive and sophisticated.
(2) Most people who have grown expensive and sophisticated cannot go

back to toys. (unstated)
__________________________________________________________

(3) I cannot go back to toys.

1. As one of the world’s most beloved artists and incomparable live entertainers, Paul McCartney
will deliver an inspirational performance. [“Controversy? He’ll Let It Be,” Los Angeles Times,
November 22, 2004.] 

2. Because … [José Díaz] was born in Mexico, he was not subject to the draft [during World
War II]…. [Eduardo Obregón Pagán, Murder at the Sleepy Lagoon: Zoot Suits, Race, and
Riot in Wartime L.A. (Chapel Hill, North Carolina: The University of North Carolina Press,
2003), p. 1.]

3. [There is] … no need for setting apart one day in seven as a holy day, since … all days are
God’s. [Ohiyesa, of the Santee Dakota, 1911, quoted in T. C. McLuhan, Touch the Earth: A
Self-Portrait of Indian Existence. (New York: Outerbridge and Dienstfrey, 1971), p. 36.] 

4. It’s not like there’s going to be a separate Korean section in heaven … so I don’t think it is right
for us to have our own separate … [Korean churches or campus evangelical organizations].
[Anonymous second-generation Korean American college student, quoted in Rebecca Y.
Kim, “Made in the U.S.A.: Second-Generation Korean American Campus Evangelicals,” in
Jennifer Lee and Min Zhou, eds., Asian American Youth: Culture, Identity, and Ethnicity.
(New York: Routledge, 2004), p. 244.] 

165

5. Note: This passage is an excerpt from Lillian Hellman’s account of how she came to write a
new adaptation of Jean Anouilh’s play The Lark (L’Alouette in French). The speaker is
Anouilh’s agent, Dr. Van Loewen. At first, Van Loewen thought Hellman shouldn’t adapt the
play, but later on he agreed to have her do it.

…L’Alouette comes from the mind of a poet and must, therefore, be adapted by a poet.
[Lillian Hellman, Pentimento. (New York: New American Library, 1973), p. 166.]

6. Note: A nocturnal animal sleeps at night and is active during the day.

Because of the Aard-Wolf’s nocturnal habits it is rarely seen…. [Shell Guide to Wild Life.
(Nairobi: Injes May, 1976), p. 8.]

7. Many small dog breeds are long-lived and therefore may manifest symptoms associated with
age. [Doctors Foster & Smith, Catalogue (Summer 2005), p. 47.] 

8. …[M]any South Koreans have personal computers and therefore need not frequent cafés to
play video games…. [Mary Yu Danico and Linda Trinh Võ, “‘No Lattés Here’: Asian
American Youth and the Cyber Café Obsession,” in Jennifer Lee and Min Zhou, eds., Asian
American Youth: Culture, Identity, and Ethnicity. (New York: Routledge, 2004), p. 178.]

9. Note: The argument in this passage is boldfaced and underlined.

The great principle of American war strategy is: We have airplanes, therefore they must be
effective. [John Kenneth Galbraith, quoted in Studs Terkel, “The Good War”: An Oral
History of World War Two. (New York: Pantheon Books, 1984), p. 207.] 

10. Note: The argument in this passage is boldfaced and underlined.

The youngsters have the same brightly patterned black, orange, yellow, and pink skin as the
adults. Found in the southwestern United States and into Sonora, Mexico, gila monsters are
protected in the wild. Because they spend nearly 90 percent of their time in burrows, it is
difficult to verify their population numbers in the wild, but they are most likely
endangered. [Los Angeles Zoo and Botanical Gardens, Press Release, “Rare Gila Monsters
Hatch at L.A. Zoo,” February 17, 2004.]

11. …[T]he word Mafia came into Carl’s talk, but I had never heard it before and it therefore
meant nothing to me. [Lillian Hellman, Pentimento. (New York: New American Library,
1973), p. 14.] 

12. Los Angeles City Council District 14
We have often said that elected officials who have not been found derelict in their duties
deserve to serve at least two terms in office therefore our endorsement goes to the incumbent
Jose Huizar. [“EGP (Eastern Group Publications) Endorsements For March 6 Election,”
Northeast Sun (Los Angeles), March 1, 2007.]

166

13. Note: Stanley “Tookie” Williams was executed by the State of California in 2005 after having
been convicted of four murders, which he denied having committed. He was an early leader
of the Crips. While in prison, he renounced his gang membership and engaged in anti-gang
advocacy. As part of this effort, he authored or co-authored a number of books, including
some children’s books.

Some people are opposing Tookie’s death, saying he’s not guilty. [Christine Devine, Fox 11
News (Los Angeles), December 12, 2005.]

14. “I think if you rule … [a run for the governorship] out, you’re doing the wrong thing,”
[Warren] Beatty said. “If you rule it out, you’re saying, ‘I won’t serve the public even if
asked.’ ” [Laura Kurtzman, “Democrats Eye Actor as Answer to Schwarzenegger,” San Jose
Mercury News, May 28, 2005.] 

15. If FDR had lived, the cold war wouldn’t have developed the way it did, because Stalin would
have tried to get along with Roosevelt. [W. Averell Harriman, quoted in Studs Terkel, “The
Good War”: An Oral History of World War Two. (New York: Pantheon Books, 1984), p.
331.]

167

A Short Recap

In Chapter Two, you have learned the basic concepts used to evaluate arguments and you have
begun to learn some methods to apply these concepts. Now you are ready to start using these
concepts in a more precise and rigorous way than we have in Chapter Two. In Chapter Two, we
were mostly relying on our intuitions and our imaginations to determine the validity and
invalidity, or strength or weakness, of arguments. In Chapters Three and Four, we will study
techniques that will allow us to determine the validity and invalidity of certain kinds of
arguments in more precise and rigorous ways; we will learn techniques that guarantee we get the
right answer about whether the argument we’re testing is valid or invalid.

At this point, you should be able to:

♦ distinguish between criticisms of arguments according to which the arguments
have one or more false premises and criticisms according to which, assuming
the premises are all true, they do not support the conclusion

♦ define deductive argument

♦ define sound argument

♦ define unsound argument

♦ define valid argument

♦ define invalid argument

♦ understand the difference between validity and soundness

♦ make up counterexamples to demonstrate invalidity

♦ define inductive argument

♦ define compelling argument

♦ define uncompelling argument

♦ define strong argument

♦ define weak argument

♦ add unstated premises to deductive arguments

♦ add unstated premises to inductive arguments

168

ANSWERS TO SELECTED PRACTICE
PROBLEMS FOR CHAPTER TWO

Practice Problems Set 2-1

1. (1) One skater paints graffiti on a building.
___________________________________
(2) All skaters are criminals.

4. (1) You profess Christianity.
__________________________________________
(2) You have found an exclusive avenue to the truth.

6. (1) A person has HIV.
______________________
(2) That person has AIDS.

8. (1) A guy can bury a twenty-foot jumper or glide to the hoop like an angel.
____________________________________________________________
(2) He’s the one to tell you how to live.

10. (1) A governor doesn’t like the purpose of a National Guard deployment.
___________________________________________________________
(2) That governor can block the deployment.

Practice Problems Set 2-2

2. (1) A minor commits an act we think only an adult is capable of.
____________________________________________________
(2) That minor has the mental capacity of an adult.

Bohn criticizes this argument on the ground that the premise, assuming it is true, does not
support the conclusion.

4. (1) Renters can easily afford to pay higher rents.
_______________________________________
(2) Rent control gives renters an unfair break.

McManigal criticizes this argument on the ground that its premise is false.

169

5. (1) Deep Throat knew the Nixon White House.
______________________________________
(2) He worked within the Nixon White House.

Woodward criticizes this argument on the ground that the premise, assuming it is true, does

not support the conclusion.

7. (1) The anti-war movement had no strong Democratic Party spokesperson.
____________________________________________________________
(2) CNN didn’t have a responsibility to cover the anti-war movement.

Rendall criticizes this argument on the ground that the premise, assuming it is true, does not
support the conclusion.

9. (1) An openly gay teacher might (inadvertently or not) cause a closeted gay student to become
openly gay.

(2) The life of an openly gay person is a life of misery or suffering.

___________________________________________________________________________
(3) Openly gay teachers must be fired.

Mohr criticizes this argument on the ground that the premise, assuming it is true, does not
support the conclusion.

Practice Problems Set 2-3

1. Unsound, because premises (1) and (2) are both false

3. Unsound, because invalid and because premises (1) and (2) are both false

5. Sound

7. Unsound, because invalid

11. Unsound, because premise (1) is false

13. Sound

14. Unsound, because invalid and because premise (2) is false

Practice Problems Set 2-4

1. (1) All college students go to college.
(2) All college students are humans.
______________________________
(3) All humans go to college.

170

3. (1) Some humans are animals that can swim.
(2) Some animals that can swim aren’t mammals.
________________________________________
(3) Some humans aren’t mammals.

5. (1) If Los Angeles is in the U.S., then Los Angeles is in North America.
(2) If Los Angeles is in California, then Los Angeles is in the U.S.
___________________________________________________________
(3) If Los Angeles is in North America, then Los Angeles is in California.

7. (1) No snakes are dogs.
(2) Some dogs are animals with eyes.
___________________________________
(3) Some snakes are not animals with eyes.

9. (1) All college students are humans.
(2) No college students are human infants.
__________________________________
(3) No humans are human infants.

Practice Problems Set 2-5

1. Reconstruction with an unstated premise that makes the argument valid:

(1) Paul McCartney is one of the world’s most beloved artists and incomparable live
entertainers.

(2) The world’s most beloved artists and incomparable live entertainers always deliver
inspirational performances. (unstated)

______________________________________________________________________
(3) He will deliver an inspirational performance.

Reconstruction with an unstated premise that makes the argument strong:
(1) Paul McCartney is one of the world’s most beloved artists and incomparable live
entertainers.

(2) The world’s most beloved artists and incomparable live entertainers usually deliver
inspirational performances. (unstated)

______________________________________________________________________
(3) He will deliver an inspirational performance.

171

3. Reconstruction with an unstated premise that makes the argument valid:

(1) All days are God’s.
(2) If all days are God’s, then there is no need for setting apart one day in seven as a holy day.

(unstated)
__________________________________________________________________________
(3) There is no need for setting apart one day in seven as a holy day.

Reconstruction with an unstated premise that makes the argument strong:

(1) All days are God’s.
(2) If all days are God’s, then there is probably no need for setting apart one day in seven as a

holy day. (unstated)
___________________________________________________________________________
(3) There is no need for setting apart one day in seven as a holy day.

4. Reconstruction with an unstated premise that makes the argument valid:

(1) There isn’t going to be a separate Korean section in heaven.
(2) If it’s right for us to have our own separate Korean churches or campus evangelical

organizations, then there is going to be a separate Korean section in heaven. (unstated)

__________________________________________________________________________
(3) It’s not right for us to have our own separate Korean churches or campus evangelical

organizations.

Reconstruction with an unstated premise that makes the argument strong:
(1) There isn’t going to be a separate Korean section in heaven.
(2) If it’s right for us to have our own separate Korean churches or campus evangelical

organizations, then there is probably going to be a separate Korean section in heaven.
(unstated)

__________________________________________________________________________
(3) It’s not right for us to have our own separate Korean churches or campus evangelical
organizations.

7. Reconstruction with an unstated premise that makes the argument valid:

(1) Many small dog breeds are long-lived.
(2) All long-lived dog breeds may manifest symptoms associated with age. (unstated)
____________________________________________________________
(3) Many small dog breeds may manifest symptoms associated with age.

Reconstruction with an unstated premise that makes the argument strong:

(1) Many small dog breeds are long-lived.
(2) Most long-lived dog breeds may manifest symptoms associated with age. (unstated)
_____________________________________________________________
(3) Many small dog breeds may manifest symptoms associated with age.

9. Reconstruction with an unstated premise that makes the argument valid:

(1) The U.S. military has airplanes.

172

(2) Everything the U.S. military has is effective. (unstated)
_______________________________________
(3) Airplanes are effective.

Reconstruction with an unstated premise that makes the argument strong:

(1) The U.S. military has airplanes.
(2) Most things the U.S. military has are effective. (unstated)
________________________________________
(3) Airplanes are effective.

11. Reconstruction with an unstated premise that makes the argument valid:

(1) I had never heard the word ‘Mafia’ before it came into Carl’s talk.
(2) All words that meant something to me were words I had heard before. (unstated)
___________________________________________________________
(3) The word ‘Mafia’ meant nothing to me when it came into Carl’s talk.

Reconstruction with an unstated premise that makes the argument strong:

(1) I had never heard the word ‘Mafia’ before it came into Carl’s talk.
(2) Most words that meant something to me were words I had heard before. (unstated)
_____________________________________________________________
(3) The word ‘Mafia’ meant nothing to me when it came into Carl’s talk.

14. Reconstruction with an unstated premise that makes the argument valid:

(1) If you rule out a run for the governorship, then you’re saying, “I won’t serve the public
even if asked.”

(2) If you’re saying, “I won’t serve the public even if asked,” then you’re doing the wrong
thing. (unstated)

_______________________________________________________________________
(3) If you rule out a run for the governorship, then you’re doing the wrong thing.

Reconstruction with an unstated premise that makes the argument strong:
(1) If you rule out a run for the governorship, then you’re saying, “I won’t serve the public
even if asked.”

(2) If you’re saying, “I won’t serve the public even if asked,” then you’re probably doing the
wrong thing. (unstated)

__________________________________________________________________________
(3) If you rule out a run for the governorship, then you’re doing the wrong thing.

173

SAMPLE MULTIPLE CHOICE
QUESTIONS FOR CHAPTER TWO

1. What kind of criticism does Caitlin White raise in the following passage?

Just because I won’t be getting a dozen roses or a ring from Tiffany’s [for Valentine’s
Day] doesn’t mean that I’m not loved. [Caitlin White, “Just Say No to Valentine’s Day,”
Orion (California State University, Chico), February 14, 2007.]

a. White criticizes the argument on the ground that its premise is false.
b. White criticizes the argument on the ground that the premise, assuming it is true, does not

support the conclusion.

2. What kind of criticism does David Zeiler raise in the following passage?

Few hackers attack Mac, but just because it’s a niche product, that doesn’t make it
invulnerable. [David Zeiler, “What, Me Worry,” Baltimore Sun, August 21, 2003.]

a. Zeiler criticizes the argument on the ground that its premise is false.
b. Zeiler criticizes the argument on the ground that the premise, assuming it is true, does not

support the conclusion.

3. What kind of criticism does The Day raise in the last paragraph of the following passage?

The fact that that a bill legalizing same-sex marriage will not be approved by the state
legislature this year is unfortunate, yet support is clearly building and there is a sense of
inevitability that ultimately such a law will be passed.

Perhaps this is to be expected. It is only two years since the state first approved a law allowing
same-sex couples to enter civil unions with all the legal rights of marriage, but not the name.
It takes times for consensus to build and for a majority of state lawmakers to become
comfortable enough with the concept to take the logical next step.

The debate over civil unions featured the illogical argument that allowing same-sex couples to
make a legal commitment to one another would somehow undermine families and traditional
heterosexual marriages. The reality has been that civil unions have had no effect on traditional
couplings. There has been no great social upheaval. [“Legislature Misses Opportunity,”
Editorial, The Day (Connecticut, May 21, 2007.]
a. The Day the argument on the ground that its premise is false.
b. The Day criticizes the argument on the ground that the premise, assuming it is true, does

not support the conclusion.

174

4. What kind of criticism does Christine Brennan raise in the last paragraph of the following
passage?

Even as the USGA [United States Golf Association] pumps millions into programs designed
to encourage girls and African-Americans to take up golf, the organization gave the men $6.5
million in prize money at their Open last week — but will give the women $3.1 million at
theirs this week. [Michael] Campbell earned $1.17 million last Sunday. [Annika] Sorenstam
or whoever beats her will earn $560,000 this Sunday.

The USGA says the reason for the discrepancy is that the men’s Open makes money and the
women’s Open loses money, but that argument goes only so far when it’s coming from a not-
for-profit national governing body whose mission is to open up the game to all. Every other
national governing body for a sport in this country pays men and women equally, even if the
women draw more fans, like in gymnastics and figure skating. The U.S. Tennis Association
has paid equally at its U.S. Open since 1973. [Christine Brennan, “Sorenstam May Force
Equality in Golf Yet,” USA Today, June 22, 2005.]

a. Brennan criticizes the argument on the ground that it has a false premise.
b. Brennan criticizes the argument on the ground that the premises, assuming they are true, do

not support the conclusion.

5. What kind of criticism does Katt Hemman raise in the following passage?

The argument that it’s OK to track kids [with cellular services that use global positioning
satellites] because it’ll keep a few of them from being kidnapped or making mischief is
specious reasoning, says 17-year-old Katt Hemman, from Hutchinson, Kan. It’s the same
argument that the Bush administration makes in defending warrantless wiretapping, she says.
A marginal increase in safety isn’t worth forfeiting our civil rights, and adults who balk at
being spied on and then turn around and spy themselves are hypocrites. [Steven Barrie-
Anthony, “Cellphones: Just a Leash for Children?,” Los Angeles Times, June 21, 2006.]

a. Hemman criticizes the argument on the ground that its premise is false.
b. Hemman criticizes the argument on the ground that the premise, assuming it is true, does

not support the conclusion.

175

6. What kind of criticism does Michael Cloud raise in the following passage? Note: A syllogism
is a kind of argument we will study in Chapter Three.

A well-known libertarian scholar once told me:

“Voting is an act of force. Libertarians are opposed to force. Ergo, true libertarians don’t
vote.”

His syllogism was, as H. L. Mencken wrote, “…simple, neat, and wrong.”

Why?

“War is simply the continuation of politics by other means,” wrote Carl von Clausewitz.

True, but libertarians recognize that the opposite is also true:

“Politics is war by other means.”

Voting is conflict by ballots, not bullets. Big Government is domination and looting by the
victors. Voting is force.

But the argument misstates and misrepresents the libertarian principle. Libertarians oppose
the INITIATION of force. Libertarians recognize and endorse the right of self-defense.

For true libertarians, for champions of small government – voting is an act of self-defense.
[Michael Cloud, “Is Voting Un-Libertarian?,” Free Market News Network (Florida), February
23, 2007.]

a. Cloud criticizes the argument on the ground that it has a false premise.
b. Cloud criticizes the argument on the ground that the premises, assuming they are true, do

not support the conclusion.

7. Is the following sentence true or false?

A valid argument must have all true premises.

a. Yes, this is true.
b. No, this is false.

8. Is the following sentence true or false?

A sound argument must have all true premises.

a. Yes, this is true.
b. No, this is false.

176

9. Is the following sentence true or false?

Every argument with all true premises and a true conclusion is valid.

a. Yes, this is true.
b. No, this is false.

10. Is the following sentence true or false?

Every argument with all true premises and a false conclusion is invalid.

a. Yes, this is true.
b. No, this is false.

11. Is the following sentence true or false?

A sound argument must be valid.

a. Yes, this is true.
b. No, this is false.

12. Is the following sentence true or false?

A valid argument must be sound.

a. Yes, this is true.
b. No, this is false.

13. Is the following sentence true or false?

A valid argument cannot have a false conclusion.

a. Yes, this is true.
b. No, this is false.

14. Is the following sentence true or false?

An unsound argument must be invalid.

a. Yes, this is true.
b. No, this is false.

15. Is the following sentence true or false?

An unsound argument must have at least one false premise.

a. Yes, this is true.
b. No, this is false.

177

16. Pick the multiple choice that correctly completes the following.

Imagine that you see an argument you recognize as valid, but you do not know the truth
value of one of its premises. You are asked whether the argument is sound or unsound. You
should answer: _____________________.

a. “The argument is sound.”
b. “The argument is unsound.”
c. “I don’t know whether the argument is sound or unsound.”

17. Pick the multiple choice that correctly describes the following argument.

(1) All snakes are reptiles.
(2) All reptiles are animals.
______________________
(3) All snakes are animals.

a. This argument is unsound because, although it is valid, it has at least one false premise.
b. This argument is unsound because, although all of its premises are true, it is invalid.
c. This argument is unsound because it is invalid and it has at least one false premise.
d. This argument is sound.

18. Pick the multiple choice that correctly describes the following argument.

(1) All California State University, Northridge (CSUN), students are students.
(2) All California State University, Los Angeles (CSULA), students are students.
_________________________________________________________________
(3) All CSUN students are CSULA students.

a. This argument is unsound because, although it is valid, it has at least one false premise.
b. This argument is unsound because, although all of its premises are true, it is invalid.
c. This argument is unsound because it is invalid and it has at least one false premise.
d. This argument is sound.

19. Pick the multiple choice that correctly describes the following argument.

(1) All college students are students.
(2) You are a student.
_____________________________
(3) You are a college student.

a. This argument is unsound because, although it is valid, it has at least one false premise.
b. This argument is unsound because, although all of its premises are true, it is invalid.
c. This argument is unsound because it is invalid and it has at least one false premise.
d. This argument is sound.

178

20. Pick the multiple choice that correctly describes the following argument.

(1) Your logic teacher has four legs and bright purple skin.
(2) Everyone who has four legs and bright purple skin is 100 feet tall.
________________________________________________________
(3) Your logic teacher is 100 feet tall.

a. This argument is unsound because, although it is valid, it has at least one false premise.
b. This argument is unsound because, although all of its premises are true, it is invalid.
c. This argument is unsound because it is invalid and it has at least one false premise.
d. This argument is sound.

21. Pick the multiple choice that correctly describes the following argument.

(1) If Long Beach is in California, then Long Beach is in Japan.
(2) Long Beach is in California.
___________________________________________________
(3) Long Beach is in Japan.

a. This argument is unsound because, although it is valid, it has at least one false premise.
b. This argument is unsound because, although all of its premises are true, it is invalid.
c. This argument is unsound because it is invalid and it has at least one false premise.
d. This argument is sound.

22. Pick the multiple choice that correctly describes the following argument.

(1) If Las Vegas is in California, then Las Vegas is in the United States.
(2) Las Vegas is not in California.
_________________________________________________________
(3) Las Vegas is not in the United States.

a. This argument is unsound because, although it is valid, it has at least one false premise.
b. This argument is unsound because, although all of its premises are true, it is invalid.
c. This argument is unsound because it is invalid and it has at least one false premise.
d. This argument is sound.

23. Pick the multiple choice that correctly describes the following argument.

(1) If Long Beach is in California, then Long Beach is in the United States.
(2) Long Beach is in the United States.
_____________________________________________________________
(3) Long Beach is in California.

a. This argument is unsound because, although it is valid, it has at least one false premise.
b. This argument is unsound because, although all of its premises are true, it is invalid.
c. This argument is unsound because it is invalid and it has at least one false premise.
d. This argument is sound.

24. Pick the multiple choice that correctly fills in the blank in the following.

A ____________ argument is a strong argument with all true premises.

a. deductive
b. sound

179

c. inductive
d. strong
e. compelling

25. Pick the multiple choice that correctly fills in the blank in the following.

A ____________ argument is a valid argument with all true premises.

a. deductive
b. sound
c. inductive
d. strong
e. compelling

26. Pick the multiple choice that correctly fills in the blank in the following.

A ____________ argument always has a true conclusion.

a. sound
b. valid
c. compelling
d. strong

27. Is the following sentence true or false?

Sound arguments are the only arguments that give us good reasons to believe their
conclusions.

a. Yes, this is true.
b. No, this is false.

28. Pick the multiple choice that correctly fills in the blank in the following.

By definition, every __________ argument with an unstated premise is valid.

a. deductive
b. inductive

180

29. Is the following sentence true or false?

By definition, every inductive argument with an unstated premise is compelling.

a. Yes, this is true.
b. No, this is false.

30. Assume that the following argument is deductive. Identify its unstated premise.

(1) Dervish is a cat.
____________________
(2) Dervish is an animals.

a. All cats are animals.
b. All animals are cats.
c. Dervish is a cat.
d. Dervish is an animal.

31. Assume that the following argument is deductive. Identify its unstated premise.

(1) Dervish is a cat.
________________________
(2) Dervish is not an elephant.

a. No cats are elephants.
b. Most cats aren’t elephants.
c. Dervish is a cat.
d. Dervish is a mammal.

32. Assume that the following argument is inductive. Identify its unstated premise.

Abraham Lincoln was not a communist, because he was a president of the United States.

a. No presidents of the United States have been communists.
b. Almost no presidents of the United States have been communists.
c. Most presidents of the United States have been communists.
d. All presidents of the United States have been communists.

33. Assume that the following argument is deductive. Identify its unstated premise.

…Bethe … was … a third cousin and therefore to be trusted. [Lillian Hellman, Pentimento.
(New York: New American Library, 1973), p. 7.]

a. All third cousins are to be trusted.
b. No third cousins are to be trusted.
c. Most third cousins are to be trusted.
d. Most third cousins are not to be trusted.

34. Assume that the following argument is deductive. Identify its unstated premise. Note: The
speaker is a fictional character called the Scarecrow.

181

I am only a Scarecrow, stuffed with straw. Therefore I have no brains…. [L. Frank Baum,
The Wizard of Oz. (1900; reprinted: New York: Grosseet and Dunlap, 1963), p. 89.]

a. Everything stuffed with straw has brains.
b. Nothing stuffed with straw has brains.
c. Most things stuffed with straw have brains.
d. Most things stuffed with straw don’t have brains.

35. Assume that the following argument is deductive. Identify its unstated premise.

Nuclear war could destroy this beautiful Earth and its people. We must eliminate these
weapons. [Ann Edelman, Letter to the Editor, Los Angeles Times, October 19, 2006.]

a. If nuclear war could destroy this beautiful Earth and its people, then we must eliminate
nuclear weapons.

b. If we must eliminate nuclear weapons, then nuclear war could destroy this beautiful Earth
and its people.

c. We must eliminate nuclear weapons.
d. Nuclear war could destroy this beautiful Earth and its people.

36. Assume that the following argument is inductive. Identify its unstated premise.

Cooks love beets because they add a bit of color at a time of year when that is sadly lacking.
[“A Prime Time for Snappy Picks,” Los Angeles Times, June 21, 2006.]

a. Cooks love beets.
b. Beets add a bit of color at a time of year when that is sadly lacking.
c. Cooks love all foods that add a bit of color at a time of year when that is sadly lacking.
d. Cooks love most foods that add a bit of color at a time of year when that is sadly lacking.

37. Assume that the following argument is inductive. Identify its unstated premise.

It is probably true that the least destructive nuclear weapons are the most dangerous, because
they make it easier for a nuclear war to begin. [Freeman Dyson, “Reflections: Weapons and
Hope,” The New Yorker (February 6, 1984).]

a. If the least destructive nuclear weapons make it easier for a nuclear war to begin, then they
are the most dangerous.

b. If the least destructive nuclear weapons make it easier for a nuclear war to begin, then they
are probably the most dangerous.

c. The least destructive nuclear weapons make it easier for a nuclear war to begin.
d. The least destructive nuclear weapons are the most dangerous.

182

38. Assume that the following argument is deductive. Identify its unstated premise.

[Susan B.] Anthony was not a lady manager and therefore … could not participate in the
board’s meeting. [Erik Larson, The Devil in the White City. (New York: Crown Publishers,
2003), p. 284.]

a. If Susan B. Anthony could participate in the board’s meeting, then she was a lady manager.
b. If Susan B. Anthony could participate in the board’s meeting, then she probably was a lady

manager.
c. If Susan B. Anthony was a lady manager, then she could participate in the

board’s meeting.

d. If Susan B. Anthony was a lady manager, then she probably could participate in the

board’s meeting.

39. Assume that the following argument is deductive. Identify its unstated premise.

If your father is not close to you, you will not be close with other people because you fear
you will be emotionally or physically violated. [Henry Waweru, quoted in Mutanu Musyimi,
“Kenya: The Danger of Dysfunctional Families,” East African Standard (Nairobi), March 29,
2007.]

a. If your father is not close to you, you will

not be close with other people.

b. If your father is not close to you, then you fear you will be emotionally or physically

violated by others.
c. If you fear you will be emotionally or physically violated by others, then you will not be

close with other people.
d. If you fear you will be emotionally or physically violated by others, then you probably will

not be close with other people.

40. Assume that the following argument is deductive. Identify its unstated premise.

If … [Charles Manson] can’t follow the simple rules of prison, how can we expect him to
follow the rules of society? I think the answer is obvious. We can’t. [Los Angeles Deputy
District Attorney, Stephen Kay, November 30, 1982, speaking at a parole hearing for Charles
Manson, quoted in Edward George with Dary Matera, Taming the Beast: Charles Manson’s
Life Behind Bars. (New York: St. Martin’s Griffin, 1998), p. 166.]

a. If Charles Manson can’t follow the simple rules of prison, then we can’t expect him to
follow the rules of society.

b. If Charles Manson can’t follow the simple rules of prison, then we probably can’t expect
him to follow the rules of society.

c. Charles Manson can’t follow the simple rules of prison.
d. Charles Manson can’t follow the rules of society.

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ANSWERS TO SAMPLE
MULTIPLE CHOICE QUESTIONS

FOR CHAPTER TWO
1. b 16. c 31. a

2. b 17. d 32. b

3. a 18. b 33. a

4. b 19. b 34. b

5. b 20. a 35. a

6. a 21. a 36. d

7. b 22. b 37. b

8. a 23. b 38. a

9. b 24. e 39. c

10. a 25. b 40. c

11. a 26. a

12. b 27. b

13. b 28. a

14. b 29. b

15. b 30. a