PART I (12 points). Determine whether
the following passages contain arguments. If the passage contains an argument,
underline the conclusion. If the passage
does not contain an argument, explain why.
1.
Martin
Scorcese directed the three Godfather
movies. I really liked the first two, but I didn’t care for the third one.
Scorcese also directed Casino, but
that was too violent for me.
No argument because nothing is being claimed to prove that something else is so.
2.
The media – newspapers, radio, television, and the Internet – are
essential for a democracy. They are the critical link
between the people and their government.
They provide information and analysis about policy issues, and they also
sensitize policyholders to public opinion – which enables them to respond to
the needs and desires of the population.
Finally, the media play a critical role in reporting and evaluating the
decisions of government.
3.
Cancer is not one disease but many. Some forms are
particularly susceptible to radiation therapy.
Radiation is carefully aimed at the cancerous tissue, and exposure of
normal cells is minimized. If the cancer cells are killed by the destructive
effects of the radiation, the malignancy is halted.
No argument because no conclusion. Loosely associated statements.
4.
For both plants and animals whose ecosystem is the sea surface,
sinking into deep water usually means death. Plant cells
cannot photosynthesize in the dark depths. Fishes and other animals that
descend lose contact with the main surface food supply and themselves become
food for strange deep-living predators.
5.
Sometimes
you can’t see the stars at night because the sky is cloudy.
Not an argument because the fact that sometimes you
can’t see the starts at night does not require proof. This is an explanation.
6.
Interest rates will probably be rising in the near future. This is because the Treasury
Department has reported an increase in the money supply, and an increase in the
money supply is nearly always followed by an increase in interest rates.
PART II (30 points). Analyze the following arguments and answer
the questions that follow. Explain your
answers. NOTE: If an argument is invalid, you can answer the “why?” portion
of the question by using refutation by logical analogy.
HINT: You can
often use the general type of
argumentation — argument from analogy, generalization from a sample, causal
argument, argument from signs, argument from authority, categorical syllogism,
disjunctive syllogism, hypothetical syllogism, etc. — to help determine whether
the argument is inductive or deductive.
See the following examples.
FIRST EXAMPLE:
Question: “Most
Why? The arguer claims that
the premises, if true, make the conclusion likely. This is the defining characteristic
inferential claim of inductive arguments.
Logically
correct? (I.e., if deductive, valid or invalid; if inductive, strong or weak –
choose one)? (You write) Strong
Why/
why not? In this argument, the conclusion really
would be likely if the premises were true.
SECOND EXAMPLE
Question: “All
Why? The argument is a disjunctive syllogism – one
of the characteristic deductive forms.
Logically
correct? (valid or invalid, strong or weak – choose one)? (You write) valid
Why/ why
not? Disjunctive syllogism is a valid form so all
its substitution instances are valid arguments. The argument is
obviously not sound, however, because the first premise is obviously false.
1.
Since
some politicians are honest people, and no honest people are eloquent
statesmen, it follows that no politicians are eloquent statesmen.
Is this argument inductive or deductive? Deductive
Why? It’s a categorical
syllogism.
Is this argument logically correct (valid or
invalid, strong or weak – choose one)? Explain why. The argument is
invalid. You can see with a
counterexample: substitute “doctors” for “politicians”; “women” for “honest people”;
and “men” for “eloquent statesmen”.
2.
When
Tom drove his car out of the driveway this morning there were oil stains on the
pavement. These stains were not there when he drove the car in the night
before. We conclude that Tom’s car is leaking oil.
Is this argument inductive or deductive? Inductive
Why? It’s a causal argument.
Is this argument logically correct (valid or
invalid, strong or weak – choose one)? Explain why. The argument is strong because, other things being
equal, if the premises are true, the conclusion is probably true.
3.
Over
the years, I have bought many pairs of Adidas running shoes and every pair has
been comfortable and long-wearing. So
the next pair of Adidas I buy will probably be comfortable and long-wearing
too.
Is this argument inductive or deductive? Inductive
Why? This
is an argument by analogy, or a prediction.
Is this argument logically correct (valid or
invalid, strong or weak – choose one)? Explain why. The argument is strong because if the premises are
true, the conclusion is probably true.
4.
Highway 14 is a paved road. But this map says the road to Springtown is
a gravel road. So there’s no way Highway 14 can be the road to Springtown.
Is this argument inductive or
deductive? Inductive
Why? It’s
an argument from authority (the map) or signs.
Is this argument logically correct (valid or
invalid, strong or weak – choose one)? Explain why. The argument is strong if the map is current.
5.
Since Ann and Bill have the same natural parents, it follows that they’re
siblings.
(NOTE: The word
“sibling” means “a brother or sister”.)
Is this argument inductive or
deductive? Deductive
Why? Argument by definition.
Is this argument logically correct (valid or
invalid, strong or weak – choose one)? Explain why. The argument is valid
because the conclusion must be true if the premises are true.
PART III (20 points, 10 each). Use the counterexample method to prove the
following arguments invalid.
1. All
college professors are teachers, so all teachers are educators, since all
college professors are educators.
The argument form is
All C are T.
All C are E.
Therefore all T are E.
Note
that the conclusion is “all teachers are educators”.. You know this because of
the conclusion indicator word “so”.
Substitute
“Animals” for T
“Dogs” for C
“Mammals” for E
This
yields All dogs are animals.
All dogs are mammals.
So all animals are
mammals.
In
the new argument the premises are true but the conclusion is false.
2. All
people have a heart, but my Batman action figure isn’t a person, so my Batman
action figure doesn’t have a heart.
Substitute
any non-human being with a heart (e.g., your dog or cat) for “my Batman action
figure” and you get true premises and a false conclusion.
PART IV (22 points, 2 points each).
Multiple-choice.
1
Which of the following is a sufficient condition for passing a class?
A. enrolling
in the class
B. attending
class at least once a week
C. doing
all the homework
D. avoiding
personal problems in one’s work or love life
E. earning
a final grade of B
2.
Which of the following is a necessary condition for passing a class?
A. studying
the material the night before the final exam
B. enrolling
in the class
C. avoiding
personal problems in one’s work or love life
D. participating
in a study group
E. getting
a C on the final exam
3.
Which of the following always occurs in a valid argument?
A. true
premises, true conclusion
B. true
premises, false conclusion
C. false
premises, false conclusion
D. false
premises, true conclusion
E. none
of the above
4.
Which of the following types of argument is not typically inductive?
A. Hypothetical syllogism
B. Argument from analogy
C. Causal inference
D. Argument from authority
E. Prediction
6. Which of the following is not a conclusion
indicator?
A. therefore
B. since
C. thus
D. implies
that
E. accordingly
7.
A deductive argument always proceeds from
A. the
particular to the general
B. the
general to the particular
C. the
particular to the particular
D. the
general to the general
E. none
of the above
9.
If a deductive argument has a true conclusion, then we know the argument
is
A. sound
B. valid
C. strong
D. cogent
E. none
of the above
10. Suppose you are following the counterexample
method to find out if a particular agument form is valid. You find a
substitution instance of a particular argument form. Your substitution instance
has all true premises and a true conclusion. This means:
A. the
argument form is valid
B. the
argument form is strong
C. the
argument form is sound
D. your
substitution instance tells you nothing about the argument form’s validity
E. the
argument form is true
11.
If an inductive argument has a false premise then we know the argument
is
A. weak
B. unsound
C. invalid
D. uncogent
E. strong
PART V
(16 points, 2 points each). True or false?
1. __T___ All sound arguments are
valid.
2. __F___ An inductive argument is one
in which the arguer claims that the conclusion
must be true if the premises are true.
3. __F___ The words “therefore”,
“hence”, “as”, “since”, and “thus” are all conclusion
indicators.
4. __T___ If an argument is valid,
then if the premises are true, the conclusion must be
true.
5. __F___ Any argument with a true
conclusion and correct deductive logic is sound.
6. ___F__ The terms “inference” and “argument”
mean exactly the same thing.
7. ___T__ A
valid argument can have false premises and a false conclusion,
8. __T___ In an explanation, the explanandum
usually expresses an accepted matter of fact.