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 Americans currently live in Nevada.  Aretha Franklin (the famous singer) is an American. So, it is likely Aretha Franklin currently lives in Nevada.”

 

      Inductive or Deductive? (You write)           Inductive

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 Americans currently live either in Nevada or California.  The famous American singer Aretha Franklin does not live in Nevada. So, Aretha Franklin currently lives in California.”

 

      Inductive or Deductive? (You write)           Deductive

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.

 

   

Sandy's X10 Host Home Page | Sandy's Google Sites Home Page
Questions or comments? sandy_lafave@yahoo.com