Project #39010 - Philosophy

PHL1090

Exercise 1.4

Name:  ___________________________

 

A.  For each of the following deductive arguments:

1)   Formalize it, changing the wording if necessary, and providing any unstated premises.

2)   Show which is the principle premise, and which is the case premise.

3)   Say whether the argument is sound or not, and why you think so.  (Remember that a sound argument is valid, and has only true premises.) 

(5 points possible)

Example (from Hurley’s exercise 1.3):

We tell people not to speed, but equip cars with air bags in case they do.  So what’s wrong with telling kids not to have sex, but making Plan B available in case they do?  (Susan Beck, letter to the editor)

 

P1:  If some precautionary rule is true about driving, then it is also true about sex. [unstated principle premise]

P2:  We equip cars with air bags, in case drivers speed (and crash).  [case]

C:   We should make Plan B available to young people, in case they engage in sex (resulting in pregnancy).

 

Valid?  Why or why not?   This argument is valid.  IF it were true that precautionary rules about driving were also true about sex, THEN it would follow that we should make Plan B available to young people, since there would be a contradiction otherwise.

 

Sound?  Why or why not?  The argument is not sound, since P1 is not true.  The claim here is that all precautionary rules about driving are also true about safe sex. Consider speeding laws. Enough said.

 


 

 

1)    Everyone knows that witches have warts.  Maude has a wart, so we can assume that Maude is a witch.

P1: 

P2: 

C:  

 

Valid?  Why or why not?  

 

Sound?  Why or why not? 

 


 

 

2)    Chicago is a city in Michigan and Michigan is a part of the United States.  Therefore, Chicago is a city in the United States.  (This is Hurley, exercise 1.4.)

 

Hint:  Consult a map if you are unsure of where Chicago is.

 

 

P1: 

P2: 

C:  

 

Valid?  Why or why not?  

 

Sound?  Why or why not? 

 


 

 

B.    For each of the following inductive arguments, determine whether it is strong or weak, cogent or uncogent.  (All are from Hurley’s exercise 1.4.)   (3 points possible)

 


 

 

1)    The vast majority of Rose Bowl games (in Pasadena, California) have been played in freezing cold weather.  Therefore, probably the next Rose Bowl game will be played in freezing cold weather.

Weak or strong?  Why?

Cogent or uncogent?  Why?


 

 

2)    Constructing the great pyramid at Giza required lifting massive stone blocks to great heights.  Probably the ancient Egyptians had some antigravity device to accomplish this feat.

Weak or strong?  Why?

Cogent or uncogent?  Why?


 

 

3)    When Neil Armstrong landed on the moon, he left behind a gold-plated Schwinn bicycle, which he used to ride around on the moon’s surface.  Probably that bicycle is still up there on the moon.

Weak or strong?  Why?

Cogent or uncogent?  Why?


 

 

C.    For each of the following arguments, determine whether it is inductive or deductive. (No need to formalize.) If it is deductive, determine whether it is valid or invalid. If inductive, determine whether it is strong or weak.  (From Hurley’s exercise 1.4)   (2 points possible)


 

 

1)     By accident, Karen baked her brownies two hours longer than she should have.  Therefore, they have probably been ruined.

Deductive or inductive?  Why?

Valid?  Strong?  Why?


 

 

2)   The Broadway Theatre marquee says that The Phantom of the Opera is playing nightly.  Therefore, it must be the case that Phantom is playing there tonight.

Deductive or inductive?  Why?

Valid?  Strong?  Why?


 

 

3)   If acupuncture is hocus pocus, then acupuncture cannot relieve chronic pain.  But acupuncture can relieve chronic pain.  Therefore, acupuncture is not hocus pocus.

Deductive or inductive?  Why?

Valid?  Strong?  Why?


 

 

4)   Since John loves Nancy and Nancy loves Peter, it follows necessarily that John loves Peter.

Deductive or inductive?  Why?

Valid?  Strong?  Why?


 

Subject Philosophy
Due By (Pacific Time) 09/03/2014 12:00 am
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