Syllogisms

Philosophy, Reasoning and Critical Thinking

Year 2

Philosophy fallacies

Solution

Hello,

I've pasted below the exercises and my comments.  I hope you find the
comments helpful.  Don't hesitate to ask for clarification within this
post.  Just ask Admin., and they can send me an email.

Thanks!

Mia

1.       We can recognize that athletes that participate in sports
must be given special consideration within our grading system, or we can
let the university sink into athletic oblivion.

h.       False dilemma

You are correct.  There is a “middle” or “third way” through
this dilemma.  The false dilemma is that we either give special
consideration to student athletes when if comes to grades, or the
university will “sink into athletic oblivion” as if the only way for
the university to have a successful athletic program is if we let
student athletes slack off on studies.

2.       I don't know what colleges are teaching these days! I
have just received a letter of application from a young man who
graduated from the state university last June. It was a wretched
letter--badly written, with elementary errors in spelling, punctuation,
and grammar. The state university does not deserve the tax support that
it is getting.

j.         Hasty generalization



3.       All right-thinking people will support the Board of
Education's decision to destroy novels in the school libraries that are
offensive to the moral standards of the community. If there were an
epidemic of typhoid, the health authorities would be expected to do
everything in their power to wipe it out. Pornography is worse than
typhoid, since it corrupts the minds and morals of the young, not just
their bodies. The school board is to be applauded for their prompt
action in wiping out this moral disease.

g.       Equivocation



4.       Despite endless efforts, no one has been able to prove
that God exists; we may just as well stop trying and accept the truth:
there is no God.

l.         Ad ignorantium

You are correct!

5.       Alicia started gaining more weight than ever when she
started taking Slimdown; the stuff must be fattening!

c.       Post hoc ergo propter hoc



6.       No sensible person would support the Equal Rights
Amendment. If it were to pass, we would have women in combat and unisex
bathrooms. Eventually, we would not even be able to tell the women from
the men!

i.         Black and white (slippery slope)

You are correct!

7.       How can Clinton be leading this country! He's a
draft-dodging, pot-smoking, womanizer!!

d.       Attacking the person

You are correct!

8.       Michael Jordan wore that brand, so those must to be the
best basketball shoes.

f.         Non sequitur



9.       The difference in the outcome was Jefferson's missed
field goal. If he had put it through, we'd be going to the Super Bowl.

k.       Contrary-to-fact hypothesis

You are correct!

10.   Don't ignore the woman who gave you birth, raised you, loved you
then, and loves you still. Remember your mom on Mother's Day.

m.  Appeal to emotion

You are correct!

11.   So what if I didn't claim all of the money I earned on my taxes?
Lots of people underreport their income.

e.       Two wrongs

You are correct!

12.   That's gotta be a great line of clothes. Have you seen the
prices and the people endorsing it?

b.       Appeal to authority

You are correct!

MATCHING LIST FOR FINAL

Each argument commits only one fallacy, and each fallacy is only used
once.

a.       False analogy

b.       Appeal to authority

c.       Post hoc ergo propter hoc

d.       Attacking the person

e.       Two wrongs

f.         Non sequitur

g.       Equivocation

h.       False dilemma

i.         Black and white (slippery slope)

j.         Hasty generalization

k.       Contrary-to-fact hypothesis

l.         Ad ignorantium

m.  Appeal to emotion

To be a valid syllogism, the conclusion must be proven by the reasons.
Carefully study the following syllogisms and decide if they are valid or
invalid:

 

1.       All zebras are striped animals.

No zebras are polar bears.

Therefore, no polar bears are striped animals.

 invalid

 

2.       All clowns are funny individuals.

Some sad people are clowns.

Therefore, some sad people are funny individuals.

 valid

 

3.       Some sticky substances are yucky things.

All taffy is a sticky substance.

Therefore, some taffy is a yucky thing.

 invalid

 

4.       All items made of gold are expensive items.

Some rings are items made of gold.

Therefore, some rings are expensive items.

 Valid

5.       All flies are winged creatures.

All butterflies are winged creatures.

Therefore, all butterflies are flies.

invalid

 

The following are examples of syllogistic arguments that are missing the
conclusions. Study the two reasons very carefully and complete the
syllogism with the conclusion that logically follows.

 

6.       All fragile things are breakable things.

Some glasses are fragile things.

Therefore, some glasses are breakable things.

 

 

7.       All mammals are warm-blooded animals.

All whales are mammals.

Therefore, all whales are warm blooded animals.

 

 

8.       All books are things with pages.

Some books are mysteries.

Therefore, some mysteries are things with pages.

 

 

9.       All flowers are pretty objects.

All pansies are flowers.

Therefore, all pansies are pretty flowers.

 

 

10.   No animals are plants.

All sheep are animals.

Therefore, no sheep are plants.

 

 HYPOTHETICAL SYLLOGISMS—CONDITIONAL ARGUMENTS

 

Hypothetical syllogisms (conditional arguments) can have two valid and
two invalid structures. The two valid structures are affirming the
antecedent (modus ponens) and denying the consequent (modus tollens).
The two invalid structures, or fallacies, are denying the antecedent and
affirming the consequent. Determine if the arguments below are valid or
invalid and what form they take. The first one has been done for you.

(NOTE: The term "modus pollens" has been used in some texts as a version
of "modus ponens." For the purposes of this exercise, "modus ponens"
will be used.)

 

SAMPLE: Chris and Nick would be very happy if the Browns beat the
Steelers. The Browns did beat the Steelers, so Chris and Nick are very
happy, indeed.

 

Valid Modus Ponens (Affirming the Antecedent)

 

11.   Madeline must have known the material for the test, because if a
person knows the material, that person will get an A, and Madeline was
one of the students that got an A.

Invalid Affirming the Consequent



Anastasia believes that if she treats people honestly and with an open
mind, she will have diverse friendships. She is honest and open-minded
and has friends all over the world.

Valid Modus Ponens (Affirming the Antecedent)



Roberto thought that if he worked very hard, his boss would give him a
raise or a promotion. He made sure she noticed him, but she did not give
him a raise or promotion. He thought he must not have worked hard
enough.

Valid Denying the Consequent



"I'm still eating too much ice cream," lamented George. "My waist
measurement is the same as it was six months ago. I know if I didn't eat
so much ice cream, I would reduce my waist size."

Valid Denying the Consequent

 

 

The best way to make sure we pay fewer taxes is to elect conservatives.
We must not have elected enough conservatives, because we are paying
more taxes.

Invalid Denying the Antecedent

 

If my neighbor were a decent human being, he wouldn't let his yard trash
fall onto my property. But he's not a decent human being, so we get to
clean his trash as well as ours.

Invalid Denying the Antecedent

 

We'll have fun and learn a lot in this course, if we have great
facilitator. We do have a great facilitator; therefore we are learning a
lot and having fun doing it!

Valid Modus Ponens Affirming the Antecedent

 

If I could understand the concept of hypothetical syllogisms, I would
get a passing grade. Hurray! I got a passing grade, so I must have
understood the concept of hypothetical syllogisms.

Invalid Affirming the Consequent