STUDY
GUIDES:
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TEST 2
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TEST 3
Chapter: 1 |
4 |
5 |
6
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STUDY GUIDE - Logic Test 1
WHAT YOU NEED TO KNOW
See
the
study guide
for how to study
DEFINITIONS:
1. Argument: a group of statements where the premisses claim
to provide evidence for the conclusion. There can only be
one conclusion, but there can be one or more premisses.
2. Proposition: a statement or sentence that is true or
false.
3. Premisse: a statement that claims to provide evidence for
the conclusion of an argument
4.
Valid Argument: A deductive argument where if the premisses
are true, then the conclusion is necessarily true.
5.
Invalid Argument: a deductive argument where it is possible
to have all true premisses and a false conclusion.
6. Sound Argument: A valid deductive argument with all true
premisses.
QUESTIONS - Answer (Yes of No) or (True or False):
1.
Can a valid argument have false premisses? YES
2.
Can a valid argument have a false conclusion? YES
3. If an argument is valid, and it has all true premisses,
can the conclusion be false? NO
4. A
sound argument is both valid and has all true premisses.
TRUE
5. If an argument is sound, then the conclusion is true.
TRUE
6. A
valid argument can have all true premisses and a false
conclusion. FALSE
7. If
an argument is invalid, then it is possible for it to have
all true premisses and a false conclusion. TRUE
8.
No invalid argument is sound. TRUE
9.
A valid argument cannot have a false conclusion and all true
premisses. TRUE
10. If a valid argument has a false conclusion, it must
have a false premiss. TRUE
11.
Premisses are statements that are true or false. TRUE
COUNTEREXAMPLE METHOD
INSTRUCTIONS:
Use the counterexample method to prove the following
arguments are invalid. Follow these steps:
1. Rewrite each premiss and conclusion with the form words,
and leave the terms blank.
2. Decide what letters to use for the terms, and put those
letters in the blanks. Be consistent!
3. Recopy step 2. You should have only the form words, and
large blanks where the terms go.
4. Decide on terms that make the conclusion false, and write
them in the blanks.
Try:
cats, dogs, fish, mammals, and animals.
5. Consistently put the conclusion terms where they belong
in the premisses.
6. Decide on terms that will make all the premisses true, and
put them where they belong.
7. Ask yourself: are all the premisses true, and the
conclusion false? If the answer is yes, then you have proven
that the argument is invalid. You’re done. If the answer is
no, then start over again.
Note that the test will provide the arguments in their
proper form. You don’t have to decide what the conclusion or
premisses are.
EXAMPLE:
All dogs are canines.
No
dogs are felines.
No felines are canines.
Step
1:
All are .
No are .
No are .
Step
2:
All D
are C.
No
D are F.
No F
are C.
Step
3:
All are .
No are .
No are .
Step
4:
All are .
No are .
No
Felines are Animals .
Step
5:
All are Animals .
No are Felines .
No
Felines are Animals .
Step
6:
All
Dogs are Animals.
No
Dogs are Felines.
No
Felines are Animals.
Step
7:
All
Dogs are Animals. T
No
Dogs are Felines. T
No Felines are Animals. F
You have proven the argument invalid. You’re done
PRACTICE EXAMPLES
1. All
felines are animals.
All felines are cats.
All cats are animals.
3. All professors are teachers. (mine)
All professors are educated.
All teachers are educated.
4.
Some vertebrates are cold-blooded.
All frogs are vertebrates.
All frogs are cold-blooded.
5. All
canines are dogs.
No cats are canines.
No
cats are dogs.
6. No Puppies are Men.
Some girls are not Men.
Some girls are not Puppies.
7.
Some iguanas are lizards.
Some Snakes are not iguanas.
Some Snakes are not lizards.
8. No Coptics are Shinto.
No Shinto are Hasidic.
No Hasidic are Coptics.
10.
All auditors are investigators.
No auditors are corporate directors.
No corporate directors are investigators.
11. If the doorbell is ringing, then someone is at the door.
It not the case that the doorbell is ringing.
It not the case that someone is at the door.
13.
All dogs are mammals.
All cats are mammals.
All tigers are cats
14. All Presidents are White House dwellers.
Barack Obama is a White House dweller.
Barack Obama is President.
15.
All puppies are dogs.
Some dogs are canines.
Some canines are puppies.
16. Some men are not educated.
All teachers are educated.
Some teachers are not men.
17.
Some tigers are feline.
Some cats are tigers.
Some cats are feline.
18.
Some students are not logicians. (mine)
Some teachers are not logicians.
Some teachers are not students.
19.
Some mammals are felines.
All cats are mammals.
All cats are felines.
20. No
doctors are plants.
No chairs are doctors.
No chairs are plants.
21.
Some artists are not painters.
Some artists are not sculptors.
Some Sculptors are not painters.
22. Some people are lawyers.
Some people are women.
Some women are lawyers.
23.
Some lawyers are not female.
No men are female.
Some men are lawyers.
24. All reformed criminals are regretful.
Some regretful criminals are murderers.
Some murders are regretful.
