Deck 8: Deductive Arguments

Question 1

Which of the following is an example of a categorical syllogism?

A) "If you take that road, you'll end up lost. So don't take that road."
B) "All men are mortal. Socrates is a man. Therefore, Socrates is mortal."
C) "Every crow I have ever seen is black. Therefore, all crows are black."
D) None of these answers is correct.

Answer 1

B
Explanation: A categorical syllogism is a deductive argument that uses categories in its reasoning. In this particular case, the categories are "man" and "mortal." The argument concludes that Socrates belongs to the category "mortal," since everything that belongs to the category "man" also belongs to the category "mortal" and Socrates belongs to the category "man."

Question 2

Which of the following is a type of deductive argument?

A) an argument by elimination
B) generalization
C) polls
D) an argument by analogy

Answer 2

A
Explanation: An argument by elimination starts with a list of possibilities, eliminates possibilities one by one, and then concludes the last remaining possibility must be true. Such an argument ensures the truth of the conclusion if each premise is true. Consider this simple argument by elimination: "Either John or Bill ate the cookie. John did not eat the cookie. Therefore, Bill ate the cookie."

Question 3

Suppose the conclusion of a valid deductive argument was false.What can you conclude about the argument?

A) The argument is not deductively valid at all!
B) All of the premises are true.
C) All of the premises are false.
D) At least one of the premises is false.

Answer 3

D
Explanation: Since the argument is deductively valid, we know that if all of the premises were true, then its conclusion would be true is well. So we also know that if the conclusion is false, then at least one premise must be false as well. The truth of the premises would have necessitated the truth of the conclusion. Note that deductively valid arguments can have false conclusions. But when they do, it is because at least one of the premises is false as well.

Question 4

Which of the following is a valid deductive form of argument?

A)modus tollens
B)affirming the consequent
C)ad hominem
D)These are all deductively valid forms of argument.

Question 5

Which of the following is a valid categorical syllogism?

A) "Some animals are mammals. John is an animal. Therefore, John is a mammal."
B) "Some animals are mammals. John is a mammal. Therefore, John is an animal."
C) "No animals are plants. John is a mammal. Therefore, John is not a plant."
D) "No animals are plants. John is an animal. Therefore, John is not a plant."

Question 6

Who is Bo Dietl?

A) a highly decorated police officer known for his investigative expertise.
B) the discoverer of an important form of deductive reasoning known as "Dietl's Method".
C) a mathematician who discovered the type of deductive argument known as an argument based on mathematics.
D) None of these answers is correct.

Question 7

Which is true of the following argument: "All dogs are rabid.Some rabid things are mammals.Therefore,some dogs are mammals."

A) The argument is sound.
B) The argument is valid.
C) The argument is both unsound and invalid.
D) None of these answers is correct.

Question 8

Which of the following is a disjunctive syllogism?

A)"Either John,Bill,or Mary stole the diamond.John did not steal it.Mary did not steal it.Therefore,Bill stole it."
B)"If John ate a cookie,then so did Mary.If Mary ate a cookie,then so did Bill.Therefore,if John ate a cookie,then so did Bill."
C)"If you do not give me money,I will kill you."
D)None of these answers is correct.

Question 9

Which of the following is true of deductive arguments?

A) A deductive argument always establishes the truth of its conclusion.
B) Deductive arguments typically contain words and phrases such as "probably" and "it is likely the case."
C) The conclusion of a valid deductive argument necessarily follows from its premises.
D) The premises of a deductive argument are always true.

Question 10

Which of the following is NOT a type of deductive argument?

A) an argument based on mathematics
B) an argument from definition
C) an argument by elimination
D) These are all types of deductive arguments.

Question 11

Which of the following is the primary concern of logic?

A) truth
B) winning arguments
C) validity
D) All of these are equally of concern to logic.

Question 12

Which of the following best describes a hypothetical syllogism?

A)a hypothesis that is confirmed by observation
B)a deductive argument with two premises,at least one of which is a hypothetical claim
C)a generalization about a scientific hypothesis
D)a deductive argument with a conclusion that is a hypothetical claim

Question 13

Which of the following determines whether or not an argument is valid?

A) whether or not all of its premises are true
B) whether or not its conclusion is true
C) the form of the argument
D) All of these answers are things that determine whether an argument is valid.

Question 14

Which of the following best describes a syllogism?

A) an argument with three premises
B) an inductive argument that offers support for its conclusion
C) an argument by analogy such that if its premises are all true, then its conclusion is necessarily true
D) a deductive argument with two premises and a conclusion

Question 15

Which of the following is a sound argument?

A) "If the moon is made of cheese, then Barack Obama is the president of Mexico. The moon is made of cheese. Therefore, Barack Obama is the president of Mexico."
B) "Either Turkey is a country or New York is a country. New York is not a country. So Turkey must be a country."
C) "I have seen millions of black crows. Therefore, all crows must be black".
D) "If the Earth is flat, then John Kerry is president of the United States. The Earth is not flat. Therefore, John Kerry is not president of the United States."

Question 16

Which of the following is true of sound arguments?

A) A sound argument may have a false premise.
B) A sound argument is valid.
C) A sound argument sounds good, but may be invalid.
D) A sound argument always has a true conclusion even if one of the premises is false.

Question 17

Suppose a premise of a valid deductive argument were false.What can you conclude about the conclusion of this argument?

A) The conclusion is true.
B) The conclusion is false.
C) The conclusion is valid.
D) None of these answers is correct.

Question 18

"All dogs are diseased.John is a dog.Therefore,John went to the vet." Which of the following is true of the preceding argument?

A) The argument is false.
B) The argument has a false conclusion because it has at least one false premise.
C) The argument is not deductively valid.
D) The argument is sound.

Question 19

Which of the following is a universal proposition?

A) "Some dogs are mean."
B) "No dogs are purple."
C) "There are three dogs chasing me."
D) None of these answers is correct.

Question 20

"If you went to the store last night,then we have milk.If we have milk,then we can have breakfast.If we have breakfast then we don't have to stop at Dunkin' Donuts.Therefore,if you went to the store last night,we don't have to stop at Dunkin Donuts." The preceding argument is which of the following types of argument?

A) an inductive argument
B) modus ponens
C) chain argument
D) generalization

Question 21

If a valid deductive argument has a true conclusion,then it must have all true premises.

Question 22

Nothing true or false follows from a conditional claim alone.
B." Such claims alone are not arguments, since nothing follows from them alone.

Question 23

A conditional claim cannot be the conclusion of a valid argument.

Question 24

All invalid arguments are unsound.

Question 25

Valid deductive arguments guarantee the truth of their conclusions.

Question 26

All valid arguments are sound.

Question 27

The premise "No tigers are vegetarians" is a negative proposition.

Question 28

The following argument is a sound disjunctive syllogism: "Either the Earth is perfectly flat or the Earth is perfectly round.The Earth is not perfectly flat.Therefore,the Earth is perfectly round."

Question 29

The following argument is valid: "Some dogs are robust.John is robust.Therefore,John is a dog."

Question 30

Arguments by elimination are deductive.

Question 31

Syllogisms are deductive arguments with two premises and a conclusion.

Question 32

The first premise of a categorical syllogism has only one term.

Question 33

A valid deductive argument always has a true conclusion.

Question 34

The following argument is valid: "If the moon is made of cheese,then we can eat the moon.We cannot eat the moon.Therefore,the moon is not made of cheese."

Question 35

All deductive arguments have fewer than four premises.

Question 36

The following argument is valid: "If it is raining outside,then the streets must be wet.The streets are wet.Therefore,it must be raining outside."

Question 37

If an argument contains a premise that is just a definition,then the argument is invalid.

Question 38

Arguments by elimination are a type of disjunctive syllogism.

Question 39

The premise "All dog go to heaven" is a particular proposition.

Question 40

The following argument is valid: "All dogs are robust.All robust things smell.John is a dog.Therefore,John smells."