Lesson test: Arguments, validity and form

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Arguments, validity and form

1.[2p]
An argument is valid when

there is no possible situation in which every premise is true and the conclusion is false

Correct

every premise is true

The answer is: there is no possible situation in which every premise is true and the conclusion is false

the conclusion is true

The answer is: there is no possible situation in which every premise is true and the conclusion is false

the premises make the conclusion likely

The answer is: there is no possible situation in which every premise is true and the conclusion is false

2.[1p]
A valid argument can have false premises and a true conclusion.

True

Correct

False

The answer is: True

3.[2p]
Which combination is impossible for a valid argument?

True premises and a false conclusion

Correct

False premises and a true conclusion

The answer is: True premises and a false conclusion

False premises and a false conclusion

The answer is: True premises and a false conclusion

True premises and a true conclusion

The answer is: True premises and a false conclusion

4.[2p]
Name the form: if $P$ then $Q$ ; not $Q$ ; therefore not $P$ .

CorrectNot quite: modus tollens

5.[3p]
Which of these argument forms are valid?

Select all that apply

If $P$ then $Q$ ; $P$ ; therefore $Q$

Correct

If $P$ then $Q$ ; not $Q$ ; therefore not $P$

Correct

If $P$ then $Q$ ; $Q$ ; therefore $P$

The answer is: If $P$ then $Q$; $P$; therefore $Q$, If $P$ then $Q$; not $Q$; therefore not $P$

If $P$ then $Q$ ; not $P$ ; therefore not $Q$

The answer is: If $P$ then $Q$; $P$; therefore $Q$, If $P$ then $Q$; not $Q$; therefore not $P$

6.[3p]
"If the drug works, the patients improve. The patients improved. So the drug works." What is wrong with this?

It affirms the consequent, and improvement could have other causes

Correct

It denies the antecedent

The answer is: It affirms the consequent, and improvement could have other causes

Its premises contradict each other

The answer is: It affirms the consequent, and improvement could have other causes

Nothing: it is valid but unsound

The answer is: It affirms the consequent, and improvement could have other causes

7.[3p]
Match each form to whether it is valid or invalid.

Modus ponens
Modus tollens
Affirming the consequent
Denying the antecedent
Disjunctive syllogism

valid
valid
valid
invalid
invalid

Show the answer

Modus ponens: valid Modus tollens: valid Affirming the consequent: invalid Denying the antecedent: invalid Disjunctive syllogism: valid

8.[3p]
What does refutation by parallel form show?

That the argument is invalid, because a same-shaped argument has true premises and a false conclusion

Correct

That the argument's premises are false

The answer is: That the argument is invalid, because a same-shaped argument has true premises and a false conclusion

That the conclusion is false

The answer is: That the argument is invalid, because a same-shaped argument has true premises and a false conclusion

That the argument is unsound but still valid

The answer is: That the argument is invalid, because a same-shaped argument has true premises and a false conclusion

9.[2p]
An argument whose premises contradict each other is valid, whatever its conclusion says.

True

Correct

False

The answer is: True

1.[2p] An argument is valid when

2.[1p] A valid argument can have false premises and a true conclusion.

3.[2p] Which combination is impossible for a valid argument?

4.[2p] Name the form: if P then Q; not Q; therefore not P.

5.[3p] Which of these argument forms are valid?

6.[3p] "If the drug works, the patients improve. The patients improved. So the drug works." What is wrong with this?

7.[3p] Match each form to whether it is valid or invalid.

8.[3p] What does refutation by parallel form show?

9.[2p] An argument whose premises contradict each other is valid, whatever its conclusion says.

1.[2p]
An argument is valid when

2.[1p]
A valid argument can have false premises and a true conclusion.

3.[2p]
Which combination is impossible for a valid argument?

4.[2p]
Name the form: if $P$ then $Q$ ; not $Q$ ; therefore not $P$ .

5.[3p]
Which of these argument forms are valid?

6.[3p]
"If the drug works, the patients improve. The patients improved. So the drug works." What is wrong with this?

7.[3p]
Match each form to whether it is valid or invalid.

8.[3p]
What does refutation by parallel form show?

9.[2p]
An argument whose premises contradict each other is valid, whatever its conclusion says.