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Flashcards in Validity or Probability Deck (8)
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1
Q

Test for Validity

A

Assuming that the premises are true, is it possible for the conclusion to be false? If it is then the arguement is invalid.

2
Q

Test for Probability

A

Assuming the premises are true, what degree of probability would they confer upon the conclusion?

3
Q

A valid argument must have a true conclusion

A

FALSE: A valid argument must have a true conclusion only if all of the premises are true. So it is possible for a valid argument to have a false conclusion as long as at least one premise is false.

4
Q

A sound argument must have a true conclusion.

A

TRUE: If an argument is sound, then it is valid and has all true premises.

5
Q

If a valid argument has a false conclusion, then at least one premise must be false.

A

TRUE: A valid argument cannot have all true premises and a false conclusion. So if a valid argument does have a false conclusion, it cannot have all true premises. Thus at least one premise must be false.

6
Q

If an invalid argument has all true premises, then the conclusion must be false

A

FALSE: It is possible for an invalid argument to have all true premises and a true conclusion.
P1: All dogs are mammals
P2: All terriers are mammal
C: All terriers are dogs.

7
Q

If an argument has all true premises and a true conclusion, then it is valid.

A

FALSE: It is possible for an argument to have all true premises and a true conclusion but still be invalid. See above (#4).

8
Q

If an argument has all true premises and a false conclusion, then it is invalid.

A

TRUE: A valid argument cannot possibly have all true premises and a false conclusion. So the argument is invalid.