"No person who cries is a person who can be trusted.Fred is a logic professor.No untrustworthy person is a logic professor.Therefore, Fred does not cry." To tell if this argument is valid, we must:
A)choose the relevant premises for deriving the conclusion and test the resulting syllogism for validity.The other premises are not relevant and need not be tested.
B)first derive the conclusion "some logic professors do not cry" and test that syllogism for validity.
C)first derive the conclusion "Fred is a trustworthy person" and test that syl- logism for validity.Then test a second syllogism which has that conclusion as a premise.
D)do nothing, since this argument is illogical.The conclusion cannot be derived from what is given.

Question

Quizplus · Accepted Answer

The argument's validity can be tested by first deriving the conclusion that Fred is a trustworthy person (since no untrustworthy person is a logic professor and Fred is a logic professor), and then using that conclusion to test a second syllogism which concludes that Fred does not cry (since no person who cries can be trusted). This two-step process checks the logical flow from premises to the final conclusion.

"No Person Who Cries Is a Person Who Can Be