Re: Hypothetical syllogisms (conditional arguments)
Posted by adele on 07/28/2005 @ 23:12:47 PST
In Reply to: Re: Hypothetical syllogisms (conditional arguments) posted by adele on 07/28/2005 @ 01:01:11 PST

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: : : : Hypothetical syllogisms (conditional arguments) can
: have
: : : : two valid and two invalid structures. The two valid
: : : : structures are affirming the antecedent (modus
ponens)
: : and
: : : : denying the consequent (modus tollens). The two
: invalid
: : : : structures, or fallacies, are denying the antecedent
: and
: : : : affirming the consequent. Determine if the arguments
: : below
: : : : are valid or invalid and what form they take. The
: first
: : : one
: : : : has been done for you.
: : : : (NOTE: The term "modus pollens" has been used in
some
: : : texts
: : : : as a version of "modus ponens." For the purposes of
: this
: : : : exercise, "modus ponens" will be used.)
: : : :
: : : : SAMPLE: Chris and Nick would be very happy if the
: Browns
: : : : beat the Steelers. The Browns did beat the Steelers,
: so
: : : : Chris and Nick are very happy, indeed.
: : : :
: : : : Valid Modus Ponens (Affirming the Antecedent)
: : : :
: : : :
: : : : 11. Madeline must have known the material for the
: : test,
: : : : because if a person knows the material, that person
: will
: : : : always get an A, and Madeline was one of the
students
: : that
: : : : got an A.
: : : :
: : : : Valid Modius Ponens (Affirming the Antecedent)
: : : :
: : : : 12. Anastasia believes that if she treats people
: : : honestly
: : : : and with an open mind, she will have diverse
: : friendships.
: : : : She is honest and open-minded and has friends all
over
: : the
: : : : world.
: : : :
: : : : Valid Modus Ponens (Affirming the Antecedent)
: : : :
: : : : 13. Roberto thought that if he worked very hard,
his
: : : boss
: : : : would give him a raise or a promotion. He made sure
: she
: : : : noticed him, but she did not give him a raise or
: : : promotion.
: : : : He thought he must not have worked hard enough.
: : : :
: : : : Valid Modus Tollens (denying the consequent)
: : : :
: : : : 14. "I'm still eating too much ice cream,"
lamented
: : : : George. "My waist measurement is the same as it was
: six
: : : : months ago. I know if I didn't eat so much ice
cream,
: I
: : : : would reduce my waist size."
: : : :
: : : : INVALID Modus Tollens (denying the
: consequent)
: : : :
: : : : 15. The good way to make sure we pay fewer taxes
is
: to
: : : : elect conservatives. We must not have elected enough
: : : : conservatives, because we are paying more taxes.
: : : :
: : : : INVALID MOdus Tollens (denying the
: consequent)
: : : :
: : : : 16. If my neighbor were a decent human being, he
: : : wouldn't
: : : : let his tree leaves fall onto my property. But he's
: not
: : a
: : : : decent human being, so we get to clean his tree
leaves
: : as
: : : : well as ours.
: : : : Invalid Modus Tollens
: : : :
: : : :
: : : : 17. We'll have fun and learn a lot in this course,
: if
: : we
: : : : have great facilitator. We do have a great
: facilitator;
: : : : therefore we are learning a lot and having fun doing
: it!
: : : :
: : : : Valid Modus Ponens (Affirming the Antecedent)
: : : :
: : : : 18. If I could only understand the concept of
: : : : hypothetical syllogisms, I would get an A in class.
: : : Hurray!
: : : : I got an A in class, so I must have understood the
: : concept
: : : : of hypothetical syllogisms.
: : Valid Modus Ponens

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