Theos-Talk Archives (January 1997 Message tl00702)

The Vietnamese Terror wrote:

>>Mary P.:
>Premise: If A, then B
>Premise: A
>Conclusion: B  
>
>Although there may be all kinds of room for debate about the truth of the
>premises, I see no room for debate about the conclusion, assuming the
>premises are true.  Unless my logic is mistaken, which is always possible,
>if someone concluded something other than B from this syllogism, they would
>have been illogical.
>
>Thoa:
>Let's take A=Johnny trips over the curb, and
>B=Johnny falls
>
>Premise:  If Johnny trips over the curb, then Johnny falls
>Premise:  Johnny trips over the curb
>Conclusion:  Johnny falls
>
>But what if the conclusion is C=Johnny balances himself and does not fall?
>You have left out the C possibility, which could logically happen.

If these premises are true, Johnny could not balance himself and not fall.
C is only possible if one of the premises is false.