Search All of the Math Forum:
Views expressed in these public forums are not endorsed by
Drexel University or The Math Forum.


YBM
Posts:
804
Registered:
11/27/09


Re: 2.25  The meaning of "implies" in mythmatics.
Posted:
Jul 24, 2014 6:28 AM


Le 24/07/2014 09:09, John Gabriel a écrit : > "If John Gabriel is always right, then John Gabriel is never wrong." > > Suppose that p = John Gabriel is always right and that q = John Gabriel is never wrong. > > Then according to the nonsensical imply truth table: > > ¬p OR q > > Assume p and q are FALSE. > > Then, ¬FALSE OR FALSE = TRUE. > > So, if "John Gabriel is always right" is FALSE (that is, John Gabriel is NOT always right), then *John Gabriel is always right*
No crank, if q is FALSE (John Gabriel is NOT always right) then (p => q) is TRUE (that is "John Gabriel is always right" => "John Gabriel is never wrong"), but this says nothing about truth of q ('John Gabriel is never wrong').
What mysterious reason makes you think that if (p => q) is TRUE, then q is necessarily true?



