UQx META101x.1.4.1.2 Validity and Soundness


We looked earlier at how important it is to
have an argument when you want to convince someone of something, how it’s not enough
just to be passionate or forceful. But just because you have an argument, it
doesn’t mean you have a good one. So what makes one argument better than another? How
do we go about evaluating arguments? Recall two important words we learned previously:
SOUND and VALID. A SOUND argument is one in which the PREMISES are true and the argument
is VALID. A VALID argument is one in which the CONCLUSION follows logically from the
PREMISES, so were the premises true — which may or not be the case — then the conclusion
would be. The best argument is one that is sound. Since
it is VALID, were the premises true the conclusion would be. But SOUNDNESS also requires the
premises to be true. So in a SOUND argument the reasons offered support the conclusion
by making it true. It is possible to have an argument, however,
that is valid, but not sound. Here’s an example. DAVE
I’m the most beautiful man in the world. The most beautiful people give the best advice,
therefore I give the best advice! Dave is excited because he thinks the argument
is a good one. It “makes sense” to him because the conclusion really does follow
from the premises. Have a look at the argument again. Sure enough, if the premises are true, the
conclusion does make sense – the argument is VALID. But, sadly for Dave, at least one
of those premises is not true – therefore the argument is not SOUND. Even if an argument is logically well constructed,
it may be a poor one because it is unsound. In this course, we will use the ideas of validity
and soundness to evaluate some of the great arguments in philosophy, as well as some of
the not so great ones…

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