# Testing validity

• Oct 31st 2008, 10:48 PM
calltorahat
Testing validity
Hi, This is my first ever post on this fora so a warm Hello to all

my question is:
how will we varify the validity of following argument

john will become Good-Actor or he will not become a Tv-Star.
he will become a Tv-Star.
Therefore he will become a Good-Actor.

yeah, pretty basic, i know, but i am a bit confused while performing its logical steps (newely joined Discrete Mathematics classes).
any help will be appriciated.

respects
rahat
• Nov 1st 2008, 02:44 AM
calltorahat
As for as I understand the solution should be as follows

a = John will become a good actor
s = John will becomea tv star

Premises 1 = john will become Good-Actor or he will not become a Tv-Star.
= a OR ~s

Premises 2 = John will become a Tv-Star.
= s

Conclusiont = Therefore he will become a Good-Actor.
= a

and if we construct a Truth table for it

a l s l ~s l a OR ~s l a
----------------------------------
T l T l F l T l T
----------------------------------
T l F l T l T l T
----------------------------------
F l T l F l F l F
----------------------------------
F l F l T l T l F
----------------------------------

So the argument is valid
• Nov 1st 2008, 06:13 PM
vagabond
( (a \/ ~s) /\ s ) -> a is a tautology (a->a is always true), so it is a valid argument.
• Nov 2nd 2008, 06:03 PM
calltorahat
Quote:

Originally Posted by vagabond
( (a \/ ~s) /\ s ) -> a is a tautology (a->a is always true), so it is a valid argument.

Thanks for the reply vagabond... :)