(January 6, 2012 at 2:15 am)fr0d0 Wrote: Yeah point one is where it fails.
I believe you're confusing validity with soundness. A sound argument must be valid and have true premises. As a result, a presuppositional argument can only be sound if it's premises can be demonstrated to be true. If the premises were demonstrably true, they wouldn't be found in a presuppositional argument.
In my view, this makes presuppositional arguments an exercise in mental masturbation and not a good tool for determining truth.
Checkmate.