>Both premise and conclusion cannot be true in your argument. QED.

Exactly. That was the point, to show that a valid argument was unsound, meaning one of Doug's premise was false.

>Thus, an argument is sound if and only if : it is a valid argument, and all the premises are true.
>By contradicting the premise, your argument is both invalid and unsound.

First, an invalid argunment cannot be unsound:
http://www.kcmetro.cc.mo.us/longview/ctac/soundness.htm
Only Deductive , Valid arguments can be sound or unsound.
Sorry.

Second, which of my two arguments contradicts its own premises? Keep in mind I presented two seperate arguments (Modus Ponens) with four different premise and two different conclusions. THe fact that the conclusions contradicted one another means at least one of the arguments is unsound. Which is what I tried to prove. It in no way means that the arguments are invalid.

Whether or not the premises of an argument are true or not has absolutely no impact on the validity of an argument.

>An omnipotent person both can and can't do whatever they like, that's the nature of omnipotence and we humble mortals can't expect to understand it. Prove me wrong. ;-)

This is what it all comes down to doesn't it? "You can't argue about God with human words" *yawn*