A post that probably would have been better off unconceived

I thought I'd just come up with an original argument against skepticism about other minds that did not depend on externalism. Excitedly, I began to explain it here. Turns out, I was just wrong. Or maybe not. Anyone have a conceptual analysis for argument handy? In particular, is it possible to have an argument for x with some combination of: (i) unsound, (ii) invalid, (iii) does not end in "x"? In happier news, I found a new toy. But in what sense could a computer program generate a "random prime number"? Time to go home, eat dinner, and read Reid.