While I wait for my new friend to show up, I figured I'd take the opportunity to define a few terms that I think were causing hangups in our discussion.
The one that drove me nuts (maybe because of my background) was savings. Typically, we define savings as the residual of income after paying all expenses. This seems consistent with Keynes (Y=C+S or something) and Friedman, who had the "lifetime wealth" formulation. This makes sense to me, but then I'm trained to think in a certain way. I'm open(ish) to debate on this issue.
The other thing is aggregate demand. This is my bad. I always think AD means consumer spending. But it does include investment and government spending and net exports (I imagine). So I promise to keep that in mind.
Any suggestions as to what else to include?