Pat Gunning,

Sims's approach is fully atheoretical.  It is one way to go,
but hardly the only one.  His approach is more influential
than it was initially, but it is hardly proof that AD is a
useless anachronism that should not be taught to
students.  Should we spend our time in principles
courses avoiding supply and demand and simply
teaching vector-autoregressive, time-series modeling?

You rather cavalierly dismiss my "casual observation
about pre-war Germany."  Well, I would ask what you
have to say about that?  After all, it was the Great Depression
that inspired Keynes to write the GT, and inspired many
economists to think that studying AD was something
important to do.  Arguably Germany was the most
dramatic example of all nations in the world, with the
deepest plunge and the most rapid turnaround, rather
clearly led by a fiscal policy of what is now often labeled
as a "military Keynesian" sort.  (I used Germany as an
example to stay away from the ongoing debates about
whether it was WW II that got the US out of the GD or not).
So, this is not just some odd, casual example.  It is an
absolutely central example.

If you do not invoke aggregate demand driven by fiscal
policy, then how do you explain how Germany went from
30% unemployment to near zero between 1933 and 1939?
There are other, similar examples, but that one is an especially
clearcut and important one.  Ball is in your court, Pat.

Barkley Rosser