Steve Kates,

First of all, I do not think that introducing explicitly AS and AD is all 
that Keynes did.  But, I accept that he may
well be credited with having done that, and I think that is worthwhile, even 
if you do not.

Regarding the Great Depression, I am more on your side than most are 
regarding the role of the Smoot-Hawley
tariff.  I can also see that this might be argued to be at least somewhat, 
if not entirely, a supply-side phenomenon.
However, it is clearly not all that was going on, and you do not claim that 
it was.

Your other factor is rising interest rates, which I would agree with, 
although I would add the further subsequent
collapse of financial markets more generally, which was not entirely due to 
the rise in interest rates.  However,
the question that arises here is whether or not this is a matter strictly of 
aggregate supply or not.  You make much
of the issue of whether effects are coming from investment or consumption 
and somehow argue that the first have
nothing to do with AD.  But, while investment eventually leads to a change 
in AS the capital stock increases,
the process of building capital stock, the act of real capital investment, 
involves demand for the machinery and
construction and so forth that is involved.  It is a parrt of AD just as 
much as G or X or C are.  Keynes clearly
emphasized fluctuations of I as key to AD fluctuations leading to macro 
fluctuations.  He did not write or speak
of "business hitting the limit of what can be profitably invested."  No, he 
emphasized fundamental uncertainty and
irrationality, with ultimately psychological factors playing the key role, 
"animal spirits," which lie behind the willingness
of business people to carry out capital investments.  If their animal 
spirits collapse, perhaps inspired by a collapse
of the financial sector, then their reduced capital investments reduce AD 
leading to negative multiplier effects that
operate through consumption, and so forth.  So, I do not see your argument 
as at all disproving the role of AD
in bringing about the Great Depression or showing Keynes's analysis to be 
incorrect.

Regarding the role of fiscal policy, I note that content of it matters. 
Thus, some public works are actually
public capital infrastructure that can improve the future productivity of 
the economy, e.g. the autobahnen of
Germany.  Assuredly there are make-work and pork barrel infrastructure 
spending projects that rare wasteful.
But some of this kind of spending is actually capital investment in a real 
sense, even if we do not count it as such
in the official income and product accounts used in most market capitalist 
economies.  Just as with private capital
investment, such spending will have the dual aspect of stimulating AD in the 
short run while shifting out AS in the
longer run, at least from the perspective of us who think that thinking in 
terms of AS and AD is not a complete
absurdity and waste of time and intellectual effort.

Finally, I am glad that you do indeed recognize that Say did not always 
fully accept his own law, as he did allow
for the possibility of hoarding.  You note this by dismissing Say for his 
supposedly inferior awareness of the glorious
truth of his own law.

Of cause the person who really crystallized and publicized his law was not 
John Stuart Mill, but his father, James,
who coined the term "supply creates its own demand," just to get back to the 
HET aspect of this.  Ricardo got it
from him and even called it "Mill's Law" at some point or other.  You may be 
right that the term "Say's Law" did not
appear until the 1920s, but I simply do not know about that one way or the 
other.  Of course J.S. Mill followed
his father and vigorously denied the possibility of "general gluts," 
ascribing recessions most often to financial
collapses often following speculative bubbles.  Now, I have discussed above 
how financial collapses can easily
be analyzed as a source of collapsing aggregate demand as businesses fail to 
carry out real capital investments, which
then, well, I shall not repeat what I said above.  In any case, Mill's 
argument ultimately was one about the long-run,
but clearly in the short run there could be these disruptions of capital 
investment that a Keynesian could easily
trace out as bringing about the recession (in the short run) due to 
insufficient AD.

Besides Malthus, other classical economists who accepted the idea of the 
possibility of a "general glut" were
Sismondi as early as 1819, and Marx, who in Volume III of Capital 
specifically criticized the argument of J.S. Mill.

Barkley Rosser