Fiscal Multipliers in War and in Peace

It truly is breathtaking how certain some people are of what they know to be true about the way a macroeconomy operates. The Krugmans and DeLongs of this world really make it sound like everything we really need to know has been settled long ago. Yes, the science is "settled" (where have we heard this before?).

I recently came across this piece by Brad DeLong: A Guide for the Perplexed. Consider the following quote:

But when fiscal boost was tried on a large enough scale, it certainly did the job. And it is reasonable to infer (with all the caveats provided by the CBO) that what is true in the very large will be true in the merely large as well. Eugene Fama says that it is theoretically impossible for fiscal stimulus to boost output: World War II proves him wrong. Robert Barro says that the multiplier is zero: World War II proves him wrong. Benn Steil says that Jacques Rueff in 1947 conclusively proved that fiscal policy could not boost employment: World War II proves him wrong.

Implication: a WWII style fiscal stimulus will "do the job" in a peacetime recession. WWII "proves" it. Egad...how does he know this? Why do I not feel as confident that this is the case? Am I truly that dense? (an invite to some rather rude comments, I'm sure!)

In any case, I decided to gather my thoughts on the subject and post them here for public review and criticism. The piece is a bit too long for a blog posting; so if you're interested, please click here. Looking forward to any comments.