I agree overall in terms of money supply and inflation. While there are various factors, money supply is huge.
In fact I will say I disagree with a majority of economists that the Great Depression was primarily a monetary failure.
I profoundly disagree; I think the Fed could of reduced money supply even further, say up to 4% a year further deflation (!!!!) and had an expanding economy -- at least within 3 years after the stock bubble bursting -- had macroeconomic policy been reasonable.
The reason I say this is there have been many economies, China is almost an example, where inflation has been fairly tame and productivity / real wages have skyrocketed. And even better example is most of the US history (wars excluded) 1776-1900. The US had virtually no inflation yet skyrocketing economic growth.
I disagree that you need money supply growth to encourage and increase economic activity, and I disagree that slow reductions in money supply adversely affect economies (under most conditions). My personal thoughts are that as long as true CPI inflation is within 3% or so either way, and isn't shifting more than about 4% +/- a year, it really doesn't matter (well ideally you'd have 0% true CPI long term averages but that is a minor positive).
I realize I'm not supporting this with much evidence, but I will just say you will occasionally see economies with deflation and very high sustained economic growth and this should be explained. My explanation is as long as inflation is reasonably well contained even slightly negative the answer is that it matter far less than people think.
In some very rare cases (perhaps Japan) inflationary policies in the medium term may be useful but even here you have to be very careful and more data points are needed I believe (and even the Japan case is not a positive one for this theory per se).