In reality, it's a stretch to try to make Krugman into some kind of Friedman-like apologist for QE. But then, you'd have to have actually know something about Friedman to know that.

Look, this isn't hard. We can use the Internet find out what Friedman actually thought about QE. And what he thought was that QE could cure a depression (not that the depression itself was the cure, like Paul does). Indeed, here's what Friedman and co-author Anna Schwartz wrote about the Great Depression in their opus, A Monetary History of the United States, 1867-1960:

Measures that might have been adequate to cope with the earlier [crises] would have been inadequate for the later ones. On the other hand, as we shall see, the bond purchases actually made in the spring and summer of 1932, which did halt the decline in the stock of money but were inadequate to prevent a substantial relapse some months after, would have been more than adequate to cope with the earlier crises.

In other words, Friedman thought the Fed could have kept the Great Depression from being quite so great if it had tried QE sooner. This gets at Friedman's two, related critiques of the 1930s-era Fed: it let the banks fail, and it let the money supply fall. Now, it is true, as Paul points out, that Friedman argued that the pre-Fed bank clearinghouses did a better job managing crises than the Fed did during the depression. (A low bar, to be sure). But Friedman was a pragmatist who recognized that you fight panics with the financial system you have -- so the question was what the Fed could have done.

Plenty, Friedman answered. For one, it could have taken its lender-of-last-resort responsibilities seriously, and stopped runs from forcing otherwise healthy banks into collapse. (But that would have been a bit tricky politically, since half of all banks weren't part of the Federal Reserve System back then). For another, it could have bought bonds, and kept buying them, until the money supply started increasing again. It's mostly forgotten now, but the Fed did half-heartedly try this -- that is, QE -- in 1932 to try to preempt Congress from making it do more. That bond-buying is what Friedman was talking about above, and, as you can see, his only problem with it was that it wasn't tried earlier.

And then there's Japan. As I pointed out before, Friedman thought QE was the answer to its lost decade, too. That's what he said in 1998, and what he repeated in 2000, as you can see below:

Now, the Bank of Japan's argument is, "Oh well, we've got the interest rate down to zero; what more can we do?" It's very simple. They can buy long-term government securities, and they can keep buying them and providing high-powered money until the high-powered money starts getting the economy in an expansion.

Now, in retrospect, Friedman was too sanguine about what QE could do. It's not enough to just increase the money supply. The increase has to be permanent. Nor is it enough to just say it will be permanent. People have to believe it will be permanent. And that's not easy for an independent central bank to do. As Paul Krugman put it back in 1998, a central bank has to "credibly promise to be irresponsible" if it wants to increase inflation. But central banks are nothing if not responsible nowadays, and have trouble convincing us otherwise. They -- and we -- have become the victims of their inflation-fighting success now that a little more inflation is what we need.