Krugman against Dan Kervick and the MMTers:

But leaving the debt ceiling on one side, isn’t it true that since spending can currently be financed by Fed money printing, we shouldn’t care at all about the notional debt owed to the Fed? Alas, no. 

It’s true that printing money isn’t at all inflationary under current conditions— that is, with the economy depressed and interest rates up against the zero lower bound. But eventually these conditions will end. At that point, to prevent a sharp rise in inflation the Fed will want to pull back much of the monetary base it created in response to the crisis, which means selling off the Federal debt it bought. So even though right now that debt is just a claim by one more or less governmental agency on another governmental agency, it will eventually turn into debt held by the public. 

We are living in weird economic times, where many of the usual rules don’t apply and there are big free lunches to be had. But not everything is a free lunch, even now. Sorry.