Macroeconomics 11th Edition by Michael Parkin

Exercise 4

Use the following news clip to work Problem.
Inflation Should Be Feared
The Fed is trying as hard as it can to spur growth, and to create some inflation. But the Fed must be careful. Inflation remains a danger because U.S. debt is skyrocketing, with no visible plan to pay it back. For the moment, foreigners are buying that debt. But they are buying out of fear that their governments are worse. They are short-term investors, waiting out the storm, not long-term investors confident that the United States will pay back its debts. If their fear passes, or they decide some other haven is safer, watch out. Inflation will come with a vengeance. It's not happening yet: Interest rates are low now. But so were mortgage-backed security rates and Greek government debt rates just a few years ago. But if it happens, it will happen with little warning, the Fed will be powerless to stop it, and it will bring stagnation rather than prosperity.
Explain why the inflation that John Cochrane fears would "bring stagnation rather than prosperity."