The second is that the story you’ve heard about Greece — that it borrowed too much, and its excessive debt led to the current crisis — is seriously incomplete. Greece did indeed run up too much debt (with a lot of help from irresponsible lenders). But its debt, while high, wasn’t that high by historical standards. What turned Greek debt troubles into catastrophe was Greece’s inability, thanks to the euro, to do what countries with large debts usually do: impose fiscal austerity, yes, but offset it with easy money.

Consider Greece’s situation at the end of 2009, when its debt crisis burst into the open. At that point Greek government debt was near 130 percent of gross domestic product, which is definitely a big number. But it’s by no means unprecedented. As it happens, Greece’s debt ratio in 2009 was about the same as America’s in 1946, just after the war. And Britain’s debt ratio in 1946 was twice as high.

Today, however, Greek debt is over 170 percent of G.D.P. and still rising. Is that because Greece just kept on borrowing? Actually, no — Greek debt is up only 6 percent since 2009, although that’s partly because it received some debt relief in 2012. The main point, however, is that the ratio of debt to G.D.P. is up because G.D.P. is down by more than 20 percent. And why is GDP down? Largely because of the austerity measures Greece’s creditors forced it to impose.