The best you can say about economic policy in this slump is that we have for the most part avoided a full repeat of the Great Depression. I say “for … - Paul Krugman

It’s a tribute to the importance of Friedman’s work that questions about his legacy bear so directly on contemporary policy issues. But for that reason it’s also important not to engage in . Friedman was a great economist, but like every other great economist in history, he was also wrong about some important things.

It is important to realize that even now Fed officials are not quite sure how they pulled this rescue off. At the height of the crisis it seemed entirely possible that cutting interest rates would be entirely ineffectual—after all, if nobody can borrow, what difference does it make what the price would be if they could? And if everyone had believed that the world was coming to an end, their panic might—as in so many other countries—have ended up being a self-fulfilling prophecy. In retrospect Greenspan seemed to have been like a general who rides out in front of his demoralized army waves his sword and shouts encouragement, and somehow turns the tide of battle: well done, but not something you would want to count on working next time.

I do not mean to say that formal economic analysis is worthless, and that anybody's opinion on economic matters is as good as anyone else's. On the contrary! I am a strong believer in the importance of models, which are to our minds what spear-throwers were to stone age arms: they greatly extend the power and range of our insight. In particular, I have no sympathy for those people who criticize the unrealistic simplifications of model-builders, and imagine that they achieve greater sophistication by avoiding stating their assumptions clearly. The point is to realize that economic models are metaphors, not truth. By all means express your thoughts in models, as pretty as possible (more on that below). But always remember that you may have gotten the metaphor wrong, and that someone else with a different metaphor may be seeing something that you are missing.