It is too early to say there is a consensus about how all these topics fit together. Yet one can say that the new classical challenge has been met: K… - Greg Mankiw

Economics is a young science, and there is still much to be learned. Economists sometimes disagree because they have different hunches about the validity of alternative theories or about the size of important parameters that measure how economic variables are related.

After more than a quarter-century as a professional economist, I have a confession to make: There is a lot I don’t know about the economy. Indeed, the area of economics where I have devoted most of my energy and attention — the ups and downs of the business cycle — is where I find myself most often confronting important questions without obvious answers.

Which brings us to a third group of macroeconomists: those who fall into neither the pro- nor the anti-Keynes camp. I count myself among the ambivalent. We credit both sides with making legitimate points, yet we watch with incredulity as the combatants take their enthusiasm or detestation too far. Keynes was a creative thinker and keen observer of economic events, but he left us with more hard questions than compelling answers.