Here, then, is a revised version of Marshall's rules: (1) Figure out what you think about an issue, working back and forth among verbal intuition, evidence, and as much math as you need. (2) Stay with it till you are done. (3) Publish the intuition, the math, and the evidence - all three - in an economics journal. (4) But also try to find a way of expressing the idea without the formal apparatus. (5) If you can, publish that where it can do the world some good.

So the story of the baby-sitting co-op is not a mere amusement. If people would only take it seriously—if they could only understand that when great economic issues are at stake, whimsical parables are not a waste of time but the key to enlightenment—it is a story that could save the world.

Now I’m not saying that Keynes was right about everything, that we should treat The General Theory as a sort of secular bible - the way that Marxists treat Das Kapital. But the essential truth of Keynes’s big idea - that even the most productive economy can fail if consumers and investors spend too little, that the pursuit of sound money and s is sometimes (not always!) folly rather than wisdom - is as evident in today’s world as it was in the 1930s. And in these dangerous days, we ignore or reject that idea at the world economy’s peril.

There is nothing that plays worse in our culture than seeming to be the stodgy defender of old ideas, no matter how true those ideas may be. Luckily, at this point the orthodoxy of the academic economists is very much a minority position among intellectuals in general; one can seem to be a courageous maverick, boldly challenging the powers that be, by reciting the contents of a standard textbook. It has worked for me!

The idea of comparative advantage—with its implication that trade between two nations normally raises the real incomes of both—is, like evolution via natural selection, a concept that seems simple and compelling to those who understand it. Yet anyone who becomes involved in discussions of beyond the narrow circle of academic economists quickly realizes that it must be, in some sense, a very difficult concept indeed.

If economists ruled the world, there would be no need for a World Trade Organization. The economist's case for free trade is essentially a unilateral case—that is, it says that a country serves its own interests by pursuing free trade regardless of what other countries may do.

But the honest truth is that what drives me as an economist is that economics is fun. I think I understand why so many people think that economics is a boring subject, but they are wrong. On the contrary, there is hardly anything I know that is as exciting as finding that the great events that move history, the forces that determine the destiny of empires and the fate of kings, can sometimes be explained, predicted, or even controlled by a few symbols on a printed page. We all want power, we all want success, but the ultimate reward is the simple joy of understanding.

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.

In the course of describing my formative moment in 1978, I have already implicitly given my four basic rules for research. Let me now state them explicitly, then explain. Here are the rules: 1. Listen to the Gentiles
2. Question the question
3. Dare to be silly
4. Simplify, simplify