The approach described may seem offputting

Paul Samuelson has been, you know, one of the most influential scientists of the 20th century. For the general public, cultivated, this influence was his famous manual, by his role of mentor to the Councillors of the democratic Presidents, and his debates with Milton Friedman in the columns of "Newsweek". For us, economists, it is the inventor of an extraordinarily fertile analytical method which disappears.

Samuelson soon announced what would be its fundamental scientific contribution. His first book, "foundations of economic analysis" (1947) opens with a quote from mathematician e. h. Moore: "the existence of similarities between the central aspects of different theories indicates that a general theory must underlie these various theories and unify them."A little lower, Samuelson cites some of the areas of the economy that it applies to unite: "the economy of production, the theory of the consumer, trade, public finance, theory of cycles, the determination of national income.All of this in what was essentially his doctoral thesis... Theorems precise consequences

It is in this spirit that Samuelson is interested for example in the theory of public goods. How many resources should be devoted to research, national defence, or to the fight against climate change We can explain without using a single symbol the general formula discovered by Samuelson in 1954; but should we give up to clarify the precise conditions which ensure its validity, as well as intimate relationship with the other economic theories. It is one of the lessons that Samuelson learned us: good economic analysis, even applied through mathematical modeling; only formalizing it implies to truly understanding of both the General principles and limits. Another Nobel Prize, Paul Krugman, explains very well in "development, geography, and economic Theory": "we use simplifying assumptions of obviously contrary to the reality, which allow us to bring it back to something that we can manipulate. Our simplifications are dictated in part by intuitions about what is empirically important, and in part by our scope modeling techniques. And finally, if our model is a good model, it helps us to clarify the true system, whose complexity is much greater.

Since the beginning of the current crisis, it is thus often say that economists would be left to seduce, because their mathematical elegance, models that do not leave enough room for the "animal spirits" economic agents. Without prejudging the conclusions of this debate, note that in follower of Keynes Samuelson was familiar with the limits of the rationality of stakeholders in the financial markets. But it would have surely pointed out that if we are advocating new modes of regulating markets, need to begin by returning to the kind of patient, deep and formalized work he gave the example.

The method retains its value: we must think about the functioning of the economic system, reduce the complexity of reality in order to analyze it and find some theorems that illuminate it, return to the real him confronting these new intuitions. And start the cycle, because this return to the real will surely indicate us how we can still improve our model.

The approach described may seem off-putting. But among the best scientists, the rigour of analysis is accompanied by a tireless curiosity. Welcome Paul Samuelson in his University, it was exposure to a fire rolling of questions on history, geography, or the local economy. And curiosity is never extinguished: in quatre-vingt-quatorze years, he participated again in recent months to debated on the origins of the crisis and remedies that can provide. Our colleague from Princeton, Avinash Dixit, put it best: "If I have the chance to find one day Paul Samuelson in heaven, I hope that it will still accept let me attend its course."