SOME great economists are Aristotelians, discerning the logic of markets from tangible examples around them. Others are Platonists, using their powers of reasoning to grasp ideal economic forms, of which actually existing markets are but flickering shadows. Kenneth Arrow, who died on February 21st aged 95, was both. His ideas gave economics some of its most compelling abstractions and most fruitful applications.
The abstractions won him the Nobel prize at the age of 51. (He remains the youngest winner and the most cited by others in their prize lectures.) He established the conditions under which prices might successfully co-ordinate production and exchange, eliminating shortages and surpluses. Adam Smith provided the best metaphor for this underappreciated feat: the “invisible hand”, guiding resources to their best uses. Ken Arrow and his co-author, Gérard Debreu, provided the best algebra.
To economists versed in mathematics, a well co-ordinated economy is like a system of simultaneous equations, which all hold true at the same time. The solution to these equations is a set of prices that equates demand and supply for scarce…
The Economist: Finance and economics
