You don't have to watch a film on Alexander to see how an impossible arrow can suddenly turn possible. Sometimes all it takes is a Big Idea. In the world of academia, Nobel laureate Amartya Sen has done it by coming up with an idea to turn something called Arrow Impossibility into a distinct possibility.

The idea, actually, is a proposal. A social choice proposal: "the systematic use of interpersonal comparisons of individual well-being" in making collective decisions on behalf of everyone. What has the idea done? It has revived the left-for-dead academic discipline of Welfare Economics by mathematically showing how-if the proposal is accepted-a push for economic efficiency (the traditional Right agenda) need not compromise the quest for social equity (the classic Left agenda). Nor vice-versa.

That's a big breakthrough. For decades, people worried that the Free Market equilibrium results in an 'unfair' division of the pie, but making it fair causes market distortions which reduce the size of the pie. So it was a case of 'either-or', at least by way of priority (since in the long run, whether we crack the riddle of our celluloid time or not, we're all dead). Amartya Sen's idea rekindles the dream of efficiency and equity.

That, admittedly, is an oversimplification of sorts. By the actual Arrow Impossibility theorem, no joint-decision system was said to be possible that could simultaneously satisfy five desirable conditions. Three of them to do with freedom: independence (of irrelevant alternatives), non-dictatorship (no single person enforces his will) and Pareto efficiency (if one person has a preference nobody objects to, it holds for all). And two conditions to do with rationality, too mathematical to elaborate here.

Anyhow, by the theorem, something had to give. All five in harmony? Impossible, they said. Going liberal called for irrationality, and playing Mr Rational needed some whips to be cracked. Forget the boon-curse divide, welfare was doomed, people thought... till Amartya Sen came up with his marvellous possibility, and gave us fresh hope for a Mutually Assured Destiny that could contain and reverse the fissures taking us towards its acronym-sake, Mutually Assured Destruction. That's the power of newly imagined information. And it's sure worth a try.