The 2010 TIME 100

The Argumentative Indian is the title of one of Amartya Sen's most recent books. It is also how he thinks of himself. Woe betide the young upstart who ventures to take him on, particularly if the subject is economics or philosophy. Even at 76, Sen, a Harvard professor, still smiles as he demolishes his interlocutor. I speak from experience.

Born in West Bengal, India, he has a patrician style: occasionally loquacious, often ironic, usually genial, always brilliant. Crucially, at the other, older Cambridge, Sen studied philosophy and economics. He has always concerned himself as much with moral as material problems. In his most famous book, Poverty and Famines — inspired by the Bengal famine of 1943, which he witnessed as a boy — he asked how people could starve when food was available. The answer was that the poor simply lacked the capability to buy it. On these and other issues, the argumentative Indian has persuaded. His notion of measuring human development is now central to the work of the U.N. and the World Bank. As a result, Sen's influence extends all the way down to what another great economist has called "the bottom billion."

Ferguson is the Laurence A. Tisch Professor of History at Harvard University and William Ziegler Professor of Business Administration at Harvard Business School

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