One Indian, the old joke goes, is a monologue; two Indians are a debate; three Indians, two political parties. That Indians are argumentative seems beyond dispute. But it takes an economist of Nobel laureate Amartya Sen's standing to convert that proposition into a magisterial book. "The Argumentative Indian" ( 432 pages. Farrar, Straus and Giroux) is a collection of 16 essays--mostly expanded from lectures and previously published articles--that attest to the depth and eclecticism of his intellect. "I've always liked arguing with people," he says from his home in Cambridge, Massachusetts, in between trips to New York and Florence in his dizzyingly peripatetic life.

He can certainly hold his own on any number of topics. Though Sen, 72, won his 1998 Nobel Prize in Economics and has taught the subject at both Harvard and Cambridge, he could just as convincingly be described as a sociologist, historian, Sanskritist, political analyst and moral philosopher--for starters--as his new book makes clear. "I first wanted to be a physicist," says Sen, "but my political interests led me to economics."

That path began, appropriately enough, with Sen's birth on the campus of Vishwa-Bharati University, founded by the great Nobel laureate in literature Rabindranath Tagore in the West Bengal village of Shantiniketan. It was Tagore who prophetically chose the name Amartya--or "immortal"--for the only other Bengali who would go on to win the Nobel Prize. Two things moved Sen deeply as a child: the Great Bengal Famine of 1943, which killed thousands, and the religious violence that accompanied the partition of India in 1947. The teenage Amartya saw a bleeding Muslim laborer stumble into his Hindu family's home after being knifed in a communal riot; the man had ventured into the "wrong" neighborhood looking for work to feed his family. Economics, politics and morality intersected in those episodes, indelibly marking Sen's growing mind.

Initially, like virtually every Kolkata collegian, Sen's politics were leftist, but over time they were leavened by an abiding faith in freedom and an interest in philosophy. His pioneering work in welfare economics and social-choice theory--how a society's wishes can be aggregated from the diverse views of its members--was cited by the Nobel committee. But he has become known to a wider audience for his work on famines, particularly the proposition that there has never been a famine in a functioning democracy. His theory of "development as freedom" argues compellingly that it is more important to be free than to be rich, and that different kinds of freedom--political, economic and social--strengthen each other.

No one is more surprised by his growing influence than Sen himself. "I opened The New York Times last Sunday and found a full-page ad featuring Laura Bush and Hillary Clinton, with a headline quoting me!" he says. "I was pleased to see it was on the importance of women's education." Sen's concern for the impoverished, undernourished and marginalized, especially women, comes through strongly in his essays. His Nobel Prize money has largely gone to two trusts he founded, one each in India and Bangladesh, focusing on education and health care for the poor.

His latest book goes beyond economic theorizing to look at the pluralist heritage of India. It is a powerfully constructed case for his homeland's political and cultural heterogeneity, and of the "reach of reason" in India's intellectual traditions. "It's something which has been in my mind for a while," Sen says. "I've been very involved with India throughout my life, I've remained an Indian citizen, spent 11 years studying ancient texts in Sanskrit." But he had never before sat down to pull together his thoughts about India into one book.

Sen is particularly critical of the Western overemphasis on India's religiosity at the expense of any recognition of the country's equally impressive rationalist, scientific, mathematical and secular heritage. The son of a professor of soil chemistry, he vividly recalls going to the lab with his father, "testing hypotheses, seeing whether experiments worked out or not." That "scientific spirit of inquiry," he says, can also be seen in ancient India. His book cites 3,500-year-old verses from the Vedas that speculate skeptically about creation, and details India's contributions to the world of science, rationality and plural discourse--fields generally treated by Orientalists as "Western spheres of success."

But he reserves plenty of criticism for India's homegrown radical Hindu fundamentalists. "My view of India is of a very broad civilization, which I've seen being miniaturized by sectarians," he says, alluding to the Hindutva ("Hindu-ness") movement that has sought to promote a strictly Hindu identity for India. Sen's book attacks such a "narrow and bellicose" interpretation, while reaffirming his own "capacious idea of India" as an authentically plural and tolerant civilization. "One of the points of my retaining my Indian citizenship is to be able to participate in Indian political discussions," says Sen, who since his student days has never been out of India for more than six months at a stretch and manages a visit several times a year.

That sense of passionate engagement with India informs all the essays in "The Argumentative Indian." On Indian democracy, he is both reasoned and critical. While hailing India's success in preventing the famines that occurred with depressing regularity under British colonial rule, he stresses that this does not mean the problem of chronic and endemic hunger ("a much more complex task") has been solved.

Back at Harvard after serving six years as the first non-English master of Trinity College, Cambridge, Sen--film and theater buff, cricket fan, badminton player, devoted power walker and voracious reader--embodies the yearning for eclectic learning. As a young man he translated a number of George Bernard Shaw's plays into Bengali, but mislaid the manuscripts; perhaps they will turn up, he imagines, in his recently deceased mother's trunkfuls of papers. His next book will be on "identity and violence--a cultural and political analysis of terrorism in today's world, on how high theory feeds low politics."

For Sen, who is married to historian Emma Rothschild and has four children from two previous marriages, being Indian and being cosmopolitan are by no means mutually exclusive. He traces his convictions to sources as disparate as Condorcet and Chakravarti and does not consider any one place home. "I feel very at home in Shantiniketan, in Cambridge, Massachusetts, in Cambridge, England, in Italy. If I had to choose one of them and live there only, that I would regard as a very serious loss." One of his essays, on the films of the great director Satyajit Ray, affirms Sen's case for India's absorptive culture. "In our heterogeneity and in our openness lies our pride, not our disgrace," Sen writes. "Satyajit Ray taught us this, and that lesson is profoundly important for India." Not to mention the rest of the world.