Walk down a creaky hallway, turn left, and he is there, the slight, salt-and-pepper-haired, 67-year-old man who revolutionized the study of language. The man who, in the process, transformed our understanding of behavior, thinking, and the mind. The man who is compared to Sigmund Freud and Albert Einstein.

That would be enough for most academics. But for the last 30 years, Chomsky has been one of the most prolific, radical, and contrary political commentators in the United States. Adherents of his school of political thought number at least as many as do the apprentices of his linguistic theory; a half-dozen Chomsky Web sites dot the Internet, featuring his latest lectures and essays on politics and society.

Though his latest book on linguistics, published earlier this fall, is being greeted with skepticism by some peers, Chomsky's place in academic history seems secure. It is his legacy as a political commentator that is much less certain.

He is still treated as intellectual royalty in Europe, but at home, his political tracts appear in obscure journals -- never, say, on the op-ed page of The New York Times. This, at a time when his colleagues in academia are calling for more discussion of politics and policy, for the cultivation of a more engaged "public intellectual," at a point in his life when Chomsky should be maturing into a kind of elder statesman among political commentators, and at a time when conservative dominance in Washington cries out for starkly opposing views, for the novelty, if nothing else.

Ask this intellectual radical why he is shunned by the mainstream, and he'll say that established powers have never been able to handle his brand of dissent. But as the twilight of his career begins, his followers are left to wonder: Has Noam Chomsky's time passed? Or is he just hitting his stride? Most weekdays in the academic year, Chomsky can be found in Building 20, and there, on a recent warm afternoon, the talk turns inevitably to politics. Leaning back on a creaky swivel chair, in jeans and sneakers, one foot propped on a desk drawer that he's pulled out for that purpose, he has taken time out from his reading and writing - essays, books, dozens of letters a day -- to consider the congressional Republicans who swept into power in 1994. And in no time, he's worked up a pretty good riff. "I think they're extremely dangerous," he says. "I think they could open the door to American fascism."

It's like Iran in 1980 or Germany in the '30s, he says. The industrialists in Germany backed the fascists, and the merchants in Iran backed the fundamentalists as forces for revolution. "But then," he says, "it turned out these guys had minds of their own."

Same way with the corporate interests that run America, Chomsky says: They're all for the House Republicans cutting back on government regulations and slashing aid to the poor, but CEOs are panicked that some renegades might start chiseling away at government subsidies for business - the money that pours in through the Commerce and Energy departments, and most of all through the Pentagon. "They couldn't survive without that subsidy and never have," he says.

In a moment, he is fuming about former defense secretary Robert McNamara's recent book on Vietnam and all this garbage about why Japan hasn't apologized for the war, when the United States has been responsible for a mountain of crimes against the Vietnamese people and thousands of others in Central America and the Middle East. Take the April Oklahoma City bombing, he says, which resembled nothing so much as a CIA-arranged car-bomb attack outside a Beirut mosque in 1985 that killed 80 innocent people. Is anybody apologizing for that? Anybody even talking about it?

An hour passes, and it is vintage Chomsky: Standing outside the system, deconstructing the propaganda, daring to make the connections that no one else will make. Assessing American politics and policy, both foreign and domestic, Chomsky has perfected a potent formula of detachment, bulletproof logic, and piles of documented evidence behind every assertion.

Yet, for all his diligent analysis, he wasn't the one asked by The New York Review of Books to write about McNamara's apologia. He's never been invited to join a panel up the street, at Harvard's Kennedy School of Government. As a political commentator, he labors in a special kind of isolation, one where the spectre of irrelevancy looms. To understand Chomsky now, one must return to the very beginning, to working-class Philadelphia just before the Depression, where Avram Noam Chomsky was born on December 7, 1928. He was the son of William and Elsie (Simonofsky) Chomsky, both Hebrew teachers and largely self-educated immigrants; many years before, he had fled czarist Russia, she Lithuania. Early on, they knew their son was something special, as he outshone fellow students at the progressive Oak Lane Country Day School.

At an implausibly young age, Chomsky was sorting through the tumult of the time -- communism and fascism, the Bolsheviks, and Trotsky. He wrote his first school newspaper editorial, on the Spanish Civil War, at age 10; he claims to have rejected Marxism and settled on being an anarchist -- one who believes the human condition thrives best when there is virtually no government -- at age 12.

But it was in New York in the early '40s, as a precocious high school student, that his odyssey truly began. Those were days when the left was vibrant, when revolutionary talk pulsed through the streets and cafes and bookstores of Manhattan. Most nights, Chomsky hung around his uncle's newsstand in New York City, where emigres and dissidents talked over the Soviet Union's experiment with socialism and whispered their fears of Europe's surrender to fascism. It was there that he charted his own course and cultivated his unswerving dedication to the underdog.

Significantly, however, Chomsky never joined any group. The closest he came was promoting the idea of a socialist Palestinian-Jewish alliance before the creation of the state of Israel, which he has always opposed.

Later, as a student at the University of Pennsylvania, Chomsky, by his own account, was a distracted and not very dedicated student. Despite the influence of his father's noted work in Hebrew grammar, he claims to have fallen into linguistics as he searched for something interesting to do. But he took to it. After his first job, as an instructor at the University of Pennsylvania, in Philadelphia, he was invited in 1951 to be a fellow at Harvard. He and his wife, Carol Schatz Chomsky, who had grown up in the same Philadelphia neighborhood and whom he married in 1949, moved to Cambridge. He was passed over for a teaching position at Harvard - the legend is that university leaders were wary of the radical politics of the Chomsky family - and landed instead at the Massachusetts Institute of Technology in 1955. It turned out to be a perfect environment for Chomsky: The engineering-dominated school had little in the way of humanities and social sciences, so he and a few others were free to build a linguistics department more or less from scratch.

Chomsky settled in among the eclectic group of scholars in Building 20 and started the work that would change the way we think about how we learn and who we are. The Chomskyan revolution confronted the dominant school of thought in the social sciences of the 1950s: behaviorism. B. F. Skinner and the other behaviorists argued that all human action, including thought itself, is a simple series of responses to outside stimuli. By rewarding some behaviors and punishing others, behaviorists said, the world shapes everything we do.

The wedge Chomsky used to rebut behaviorism was linguistics - the detailed study of that quintessentially human behavior, language. Dismissing the behaviorist argument that young children utter words because they're rewarded for doing so, he instead suggested that all humans are born with an innate, universal capacity for language.

While the accident of birth has us speaking English instead of Japanese, German instead of French, in Chomsky's scheme, it is because of an underlying "deep structure," a kind of universal grammar, that we are able to speak any language at all.

Chomsky backed his theory with extensive technical evidence, but at its core was an elegantly simple idea: We are shaped by the world, to be sure, but we start out with innate gifts. And his critique of behaviorism and of the structuralist school of linguistics -- the idea that language, like all behavior, was developed entirely by training and by the external environment -- had implications far beyond the narrow, scholarly study of linguistics. It helped trigger what has since become known as the cognitive revolution: a whole new way of exploring how the mind works.

"It was like a bomb," says Steven Pinker, a professor of brain and cognitive science at MIT, a colleague of Chomsky's, and the author of The Language Instinct: How the Mind Creates Language. Some said Chomsky's new perspective had the same paradigm-shifting weight as Einstein's theory of relativity.

"Chomsky set the field on quite a different course, and most people wouldn't have gone into the field had it not been for him," says Brandeis University linguist Ray Jackendoff, a former student of Chomsky's. "I can think of one other person who has dominated one field, and that's Freud."

In the years that followed, Chomsky -- and a growing legion of students and followers -- worked on settling questions of how language "grew" in the mind from the original innate faculty he had identified. By 1980, Chomsky was promoting the "principles and parameters" model: the idea that the underlying language faculty consists of fixed principles combined with an array of parameters, or variables, that are each set to one of only a few possible values. "Language acquisition is the process of fixing the values of the parameters, kind of like answering a questionnaire," Chomsky explains. "A rational Martian scientist looking at us as we look at ants would probably say there is only one language, with peripheral variations." By the time the principles-and-parameters approach caught hold, of course, Chomsky was well advanced in his other life: political commentary. The catalyst, in the late '60s, was the Vietnam War, which he viewed as a crime against humanity and typical of the evil that the United States routinely practiced. Chomsky saw America's influence abroad as brazen economic imperialism, cloaked in the hollow promotion of democracy. He delved into covert wars and American intelligence activity in the Third World and developed such causes as his campaign against the oppression of East Timor.

At the same time, Chomsky crafted a withering critique of the intellectual culture, the media, and the academic world in which he worked. The basic theory, first laid out in such books as American Power and the New Mandarins (1969), was that intellectuals and journalists were participating in a process of whitewashing and indoctrination and were hopelessly subservient to established power. It was the special responsibility of intellectuals, he argued, to remain independent and expose lies. The vast majority of Chomsky's colleagues in academia do nothing of the kind, in his view, preferring to busy themselves within the carefully defined boundaries of acceptable debate.

"Intellectual life is mostly a racket," Chomsky says today.

"That's not so much true of the sciences, which is why I like it at MIT: Nature keeps you honest. But a good deal of intellectual life is corrupt and profoundly dishonest and almost has to be. The academic world is made up of parasitic institutions that survive on outside corporate support, so if people get out of line, there's going to be trouble. There's just no reason why those with power should allow entry to critical voices."

What passes for dissent is almost laughable, Chomsky believes: "So you get The New York Times being described, without irony, as the voice of the liberal left, just because they are occasionally slightly critical."

The media are a favorite target, in part because Chomsky sees them as part of a larger propaganda machine that chugs away in American life. "It's gone on for 50 years," he says. "After the Second World War, public attitudes were still pretty much the way they were in Europe -- social democratic. That scared the daylights out of the business community. So they began huge propaganda campaigns. Business was paying a third of the cost of school textbooks; they took over sports and recreation. And they funded films like On the Waterfront, portraying honest working men standing up against corrupt union bosses.

"Still, you look at public attitudes, and they remain roughly social democratic: People worry about the poor, they hope for better education, they worry about the environment," he says. "But the propaganda takes its toll. You just keep ramming it in people's heads: You're afraid of welfare mothers, crime, drugs, an unbalanced budget. Sooner or later, they're going to believe it."

It is the gospel according to Chomsky, and it is what has made him an icon to thousands of students as well as to so many of his intellectual peers. For the skeptical and the disillusioned, Chomsky became a cult figure over the years. He packed lecture halls from Cambridge to Paris. In intellectual circles, quoting Chomsky was always sure to prompt a knowing smile. It's just that, lately, it's been getting harder to tell if those were smirks all the while. It was not surprising that Chomsky's radical critique met with indignant resistance. For every convert, it seemed, there was at least one nonbeliever who saw him as a lunatic leftist, a brewer of conspiracy theories, an annoyance, a one-note tune. A few factors seemed to contribute to his fate.

First, there is the matter of how Chomsky was heard: the media outlets, the journals, the broadcasting venues that gave his voice a wide audience. The New York Review of Books was one soapbox for Chomsky -- but only until 1972 or so. Chomsky says that's because the magazine's editorial policy abruptly shifted to the right around then. But he couldn't seem to find a home with other publications, either. He went from huddling with newspaper editors and bouncing ideas off them to being virtually banned. The New Republic wouldn't have him, in part because of his unrelenting criticism of Israel. The Nation? Occasionally. But for the most part, mainstream outlets shunned him. Today, his articles on social and political developments are confined to lesser-known journals such as the magazine Z. Part of the explanation is that the nation's political mood has genuinely shifted. In an era when the left is so firmly out of fashion, Chomsky is the ultimate dinosaur. And although Chomsky was never a liberal, in the sense of believing that government could solve most problems -- indeed, his anarchism argues just the opposite -- he was lumped with the idealists that House Speaker Newt Gingrich regularly refers to as the counterculture. And as Gingrich, Ronald Reagan, George Bush, and -- most recently -- Bob Dole know well, there is much political mileage to be gained by bashing East Coast, liberal-establishment eggheads who "blame America first."

But it was not only the right that shut Chomsky out. In the intellectual circles of Cambridge and beyond, many of the left-leaning thinkers who would seem to be his natural allies also turned away. A chief complaint seemed to be his tireless promotion of an omni-applicable analysis. "It's an old Marxist style of analysis: a polemic. Everything all hangs together. No matter what happens, it benefits the ruling class," says Harvard professor Nathan Glazer, a liberal social scientist who has known Chomsky since youth. That kind of analysis, Glazer says, "can be tiresome."

Even friends acknowledge that Chomsky's personality has played a big role in his alienation. "He implies that people who disagree with him are stupid and ignorant. He is a brilliant debater and an out-and-out bully," says Pinker, Chomsky's colleague at MIT. "It's great fun if you're on his side, but not if you're suddenly the target. People storm off and hate his guts for the rest of their lives."

The hard feelings have come back to haunt Chomsky time and again. Allies were scarce, in just one recent example, when Chomsky defended the right of Holocaust denier Robert Faurisson to fight censorship by the French government. Even in linguistics, resentment festers. Chomsky has alienated legions; the field is littered with loyal-then-belittled disciples who broke camp. "He revolutionized linguistics but did it in a divisive way," says former student Joan Bresnan, now a respected linguist at Stanford University, in California. "He's a polarizer. He's created warring schools."

The ill will persists even as Chomsky refines his latest linguistics theory, summarized in his new book, The Minimalist Program. In the principles-and-parameters analysis, Chomsky's new approach focuses on the "principles" -- essentially, the bare bones of language formation, which, Chomsky suggests, is a surprisingly simple, elegant system, prompting fresh questions about the design and origins of the language faculty. Some scholars are hailing minimalism as the latest earth-moving revolution out of Building 20. "He's come out with major things every 15 years or so, and this will be a very major thing. It will be enormously important," says Chomsky's longtime MIT colleague Morris Halle.

But others are not so sure. "He's made radical changes in his program, but it's still based on this transformational architecture he developed in 1957," says Bresnan, who compares Chomsky's minimalism program to Microsoft's much hyped Windows 95 software. "Just as with Bill Gates, the programming cognoscenti know there are some cosmetic improvements, but it still has DOS at its heart."

The question, some colleagues say, is whether Chomsky is willing to entertain theories that go far beyond his own original ideas. Indeed, if there were the intellectual equivalent of an antitrust suit, it might have been filed against Chomsky long ago. "He does tend to stomp on arguments," says a colleague at MIT who asked that his name not be used. "He's not a grand old man, in terms of sitting back and letting 100 flowers bloom or letting the young people carry the torch."

As with his political commentary, some intellectual peers are starting to view Chomsky as a cranky naysayer who refuses to engage in some scholarly debates, because he says their premise is misconceived. His contrariness has doomed him to miss out on some of the most exciting things happening in academe today, they say. But for all those who argue that Chomsky has fallen behind the times both politically and academically, there are even more who argue that, at least in linguistics, it's simply not true. "People are very eager to ask, 'Has he lost it?' They're in a big hurry to write him off," says Jackendoff. "But it's more complicated than that."

Chomsky's theories are still on the cutting edge and in many ways still define the field of linguistics, and Chomsky plays a big role in synthesizing the work of others, says MIT colleague David Pesetsky. But because he is the dominant figure in the field, Pesetsky says, attacking Chomsky is the only way for some scholars to get attention for their theories. "The most striking fact is how consistently people with anything at all to say about language feel the need to strike some attitude for or against Chomsky's ideas," Pesetsky says. "It's a big problem."

Others welcome Chomsky's skepticism in the burgeoning debate about how the mind works. His demand for clear results wins him points with most scientists. In today's academic world, Chomsky says, it's all too easy just to "tell stories." He is the first to admit awe at how much we don't know. "Beyond very simple systems," he says, "no one understands much about how physical laws work. Try to figure out, for that matter, how the laws of hydrodynamics account for the flow of water in your bathtub or the swirling of cream in a coffee cup.... In the case of something as complex as the language faculty, we're far from serious understanding."

But if Chomsky's place in the scholarly realm is assured, his status as political commentator remains a far more tricky question. The most telling clue may lie in the extent to which he is isolated from the broad intellectual conversation on American life.

Chomsky himself bristles at the notion: "It's hard to feel 'marginalized' when I have to spend an hour a day just writing letters saying, sorry, I wish I could do it but have no time. Or when my schedule has to be arranged several years ahead and is so dense that phone interviews, sometimes even telephone calls, have to be scheduled, often months ahead. I know my wife and grandchildren would be delighted if only I were 'marginalized' a little; so would I, often."

It is only in a few places around the most "doctrinaire centers" -- National Public Radio, The New York Times, The Washington Post -- where he says he can't get in, whether it's a quote or an essay, commentary or an interview. (Though it was the Times in the late 1970s that called Chomsky the "most important intellectual alive.")

"The term 'marginalization' carries an interesting connotation," says Chomsky, "rather like 'exclusion.' One should have some care about this. When I was a student at Harvard, there were clubs I couldn't get into -- being Jewish -- but I wasn't 'excluded' from them, because I wouldn't have agreed to have anything to do with them. Similarly, I'm not marginalized by the many rather mainstream outlets and associations that I have no interest in being part of. Often, it's mutual."

Some in the media have said that Chomsky could get wider distribution if he stated his ideas more succinctly, in something approximating sound bites. But others in academia say that complex perspectives and radical conclusions simply don't have a place in today's marketplace of ideas, no matter how cogently put. "American political scientists ignore anybody who doesn't agree with them. They simply hate criticism, any criticism," says Thomas Ferguson, a political scientist at the University of Massachusetts at Boston. "It's more like a religion than social science." Similarly, he says, "international relations is virtually a closed field."

Ferguson -- and here Chomsky is in full agreement -- suggests that many academics in these fields hope to get policy-making jobs in the US government, so they eschew anything but mainstream ideas. But political scientist Joshua Cohen, a colleague and admirer of Chomsky's at MIT, says that Chomsky's exclusion shows how all American intellectuals have difficulty participating in the flow of civic life. "To the extent there is some kind of division between Chomsky and public dicussion - it's not the American convention," Cohen says. "There isn't the same connection between intellectuals and public and political debate as there is in France or Germany. You can't point to a lot of distinguished intellectuals who play a large role in public debate. It's just not what we do."

There are other ways of influencing the American political conversation, of course. Chomsky will be heard at lectures; he will teach; he will influence other op-ed essayists, even if he writes few such columns himself. "There are many chains of influence," says Cohen. "You would probably find Chomsky is an important link in many of those chains." So Noam Chomsky still reports to Room 219 in Building 20, still leads graduate seminars and undergraduate classes, and still writes dozens of letters a day. He comes out with stacks of them -- several inches of personal, typed letters -- and drops them on the desk of Bev Stohl, his trusted assistant.

How he keeps going at this clip is a source of wonderment, even among his detractors. "He does have characteristics that are not so much alienating but wearying," says Glazer. "It's his indefatigability. He always writes the last letter. You just have to give up; he's more energetic than any of us."

Chomsky's idea of a vacation, a friend says, is to work eight hours on correspondence, reviews, and other writings, instead of his usual 10 or 12. And he shows no sign of slowing down. He talks about good health, but it's usually part of a confession that he's not doing much about it. He says he knows he could be more physically active. His concession to the negative effects of caffeine is to drink a mixture of half-coffee, half-water.

This summer, he spent time with his family -- his wife, Carol; their three children, Avi, Diane, and Harry; and three grandchildren -- at a Cape Cod retreat he won't reveal much about, like most of his personal life. "I'm a very private person," he says. But friends hoped he was spending more time there than in past summers. "He's not 26 anymore," says Halle.

As Chomsky grows older, the question of his legacy is certain to grow in importance. What seems clear is that a range of future discoveries about the brain and language will be built on the foundations he has laid. His political radicalism, by contrast, is a building block that does not fit neatly anywhere just yet.

He may yet be remembered as a 20th-century Rousseau, a thinker disdained by his peers but later reappraised as a hugely influential philosopher. The clubby timidity of the American intellectual and political culture is partly to blame for his alienation. In the end, however, it is Chomsky's own zeal to remain an outsider that keeps him out of the game.

To Chomsky, staying in that position is a matter of integrity. It's what makes him what he is. "If I were lauded by the mainstream," he says, "I'd be doing something wrong." But those who think Chomsky deserves wider circulation harbor hope that this standoff with the mainstream might someday end.