Thelma Zeno Lavine is laughing again.

The other day it was Kant who set her off. On an earlier occasion it was Hume. This time, during a discussion of "The Sorrows of Young Werther," a saga of doomed love and self-destruction, it's Goethe and "the feeling of the void within."

"The sense of nothingness, the absurdity of human life," she explicates with the barest smile to a roomful of college kids. "The disintegration of 'enlightenment' thought . . . The 'romantic' notion of suicide.

"And I cannot help but add," she tells her students, "that the void is especially great when all the hamburger stands are closed."

The classroom explodes in what might be called reflective mirth.

"To function as a philosopher," allows George Washington University's Elton Professor of Philosophy, "is a profoundly comic experience."

What is the nature of reality?

What can be known? How can we know it?

Thelma Lavine grapples with such questions while other people -- to update Camus' epitaph for modern man, "he read the newspapers and fornicated" -- watch television and jog. She has reached no definitive conclusions, of course. Neither did Parmenides of Elea, who argued 2,500 years ago that the essence of reality is permanence, nor Heraclitus of Ephesus, who argued with equal conviction that reality is grounded in change -- nor, as yet, has any philosopher.

"Philosophy is comic because a lot of it is gamesmanship, and the efforts on either side of an issue are never entirely conclusive," says Lavine. "One of the things that intrigues my students is that I laugh a lot. The other day in class, someone said something funny -- I cannot remember what it was -- and I was laughing for at least two whole minutes. The whole class was breaking up. I was really embarrassed."

She sounds, with her well-starched Boston accent, like a rigorously trained academician. She looks, with her extravagantly black hair and cherried lips, like a Gypsy fortune teller. She brings both traits to her strange occupation -- that of contemplating and speculating in a town that celebrates action.

"There's no sense of a philosophic presence in Washington," she laments over lunch in her brick neo-colonial in Georgetown. "It's probably not a good city for philosophy . . . I wouldn't think that there will ever be a secretary of philosophy."

She nibbles at her chicken salad. "The philosopher can be useful, however. Because if he's trained at all, he can think. He can make distinctions, he can see inconsistencies. He can see a single line of thought developing, he can see the nature of dialogue and the opposing positions and the possibilities. Any graduate student, in principle, could take any political theory and shoot it full of holes."

Such people as Lavine, as someone once said about the very rich, are different from you and me. She does not read in bed, for instance. She reads sitting up, at her desk.

"The serious intellectual," Lavine says, "tends to be self-contained and self-involved. You can't be living the everyday life in which you do the 9-to-5 thing and then go home and do what everybody else does by way of amusement, recreation and all that kind of stuff. If you're an intellectual, there's no such separation. Whatever you do, you're always looking at it and thinking about it in terms of the perseverating ideas that concern you."

She studied at Harvard in the 1930s under such exponents of American naturalism as Ralph Barton Perry and C.I. Lewis, earning her doctorate in both philosophy and psychology. She remains an aficionado of psychoanalysis, pondering Freud in her spare time as a psychotherapy trainee at the Washington School of Psychiatry. And in the 30 years since she came to town with her husband Gerald Sachs, a career Treasury Department official who died last summer, she has gained a reputation as both a thinker and a teacher. "Inspiring, inspired, scholarly, compassionate," says one of her former students, Lisa Seigel. "She made me see how philosophy reaches into every single minute crevice of life. She taught me how to think."

"Her brilliance is in her simplicity," says one of her current students, Aaron Flamm.

"She is," says Paul Weiss, Heffer Professor of Philosophy at Catholic University, "a remarkably well-balanced, judicious, articulate person."

"Thelma is a high roller," says John J. McDermott, Distinguished Professor of Philosophy at Texas A&M. "She's very smart, very tough and very learned. She has an exquisite mind -- and she's willing to do business."

Lavine, doing business, is an evangelist for philosophy.

"It's not that people should be thinking about philosophy, it's just that they can't help it," she says. "More and more people in this country are becoming sensitive to their own perplexities and confusions. By virtue of having gone through a university education, they are trained somehow to be reflective. We are no longer a bunch of dummies. This is no longer Mencken's 'boobocracy.' "

Her classes at GW are celebrations of the dialectic, that fertile Hegelian fusion of far-flung notions. Dialectically, she and her students explore the interrelationships of philosophy and history, sociology, literature (Philosophy in Literature, dissecting such works as "The Metamorphosis" and "The Magic Mountain," is a perennial sellout), and what all these connections and clashes tell us about society and institutions.

It's a rare session that doesn't leap from the arcane to the conspicuous. Thus a rather correct discussion in Lavine's Social Philosophy class recently -- of how to subject a political theory to logical, ideological and psychological analysis -- became a merry melee when a student suggested taking a close look at Sen. Edward Kennedy's recent trip to South Africa.

"All hell broke loose," Lavine says. "I was simply going to talk about John Locke, but this was the absolutely perfect example. The people in that class will never again be naive with regard to politics. They will never again be swept up into the political rhetoric of the moment."

She has begun to reach a wider audience of late with her Bantam paperback survey of western thought, "From Socrates to Sartre: The Philosophic Quest," which grew out of her television series of the same name, a viewer favorite on Maryland Public Television's "College of the Air." (The series is currently enjoying a reprise on Channel 22, Sunday mornings at 11.) What sets her apart is not only her range of expertise -- she seems to have specialized in everything -- but also her talent for grabbing hold of ideas and getting them out into the open with the urgency of a fire brigade.

"Can you imagine a world in which nobody any longer asked the philosophic questions?" she writes in "From Socrates to Sartre." "It would be a world in which nobody penetrated below the facts of everyday life to think about what is real, true, valuable, just and meaningful . . . we would have become hollow men going through meaningless motions and our speech would be empty chatter."

That vision, Lavine argues, may already describe the pervasive intellectual strain in American philosophy -- namely, the analytic movement that budded half a century ago in Vienna, bloomed in Britain and spread across the United States like creeping hemlock (entangling, among other departments, the University of Maryland's, from which Lavine extricated herself in 1965). The movement's inevitable goal: "the elimination of philosophy," she writes.

"The sense of excitement has gone out of the big bombshell that was dropped by analytic philosophy," she says. "I think that there is a need right now for a more substantive approach to philosophy -- or the whole show is bankrupt."

Not everyone shares these views, of course.

"I think that's an extremely eccentric opinion," says Marshall Cohen, dean of humanities at the University of Southern California and editor of the influential journal Philosophy and Public Affairs. "Analytic philosophy is far from dead. It is American philosophy. And it's the most resourceful area of American philosophy."

One analytic position, as staked out by such philosophers as Austrian Ludwig Wittgenstein, holds that the "philosophic questions" cannot be meaningfully posed. Discourses on the nature of reality (truth, justice, etc.) are apt to be muddles of error and imprecision. The function of contemporary philosophy, say many of Wittgenstein's disciples, is to clarify language and expose errors in thinking through detailed logic and linguistic analysis.

"I destroy rotten argument," says one of today's crop of analytic philosophers, GW professor Peter Caws, in a tone reminiscent of Clint Eastwood. "There's a lot of sloppy thought out there. A lot of philosophical mopping up to do."

"He may destroy rotten argument, but he's not putting up anything in its place, you understand," says Lavine with a grin. "The analysts have maintained, above all, the autonomy of philosophy -- it is the realm of pure thought, uncontaminated by psychological, social, economic or other factors. So they have developed a technique, the technique of language analysis, which is totally autonomous and makes them the equivalent of some kind of scientists.

"I am absolutely opposed to that. My entire approach to philosophy is to show that it is generated out of human life."

She adds, "The time is now ripening in America for an ascendancy to a higher level of consciousness -- a higher level of self-understanding, such as Hegel and Marx provided in Europe. There is a new intellectual development in process in this country -- the rise of an American philosophy."

This new philosophy, she believes, will build on such disparate traditions as the empiricism of Hume and phenomenology of Hegel, taking up where such thinkers as John Dewey left off 50 years ago. It will break sharply, she asserts, with analytic philosophy. She is currently fleshing out her arguments in a book in progress, "American Philosophy and the Culture of Modernism," a study of developments in thought at the turn of the century.

"This is intellectual warfare," she says. "Intellectual battles are very real battles -- a fight to the finish. In a way it's less civilized than an ordinary military operation. Because in military operations, there are rules. There are things you don't do. There are longstanding international agreements about what is a legitimate form of warfare. There are no such rules in intellectual war."

Zeno of Citium -- whence Thelma Lavine's middle name -- was the founder of Stoicism, the philosophy of fortitude and self-control.

"My father gave me that name," she says. "He had ideas." She laughs. "It was part of his very sober view of human life. He was not exactly an enlightened optimist."

He was a designer of women's clothing. Her mother was a member of Boston's Jewish intelligentsia. "I have a strong moral sensitivity, and I think I get that from my mother," she says. "It was my mother who was the model of strength and power and drive. My father was more of a dreamer, a poet. He was very distant, very introverted, but very gentle."

She grew up in the suburbs of Boston writing poetry, reading and thinking. To outsiders her life must have seemed a model of culture and privilege -- not the turmoil of emotions it frequently was. Her father was a convert to Christian Science who disdained medicine. Her mother pointed proudly to the many doctors among her relations. Her father was a melancholy man who watched his business go bust, dying unexpectedly when Lavine was a young woman. Her mother was an energetic, spirited sort who successfully invested in real estate.

"Apparently my mother was fascinated by my father because he seemed so elusive," Lavine says. "He couldn't make up his mind whether he wanted to be married or not, so she waited seven years for him to make up his mind. She was a very beautiful woman and I think she made a very big mistake."

Lavine says she considered following her uncles and cousins into medicine, or perhaps becoming a literary critic and pursuing poetry, but ultimately gravitated toward philosophy and psychology, thus indulging her zest for the life of the mind.

"Deep in the darkening well the image sank," began a poem Lavine wrote at Radcliffe. "You can see already, in that poem, the influence of Freud," she says today. "In a sense I was constructing a metaphor for the unconscious."

She never wrote another poem. Instead, under the tutelage of a Harvard instructor named Raphael Demos, an ebullient Turk who taught her how to smoke a pipe, she took up the likes of Plato -- who considered poets the most dangerous of liars. She would go on to write such tracts as "Naturalism and the Sociological Analysis of Knowledge."

"Philosophy destroys your literary talent," she says. "Because philosophy demands analysis, organization, clarity, exactness, logical arrangement. And the philosophical sensibility starts to take over and dominate the literary sensibility. It ruins the kind of spontaneous creativity that you need for literary creativity."

She taught at Wells College and Brooklyn College before settling in Washington, the city of power and pragmatism. In her three decades here she has managed to avoid active political associations -- "My sense of the ideologue is too overriding for that" -- but has worked as a research fellow at the neo-conservative American Enterprise Institute and regularly instructs visiting Latin American military officers as a lecturer for the Inter-American Defense College.

She sounds as tough on the Soviet Union as Ronald Reagan, but calls herself a liberal who, for example, considered the ferment of the 1960s "refreshing." She is faithful to the theology of western liberalism, concluding recently, in a scholarly tract on Dostoevsky, that it is "sacred to humanity . . . a type of icon that the West would do well to recognize and revere."

Perpetually pensive, she's willing to take on almost any subject:

* The intellectual elite: "In the United States, it's the Supreme Court that serves that function. They interpret the founding documents that tell us who we are and what we're doing, and what we should and should not do. But they're not really the intellectual elite. Their function is not to be speculative philosophers. Am I making myself clear?"

* Abortion: "I think that if one tries to handle it on rational grounds, it has to be handled theologically. And that means that one has to deal with the theological claim that a soul exists as soon as there is conception, as soon as there is 'the quickening.' But what do you do with that? What is the validity of such a statement? On the other hand, you have to recognize that people believe it."

* Nuclear weapons: "I think the arguments against them are very nice arguments on behalf of peace and the dangers of nuclear war. But the rationality within the so-called madness of nuclear weapons is the deterrence value. Not only the deterrence value to the enemy, but to the world at large -- which, seeing a strong United States keeping on top of the arms race, has confidence that the United States will persevere."

* Bernhard Hugo Goetz: "I have a gut reaction like anyone else. I was listening to the radio this morning and the announcer was talking about 'the vigilante who drew his gun on these four teen-agers.' You see the ideological ploy here? 'These four teen-agers, these nice little kids who asked for five dollars' -- right? Of course, they had screwdrivers with them to enforce their request. And I got all excited at the radio and I said, 'That bastard! He's totally obscuring the point!' Which is not dispassionate analysis by any means."

* Sports: "That's probably the one big area of American life than I'm not really connected with. If I thought it would be a rich territory for me to explore, I would try to latch onto it somehow."

These days Lavine is working on her book, coediting another and teaching two courses at GW. The most immediate issue in her professional life, however, is not philosophical but logistical. She has been deprived of her accustomed Philosophy in Literature lecture hall and given one equipped for chemistry experiments. But as she tries to get her old room back in what she calls "a huge power struggle," she has attempted not to lose sight of loftier concerns.

"There's a real dichotomy in academic life, but that's nothing new," she says. "David Hume, for example, was obviously brilliant in philosophy in his time. And he couldn't get into any university because, although he was being considered and they were perfectly well aware of him, he was so antireligious, so shamelessly atheistic, that the administrative powers that be were not going to let him in, that's all."

The modern world, she says, promises both devastation and rebirth. Standing behind a slate counter outfitted with gas jets and a sink, she tells her students, "We live in an apocalyptic age."

A young man lingers after class to ask Lavine whether there's such a thing as a personal apocalypse.

"That's a very good point," she says, turning the concept over. She considers. "Really very insightful. In a sense, life is a series of apocalypses."

"Yes," the student agrees. "A series of minor apocalypses."

Lavine says later, "What I'm trying to do as an intellectual is to look below the surface of these series of minor apocalypses, to ask, 'What is going on here?' 'In what direction are we moving?' I have to understand these things. So do you. To live in the world without understanding them -- well, that would be very painful to me."

And Thelma Zeno Lavine is laughing again.