HOLDING FAST to a semblance of pageantry, about 100 academically robed scholars paraded across the Mall last Sunday afternoon as part of the opening ceremonies of the Smithsonian's seventh international symposium. Kilted bagH pipers, skirling "The Conundrum," a 19th-century Scottish competition march, led the procession from the Smithsonian castle to an auditorium in the Museum of Natural History.

In the back of the group was Dr. Rene Dubos, the 80-year-old scientist-environmentalist-philosopher-optimist who was to deliver the opening lecture of the symposium.

Dubos, in firm health and with only a slight stoop, was following the others. But in many minds, he was actually leading them by the forwardness of his mind that has produced more than 30 books since 1940, by his sense of direction in which he believes that "the difficulties of our time ... are not reasons for discouragement," and by his willingness to walk alone when he thinks the times deserve better than louder speeches and madder music.

Among the assembled scholars, Dubos delivered a carefully reasoned lecture on technological and social adaptations to the future. He breathed feeling into theories.

That has always been the gift most appreciated by his followers, from his fellow scholars who have been giving him so many humanitarian awards and honorary degrees that the prize-giving is almost a cottage industry, to the readers of his books. One of them, the late anthropologist Loren Eiseley, called Dubos "a scientific spokesman of superlative rationality . . . and a justifiably admired scholar." His best known work, "So Human an Animal," appeared in 1968 and shared a Pulitzer in nonfiction with a Norman Mailer's "Armies of the Night." It was dedicated to "the skies of the Ile de France," the region of his homeland north of Paris where he was born in 1901, and to the skies of the Hudson River Valley, where he keeps a farm.

The book presented a favorite Dubos theme, the adaptability of humans. "The most frightening aspect of human life is that man can become adapted to almost anything, even to conditions that will inevitably destroy the very values that have given mankind his uniqueness." That appears to be a statement of pending gloom, that if our adapting to a world of nuclear bombs doesn't kill us then gulping too much saccharin will.

But the Dubos of that 1968 statement has developed into a different and subtler mind. Speaking last Sunday at the Smithsonian, Dubos said that man's adaptive nature may well turn out to be a survival skill. He spoke of "the creative aspects of adaptation." It is the process by which "modern societies are learning to anticipate some of the likely consequences of action they are contemplating, and of the natural and social conditions to which they are likely to be exposed in the future." What needs remembering, Dubos argued, is that "human beings are rarely passive witnesses of threatening situations. The logical future, determined by past and present conditions, is less and less important than the willed future which is largely brought about by deliberate choices -- made by the human free will. In my opinion, our societies have a good chance of remaining prosperous because they are learning to anticipate, long in advance, the shortages and danger they might experience in the future if they did not act preventively."

Presenting opinions is not what projected Dubos into the heights of scholarship. It means that at 80 he is unexpectedly becoming a figure of controversy, one who is dismissed by younger environmentalists who might otherwise be among his devotees and boosters. Dubos may be facing one of the problems of longevity. He was a hero to one generation, as when he was the celebrated microbiologist at Rockefeller University in New York who discovered the miracle drug gramicidin in 1939 and helped begin the antibiotic era. Who can estimate the number of lives saved because Dubos found a bacterium in a cranberry bog in New Jersey that assisted the natural defenses of the body to fight pneumonia germs.

But to the current generation that takes miracle drugs as unmiraculous, and looks for leaders to defeat illnesses caused by industrial abuse of chemicals and not microbial pests. Dubos gives the appearance of being a genius who keeps too many ideas in his head at once, a man who lets conflicting views wear out their welcome in his mind. Instead of easing into his ninth decade as a sage elder applauded universally, Dubos now hears jeers. Respectfully sounded, but jeers nevertheless.

His recent opinions have brought them on. In New York City, where he lives with his wife of 35 years, Jean, Dubos supported the construction of Westway, the proposed highway on the lower west side of Manhattan. He argued that the public waterfront parkland that would cover the proposed underground highway would be a greater benefit to citizens than if the funds went into the improving of public transportation. In "Celebrations of Life," his most recent book, he wrote: "I know that New York City subways and buses should be improved -- even if this does contribute still further to the core city by encouraging people to move out of it, but I am even more convinced that creating a park with easy access to the lower Hudson would be an immense contribution to the enjoyment of life in New York City for both inhabitants and visitors."

Rafe Pomerance, president of Friends of the Earth and an articulate leader of those opposed to Westway, believes that Dubos has a superficial grasp of the issue. "We have several million people using the New York transportation system every day, and they need the available resources the most. If Westway is built, the tragedy is that of the New York subway system, already in a state of deterioration Dubos' statement is not really sensitive to the desperate needs of the subway system. Just read the papers everyday. The transportation system is the key to the quality of life in New York."

In "The Amicus Journal," a publication of the Natural Resources Defense Council, Dubos said that "The pollution that really matters is personal habits. It isn't the air. Over 95 percent of environmental cancer is caused by personal habits, and there are two that account for the majority of the cancers: smoking and drinking. Cancer due to exposure to the sun is also increasing enormously. The truth is that you need massive amounts of exposure to most things to get cancer."

This opinion positioned Dubos well outside of activist environmentalism. "I don't know why he buys that line about personal habits," says Robert Alvarez of the Environmental Policy Center. "There is quite a bit of data and evidence concerning exposure to carcinogens -- in the workplace, in utero exposure to radiation -- that comes from human beings themselves. This is not data from animal tests. It's from human beings. It shows that a significant fraction of cancers and other diseases are caused by involuntary exposure to man-made carcinogens. There's also a moral issue: When you light a cigarette or go to the beach, you do make some voluntary decisions about your health. But if you live near a nuclear weapons plant and if you are exposed to an accidental radiation release and to a known carcinogen, that exposure is involuntary. Dubos is saying that free will is the basic way to reduce cancers, but that's not so."

Others argue with the Dubos outlook -- what he calls "optimism, despite it all." Lewis Regenstein, vice president of the Fund for Animals, believes that Dubos is much too much the bright-sider: "You can't be knowledgeable about what's taking place -- the destruction of the earth and its ability to support and sustain life -- and be especially optimistic about our future. Dubos' optimism is as misguided as it is eloquent. What he writes sounds so smooth that it sometimes lulls us into the fallacious view that everything is going to turn out all right."

Dubos, who retains a French accent, was born in February 1901 in a farming village in the Ile-de-France countryside 30 miles north of Paris. In Henonville, Dubos was the son of the community butcher and the grandson of a house painter. His mother worked as a seamstress, by financial necessity. Dubos' parents met in Sedan in the northeast of France when the butcher boy served in the army. He was in uniform during World War I when killed in 1918 by a battle wound to the head. By then, Dubos' intellect, spirit and what would be his lifelong concerns had been given raw shape by his mother. He tells of one evening in the family's living room when his mother, who had been forced to leave school at 12, opened "the only learned book in our home," the "Petit Dictionaire Larousse." In "Celebrations of Life," Dubos' most autobiographical book, he recalls this evening when he and mother turned to a chapter devoted to the "Grandes Ecoles." "This provided both of us with material for daydreaming as to what my future should be. I do not know whether she had a clear notion of what the Grandes Ecoles stood for but it is certain that my attempts at a life of scholarship have their origin in her attitude, not only on that particular evening, but throughout my teen-age years . . . Whenever I have been successful as a scholar or otherwise, there comes to mind the pink pages at the end of the Larousse dictionary where, for the first time, I read the brief descriptions of the Grandes Ecoles and thus obtained a somewhat concrete image of a world larger in scope and more sophisticated than the one in which I had lived."

Dubos looks back on his boyhood village life as an educational opportunity that he absorbed almost subconsciously. Children saw parents working with their hands at trades that produced goods -- meats, dresses -- needed for living. When old enough, the children moved from observers to participants. Dubos would recall in "Celebrations" that "the human atmosphere of the village or the small town still had, in my youth, the demographic, psychological and emotional dimensions of the tribal structures in which humankind lived until the agricultural revolution 10,000 years ago, and of the villages in which the immense majority of the human population has lived, on all continents, until our times. The most important problem of urban planning may well be to recreate, within our large cities, the equivalent of the diversified unit of a few hundred people in which the social evolution of humankind took place, and to which we are still adapted today."

Beyond the meadows of the Ile-de-France villages was Paris. Dubos went to high school there and two years later, in 1921, earned a degree at the Institute National Agronomique. With soil science appearing to combine his feelings for the land with his need for a profession, he went to Rome to work at the International Institute of Agriculture. He left in 1924, to travel by boat to the United States. On board, he met a bacteriologist of Rutgers University who suggested that school as a fitting place for Dubos to study for his PhD.

This shipboard friendship, a "quirk of fate," as Dubos has called it, changed the direction of life.

With a doctorate from Rutgers, Dubos took an assistantship at Rockefeller. Except for two years in the early 1940s it was to be an association of a lifetime. Dubos retired as a full professor in 1971 and is now professor emeritus of environmental biomedicine at the University.

Entering his ninth decade, Dubos has suffered "more than an average share of organic diseases" over the years. But as he walked with the scholars across the Mall last week, and at the lecture and reception following, he had the healthy granular complexion of a seasoned farmer. He is a genial extrovert, given easy to conversation, and has a cheerful smile that breaks out when he remembers funny stories.

One morning last week, when he took time out from the three-day Smithsonian program to relax, Dubos recalled that one of the turns in his professional life as a microbiologist came at 65 when he decided to leave the cloister of science. "Until then I was only a laboratory worker." Going into the world, he recalls being "overwhelmed" by the example of lone citizens who had learned "to think globally but act locally." He tells stories of "human interventions," from the Queens, Long Island, citizen who helped transform Jamaica Bay from a swampy garbage dump into a bird sanctuary, to Chinese peasants restoring their forests.

What about St. Benedict, Dubos was asked, the sixth-century monastic leader and one of the world's first environmentalists. He waved his hand grandly and announced, "By temperament, I am a Benedictine, not only by my sympathies, but by my convictions -- the conviction that human beings should manage the environment wisely."

In "A God Within," a 1972 collection of essays, Dubos included a chapter on "Franciscan Conservation Versus Benedictine Stewardship." He said that something more was needed than only reverential feelings toward nature, as St. Francis believed. It's necessary to imitate the "creativeness" of St. Benedict: "The first chapter of Genesis speaks of man's dominion over nature. The Benedictine rule in contrast seems inspired rather from the second chapter, in which the good Lord placed man in the Garden of Eden not as master but rather in a spirit of stewardship . . . The Benedictine practiced a democratic administrative system of home rule and tried to achieve a living relationship with the physical world around him."

Although a lay member of three Benedictine monasteries, Dubos, as is common among scientists, keeps a distance from religious dogma. He feels religion rather than thinks it. He recalls one Christmas a few years ago. While reading the New Testament he had a deep and sudden "sense of the real presence of Jesus." The precise teachings of the church "don't concern me very much. But on the other hand, the ritual of the Christian Church helps me to relate to the rest of the cosmos."

"I have enormous emotional appeal for Gregorian chant."

As a scientist on the periphery of formal religion but who has a yearning and need to be at its spiritual center, Dubos has a duality that carries over into his secular thinking. He is aware of the criticism directed at him. "I know that a large percentage of contemporary enlightened people feel that any form of optimism is practically incompatible with the realities of our times," he wrote a year ago. But last week, as though his emotions were filtering into a zone of new detachment he said that "it is no longer a difficulty in my life that I, in all sorts of situations, take ambiguous positions."

At 80, longevity seems to have produced an intellectual serenity in Dubos, a peacefulness of the mind by which a man lives in one world but thinks in many. Far-flung leaps from one to the other are bound to occur, skewering absolute consistency -- perhaps as when Dubos calls himself "a despairing optimist." He is at peace with himself because, from his writings and conversations, he is man who sees the world imperfectly but sees the imperfections clearly. graphics: (Photo