Barbara Tuchman. `I would call [this] an Age of Disruption ... a period when we've lost belief in certain kinds of moral understanding of good and bad.'

She's a Pulitzer Prize-winning student of kings and popes and presidents, a public figure in her own right. But most of Barbara Tuchman's real work -- the writing that brings history alive for thousands of readers -- happens in the privacy of her home. In her friendly manner she offers a visitor her ``husband's favorite chair.'' She seats herself at her cluttered desk next to a wall of color snapshots of grandchildren and 50-year-old family black-and-whites.

The only cleared space on her desk, however, is occupied by the manuscript of her latest book, dealing with the American Revolution. Scattered about are the periodicals that reveal her eclectic interests: Foreign Affairs, Daedalus, the Harvard Library Bulletin, Art & Antiques. Among the photos is one of then-President Carter, book in hand, at an outdoor table with Vice-President Mondale. ``To Barbara,'' it says in Mr. Mondale's scrawl, ``We begin every meeting by reading from Tuchman.''

Not surprisingly, Mrs. Tuchman's agenda for the 21st century seems to blend her public and personal interests. It includes such prominent topics as nuclear war and the environment. But it puts its leading emphasis on morality. Above all, it is an agenda firmly rooted in her understanding of history.

Tuchman begins the discussion with the issue of nuclear weaponry -- although that is not in the No. 1 spot on her agenda.

``I wouldn't put it at the top because -- although I haven't got much trust in humanity's common sense -- I just somehow don't see it all exploding,'' she says. ``I can't say why. I suppose it's only because it just seems too extreme to happen. All these articles that tell you we're on the brink of exploding, blowing up the world and so forth, I should take seriously -- but I don't, really. Maybe because I'm just unable to conceive of it.''

In her own way, however, she has tried to ``conceive of it'' in ``A Distant Mirror,'' her widely read book on 14th-century Europe.

``I was looking for a model or an example of what happened to society in a major lethal disaster,'' she says. The ``disaster'' was the Black Death, a plague whose recurrent cycles so ravaged Europe that one-third of the population died.

``That seemed to me the most extreme [disaster] that had happened in the course of history,'' she says. ``I chose that, the Black Death, as a model of what might happen from a nuclear explosion.''

``But what I found,'' she continues, ``was that the 14th century had so many disasters and violences that you couldn't isolate or determine exactly which trouble came from the plague. And, in fact, I came to the conclusion that the various troubles did not all necessarily come from the plague by any means.''

She chose the 14th century as a ``mirror'' for the 20th century, she says, ``because it was so distinctly an age where everything was [disappearing], everything that people believed in.''

If she were a 21st-century historian looking back at the present day, then, how would she characterize it?

``I would call it an Age of Disruption,'' she says.

We live, she explains, ``in an age where things seem to have gotten beyond control.'' The weapons race, for example, is subject to ``our relations with the Soviet Union'' -- which, like many elusive problems, ``keep on getting away from us.''

More important, in her view, is the disruption of man's relation with the environment. ``This loss or deterioration of the natural world,'' she says, ``is probably the No. 1 one problem -- because I think it's already more with us than is the nuclear.''

A great lover of nature -- as is evident from the well-cared-for acres of her southern Connecticut estate -- she is concerned about ``the loss of the products of the natural world that we live by: trees, water, the stripping of forests and damming of rivers, the poisoning of the air, the loss of forests in the tropical world.''

``All these things,'' she says, ``are raising real dangers.''

Yet even the environmental issue is superseded in significance by another. ``My own concern is something else,'' she says, something she describes as ``the real deterioration in public morality.''

With the writer's penchant for specifics, she points to current events. She has been deeply disturbed by revelations that National Aeronautics and Space Administration officials knew about problems with shuttle booster-rocket seals long before launching Challenger last January. The fact of their ``knowing that there was danger and going on with the program without rectifying the troubles,'' she says, is ``so shocking that you can't quite absorb it.''

``That's only one small example of a much larger decline in public morality,'' she adds, ``[which] seems to me to pervade many fields of current life.'' She also points to ``cheating on the stock market'' and, in the political realm, the ``sale of influence'' and the corruption of elected officials. Status and power PARTICULARLY damaging to public morality, she feels, is the current electoral process. ``I see as a dangerous development,'' she says, ``the emphasis on ... fund raising.'' Campaigns are no longer based on ``the beliefs or functions of the person,'' she says, but rather on ``what kind of artificial image [the candidate] can project through professional fund raisers, whose effectiveness is determined entirely by their skill in certain methods [rather than by] the quality of the person they're selling.''

``I think this is lowering the quality factor -- if we can say that, [since] it's never been very high -- of the people we're engaging in government,'' she says. ``And that's serious, because we depend for common sense and rational policy on the kinds of people we put in office.''

Where does the problem come from? It's the result, she says, of ``the grip of status and power.''

``Everybody who gets into government wants to exert power and hold onto it,'' she explains. ``When they see things happening which are clearly signs of failure, they don't ring a bell ... because they're afraid of losing their position. They don't want to tell the boss -- whether it's Chiang Kai-shek or Reagan or Nixon or whoever it is -- what he doesn't want to hear.''

``You know,'' she muses, ``I say to myself, `If we could change the rewards -- if, instead of status and power, people got their reward in life through some other satisfaction.' But I don't think that's possible, either, because what does move people to really energetic action is doing something for themselves.'' In the Middle Ages, she says, ``they used to call it greed.''

The problem of public morality, for Tuchman, is mirrored in private morality. The two, she says, ``go hand in hand,'' because when ``this sinking of public morality'' appears ``so normal'' to the citizenry, ``they naturally apply it to themselves'' and begin to behave the same way.

But hasn't that always been so? Drawing from her rich historical store, she casts her mind back over Restoration England, Hogarth's drawings of poverty and squalor, and the early years of the Industrial Revolution. ``I suppose there have always been times when people have acted immorally,'' she concedes. What is new is ``the extent of public immorality making itself so obvious to the average citizen.''

And that, for Tuchman, is the ultimate disruption. ``When I speak of disruption,'' she says, ``I mean a period when we've lost belief in certain kinds of moral understanding of good and bad. I think that has left many people feeling uneasy, because ... they don't know how to behave, they don't know what's right and what's wrong.'' Culprits and models ARE there obvious culprits? Tuchman points at popular journalism and television entertainment -- which, she says, are ``really pretty deadly on any level of taste or any level of ethics.'' She then extends the list to include contemporary fiction.

In the ``average novel of the present,'' she says, the ``source of tension or drama is always in some very aberrant situation -- you know, somebody's committing incest, or trying to murder his mother, or he's insane, or he's alcoholic, or whatever. ... There's no sense in the author of viewing it as -- well, I don't want to say an immoral situation, but in a way I do. He's got no sense of why he's telling it except for the degree of shock and excitement that he can introduce.''

One problem, she feels, is ``the absence of admirable models'' in history and literature, where too often ``the unadmirable'' characters are successful. She especially faults journalism for ``emphasizing the shock value of wrong and of disaster and morbidity.''

``I think journalism has to try and make good actions ... more newsworthy,'' she says. ``When you see some group which has cleaned up its local river and brought the salmon back, or a family that has brought up six sons on no kind of income, all of whom turn out to be effective citizens -- that sort of thing can be made more attractive to the public.''

If admirable models are missing, however, that may be because of the absence of what she calls ``religion as a major force in everyday life.''

``I don't know how much less people really relate to religion or churchgoing [these days],'' she concedes, ``because ... I've never been a religious person. But I do think that there's a kind of absence of common understanding, particularly with the young as they grow up, of what's good behavior and bad behavior, and what's right and what's wrong. That is disappearing.''

That ability to distinguish good from bad is something Tuchman obviously practices herself, even in the minutiae of her daily life. When she was buying presents for her infant grandchildren, she says, ``I always used to make an effort to get toys that were not these horrid, primary, plastic colors ... but only to buy toys that I thought were pretty or attractive -- so that the children wouldn't get used to ugly things.'' Women and society `YOU know,'' she adds, ``if the growing population is given nothing but the shoddy and the artificial and the false, they're going to have more and more difficulty in discerning the difference between good and bad.''

But this ``growing population'' of children, she fears, is not being taught how to ``get hold of their own lives.'' She admits that getting hold of life is not always easy -- especially for women. The issue of ``women's place in society'' is ``something that still has to be solved and worked through'' in the future. She says she has little faith in ``the solution of the new woman'' or in ``feminist'' approaches. ``Unless [women] have part-time work, which nobody's satisfied with, or a remarkably cooperative husband, something has to give.''

How has Tuchman managed to ``get hold'' of her own life?

``I never thought I was particularly smart,'' she says with a self-deprecating laugh. But ``over my years I've used myself. I think people don't do that enough. They let things happen to them. That's no way to learn.''

Is that sense of passivity related to the influence of television.

``I don't know whether television's responsible or whether it's responding,'' she says. She dismisses the excuse for poor programming given by television executives who say they are simply giving the audience what it wants. ``There's a missing quality of responsibility there,'' she asserts.

Asked whether, in an Age of Disruption, she can identify any single thing most needed in the next century, she replies without hesitation.

``Probably personal responsibility,'' she says, explaining that she means ``taking responsibility for your behavior and your expenditures and your actions, and not forever supposing that society must forgive you because it's not your fault.'' A prize-winning writer of history

``I'm not trying to teach anything: I never wanted to be a teacher,'' says Barbara W. Tuchman, who is probably America's best-known contemporary historian. ``I am a seeker of the small facts, not the big Explanation,'' she has written, ``a narrator, not a philosopher.''

Judging from the popularity of her work, thousands of readers feel she has succeeded. The books ``The Guns of August'' (1962) and ``Stilwell and the American Experience in China'' (1971) won Pulitzer Prizes. More recently, ``A Distant Mirror'' (1978) and ``The March of Folly'' (1984) have been highly praised. Her goal, she has written, is ``to write history so as to enthrall the reader and to make the subject as captivating and exciting to him as it is to me.''

Born Barbara Wertheim, daughter of an influential international banker and publisher in New York City, she graduated from Radcliffe College in 1933, beginning her writing career as an editorial assistant and writer with The Nation magazine in 1935. She later served as United States correspondent for the British journal New Statesman and Nation. Her first book, ``The Lost British Policy: Britain and Spain Since 1700,'' was published in London in 1938.

Widespread recognition came with ``The Zimmerman Telegram'' in 1958 and its condensed version in the Reader's Digest the following year. Her essays have since appeared in The New Republic, The Atlantic, Esquire, Foreign Affairs, The Christian Science Monitor, and other publications.

Mrs. Tuchman counts her early reading of fiction -- especially the tales of Sir Arthur Conan Doyle and the historical novels of Alexandre Dumas -- as a strong influence on her career. But she distinguishes sharply between history and fiction. ``I do not invent anything, even the weather,'' she told an audience at Radcliffe in 1963. ``Leaving things out because they do not fit is writing fiction, not history.''