According to Bill Moyers, his new series - A Walk Through the 20th Century With Bill Moyers (CBS Cable, for 20 weeks, repeated various times on Wednesdays and other days; check local listings) - is ''an invitation to think.''
Ubiquitous is the word for Moyers these days. Besides the new CBS Cable series, his widely noted, two- or three-times-a-week commentary on the CBS Evening News is probably the main reason that CBS News is now running far ahead of the two other networks; his ''Creativity'' series on PBS is scheduled to start rerunning in March; his ''Six Great Ideas With Mortimer Adler'' will start airing on PBS in October; and he is working on a CBS Report on the Rev. Billy Graham, to air around Christmas. All are invitations to think.
''It would be unsatisfying if those two-minute commentaries were all I was doing,'' Mr. Moyers says. ''That is too meager a diet for a newsman used to smorgasbord. The other projects make it a full meal.
''You can make a point in two minutes, but it is difficult to develop a case even though CBS gives me time just about whenever I feel I have something to say. But maybe I am not appreciative enough of those two minutes. Saul Bellow once told me that in this society, in order to be heard you must speak in short bursts of truth.''
Despite the enormous amount of work in which Moyers is involved, he seems more serene than ever as we chat in his office deep in the heart of the CBS News headquarters on West 57th Street. ''A Walk Through the 20th Century,'' he explains, utilizes film clips from many sources, all in the archives of the Corporation for Entertainment & Learning, the producer of the series.
''We try to let the material shape what we do. Ideas suggest themselves as we get lost in the alchemy of creativity. For instance, I do lots of interviews which are interspersed among the newsreels. The premiere is a comparison of Hitler and Roosevelt, their lives and their deeds. Later we will be doing the history of a small town, Marshall, Texas, where I was reared. And when we get to the second American revolution, the story of the civil rights movement, Ruby Dee and Ossie Davis are doing dramatic vignettes based on actual events in black history for which we have no film. Of course, in all cases we will also use archival film.''
The series is not done in strict chronology, and it begins with the Roosevelt-Hitler comparison. Why?
''When I was working on that episode I realized that in it was the most important message of the series. The irreducible truth of the 20th century is that when democracy stood against tyrrany and won, the confrontation could have gone either way. Suddenly I realized I had this powerful weapon in my hands which would allow me to say, 'Look! Take it seriously. . . . What if the Nazis had won?'
''People today find it hard to consider that there could easily have been another conclusion to World War II. History could have gone the wrong way. The totalitarian mentality could have prevailed. Although we are fraught with problems in this country, we still stand for liberty.''
Moyers makes it clear that he wants to make the past a relevant part of the present. ''I'm hoping to stimulate people to think . . . we are all figures in a great big family album. History should not be the abstract study it is made to seem now in schools.
''If I were not doing 'Walk' I would be out of my cotton-pickin' mind. Picking up pieces of flotsam and jetsam here and there is insufficient to understand what is happening in the world. This project explains that there is a very big backdrop on the world stage and you must learn to see everything that happens in the perspective of the backdrop we call history.''
Moyers likes to quote a critic who once called him an ''unregenerate if unfulfilled anthropologist-sociologist. ''In a sense,'' he says, ''journalism falls between those disciplines. I use the skills of those disciplines as a journalist to convey information. I believe this series is in the best traditions of television . . . to educate and entertain.''
About half of the 20-part series is completed, and plans are still in the works for the remaining 10. Moyers indicates that he hopes to interview Richard L. Strout, of The Christian Science Monitor, in one of the segments.
How does he plan to end the series?
''The last segment will be called 'Reaching Up.' It will look at how the journey from Kitty Hawk to space symbolizes the insatiable curiosity and quest of the human race in the 20th century. It all happened in this century alone.''
How does Moyers manage to do so much?
He shrugs. ''The secret is in keeping control of your ideas so you only do those things which really fascinate you. And you must collect around you good creative collaborators whom you trust and who know what it is you are trying to do. I have a first-class staff. And I chose as a collaborator on the scripts Bernard A. Weisberger, an editor of American Heritage magazine and a history professor.''
This critic has sampled several hours of ''A Walk'' and it appears to be a landmark series, destined to be considered a masterwork of the new cable era, if it continues on the course of the segments I have seen. And given Moyers's record, it is very unlikely that the quality will suffer. In one fell swoop, ''A Walk'' has catapulted CBS Cable and Mert Koplin's Corporation for Entertainment & Learning into the front ranks of TV documentarians.