Many people have never heard of her. Yet to a sizable crosscurrent of Americans, Marilyn Ferguson represents the cutting edge of the 1980s. The reason is her provocative 1979 book, ''The Aquarian Conspiracy,'' on the subject of ''personal and social transformation in the 1980s.'' (''Aquarian'' refers to this modern era as the age of Aquarius, a time of spiritual awakening; ''Conspiracy'' comes from Teilhard de Chardin's notion that the world needs a ''conspiracy of love.'')
The book has sold over 375,000 copies. It is still on display in stores, moving as briskly as it did four years ago, according to J. P. Tarcher, her publisher.
Ferguson's theme is somewhat akin to Alvin Toffler's in ''The Third Wave'' ( 1980): epochmaking changes in the world, with the United States as the ''matrix.'' But whereas Toffler's wave is made up of the external world of things and events, Ferguson's change is more internal, perceptual - taking place in thought.
John Naisbitt, author of the megapopular ''Megatrends'' (1982), has gone so far as to tell audiences that ''The Aquarian Conspiracy'' is ''the hard-core stuff'' of which his book is ''the soft core.''
Ferguson, who grew up in a small Colorado mountain town and now lives in Los Angeles, is a trim, soft-spoken woman who never stops working. She dictates letters at the beauty parlor. She travels frequently (''I feed on conferences''). During a visit to Boston recently, she told this reporter that the most common reaction she gets from readers is: '' 'Thank heavens you wrote that book! I thought I was crazy until I read it.' ''
Drawing on a 10-year study of thinking that took her from brain research and behavioral studies to spiritual esoterica, Ferguson suggests that the logic-centered thought of a scientific, postmodern world is beginning to be balanced out by a thinking that is more intuitive and subjective. People are starting to listen as much to their ''heart sense'' about what is right, she says, as to their intellect. And they are finding she says, their intuition outpaces their understanding.
The achievements of the 20th century, Ferguson states, (in physics, technology, further establishment of democratic and educational freedoms) have created an opening in thought for average individuals to grow and express themselves in ways not known before.
''You can break through old limits, past inertia and fear, to ... richness of choice, freedom, human closeness,'' she writes. ''You can be more productive, confident, comfortable with insecurity. Problems can be experienced as ... a chance for renewal, rather than stress.''
Ferguson suggests such change is taking place partly because today people are not waiting for their own feelings to be legitimized by an authority figure - such as a minister or a psychologist. She says people sense that the material world is not a final condition. As a result, they are asking basic questions for themselves that in the past have been the province of the philosopher or theologian, such as: What is the relationship between consciousness and the external world?
Reading Ferguson is like digging into a slice of intellectual cheesecake. Ideas from dozens of distinguished thinkers - from Mohandas Gandhi to the latest Nobel laureate - are apt to be crammed into practically the same sentence.
Many of Ferguson's perspectives have been influenced by ''split-brain'' research, which suggests that logical/rational processes are found in the left side of the brain and intuitive/emotional properties in the right.
Responses to the book are diverse, even among thinkers working closely with the theme of change. Some see it as the natural outcome of a society reaching new heights of affluence, some as a search for spiritual values. Some feel the book captures the last gasp of the '60s counterculture movement. Others say it represents only the beginning of a larger, more mature pattern of change. Many question whether as many people are involved as Ferguson suggests.
James Ogilvy, a research fellow at SRI International and co-author of ''Seven Tomorrows,'' a thoughtful book on future social scenarios, feels Ferguson's book documents what is more aptly described as a ''shift'' than the all-out ''revolution'' she depicts. He says the shift shows people moving away from ''the old order - status, material prosperity, hierarchy.''
One of Ferguson's most cogent critics is Michael Marion, editor of Future Survey. Marion says: ''Although a transformation in values, perceptions, and institutions is desirable, it is far from inevitable. Making a religion out of social change - developing a body of unquestioned belief derived from concern for the human condition and hope for a better world - only serves to deflect energies away from the hard work that must be done.'' Marion also feels the milieu Ferguson associates herself with is too often acritical and superioristic , if not childish.
Among the questions remaining for readers and critics to sort out:
* Are there any coherent principles underlying the changes Ferguson cites?
* Is ''personal transformation'' more than a new way of packaging the perennial religious idea of salvation? If so, how deep is its moral undergirding?
* How broad is Ferguson's historical perspective? Does it pick up the strains of ''crossbearing'' and martyrdom that have often accompanied change?
* Is her message of personal transformation capable of dealing with evil? It could be said that hate and lust, for example, also begin in the mind.
Ferguson answers criticism with the assertion that critics always know why something can't change before it actually does. She criticizes the media in general for ''fashionable cynicism.''
She feels that many of the ''transcendent'' values of the '60s have worked their way into practice in the 1980s as a result of individuals who, when faced with a difficult world, look inside themselves for answers. She insists the transformation is real and that it will continue.