I USED TO DRIFT through life confident that the cul-

tural flotsam and jetsam surging around me -- home computers, Mx missiles, video games, 12-year-old faces on fashion magazine covers--wouldn't affect my children, wouldn't prevent them from growing up in my admirable image. Well, my smug assumptions have just been squashed by Neil Postman's new book, The Disappearance of Childhood. Postman, a professor of media ecology in the communications department at New York University, has written a fascinating, lively, and disquieting treatise which concludes that the energy and idealism that characterize childhood may shortly be no more, as "the charm, malleability, innocence and curiosity of children are degraded and then transmogrified into the lesser features of pseudo-adulthood."

To understand exactly what Postman means, one need only reflect momentarily on the adults and children who confront us nightly on television "family fare." Savvy, manipulative, sharp-talking youngsters (of whom there is no better example than Gary Coleman of Different Strokes) are pitted against loutish, dim-bulb adults (the Archie Bunker archetypes) who, episode ofter episode, have to be brought into line and educated by their clever offspring. You'd have to search long and hard to find the idealized -- but not entirely unattainable -- view of childhood on which we were raised: the protective parent who instructs his or her children in the ways of the world, letting them grow up gradually and securely, making mistakes to be sure, but rarely straying too far from the comforting safety-zone of home. In this old-fashioned model -- which extended in an unbroken line fron Little Women to Father Knows Best--adults and children were demonstrably different: adults had a certain social status as card-carrying grown-ups, and the children's task was to develop the wisdom and experience that would someday allow them to take care of themselves and to nurture others.

This notion of the division between adults and children seems almost quaint today, a sign, Postman says, that the very nature and definition of childhood is changing. Childhood, he says, is a social artifact, a post-medieval product of mass literacy. Before universal adult literacy was achieved, he writes, there was little that adults knew or did that could be kept apart from children's concerns. So, until fairly recently, children were dressed like adults, treated like small, imperfect adults, and were even perceived as looking like little grown-ups. So profound were earlier cultures' lack of interest in childhood per se, that the ancient Greeks, for instance, had no word for "child" as we mean it; until the 1600s, the French, German, and English words for child expressed a blood relationship, not age. Only in the past 400 years, in fact, have we begun to appreciate what we now take for granted -- the delightful nature of children's prattle and games, the charm of their curiosity and innocence.

Postman posits that the idea of childhood -- and the concomitant growth of the modern family structure -- is a result of what literacy made possible; a secret, discrete adult society. "In a nonliterate world, there is no need to distinguish sharply between the child and the adult, for there are few secrets, and the culture does not need to provide training in how to understand itself." With reading, though, exclusively adult rituals could emerge: sexual matters became taboo for the young, and for the first time it was considered shameful for adults to demonstrate anything less than rigorous self-control in the presence of children. Elaborate codes of manners evolved, and children suddenly had much to learn before they could be accepted into adult society. In short, adulthood had to be earned.

In childhood's heyday (the century, Postman says, between 1850 and 1950), children had their own society, furniture, books, and clothing and "in a hundred laws children were classified as qualitatively different from adults, in a hundred customs assigned a preferred status and offered protection from the vagaries of adult life."

No longer. Today, with television the major purveyor of information about the world, with our images of men and women gleaned less from the pages of books than from TV's childish adults and preternaturally mature children, the line between children and adults has blurred. And, as children and adults increasingly share the same games and styles of dress; as parents proudly urge children to earn their own keep and to be their pals, not their charges, the notion that children should be exposed gradually to the world is disappearing.

With the emergence of insatiable media gobbling up and spewing out action-packed material 24 hours a day, not only are children bombarded with images of humanitiy at its most depraved, but these images are presented in a medium designed to appeal to the emotions, not to the intellect. As Postman writes, "It cannot be said often enough, unlike sentences, a picture is irrefutable. It does not put forward a proposition, it implies no opposite or negative of itself; there are no rules of evidence or logic to which it must conform."

The carnage and mayhem presented without comment or response on the evening news are as accessible to a 4-year-old as they are to his parents, but only the child is actually being introduced to the world with such sensational snippets. "Through the miracle of symbols and electricity our own children know everything anyone else knows -- the good with the bad. Nothing is mysterious, nothing awesome, nothing is held back from public view. . . . In having access to the previously hidden fruit of adult information, they are expelled from the garden of childhood."

Clearly, The Disappearance of Childhood is meant to be provocative, to be outrageous. Because he hopes to shock his readers, Postman writes as though no parent (or child, for that matter) has ever criticized a television program or even strode purposefully across a living room, muttering "What trash!" and turned off the set.

Postman also romanticizes childhoods of the past. Even during the middle and late 19th century -- probably childhood's finest hour -- the youth whose decline he now sees was only the happy lot of a select, protected few. After all, parental secrets can best be kept from children when parents are not their constant caretakers. It's easier to be regarded with awe and reverence by the young when there are others to help accomplish the exhausting tedia of childrearing -- darning socks, changing diapers, wiping jelly off small faces, blowing small noses. And this distance requires the existence of a servant class, whose own offspring are, obviously, not going to enjoy the same insulated childhood that they are paid to provide for others. The innocence of childhood has always been an exclusive property, to be zealously but inequitably guarded by several layers of society.

Even so, today, the threat is more profound. There's a gaping hole in even the most privileged child's defenses: the ubiquitous television set. Although Postman explicitly declines to suggest ways of reversing the anti- child trend, it doesn't take much imagination to infer what must be done. Parents, and teachers, and others whose job it is to protect children can intervene to mitigate television's worst effects. They can encourage their children to read (and they can read themselves). They can make a point of watching television with their children, commenting on and correcting its inaccuracies and exaggerations when they occur. Most important, by articulating and demonstrating the values by which they try to live, they can prevent TV's mean world from tainting children's lives. If we fail as our children's guardians, we will have sat by, acquiescing in the death of our sons' and daughters' curiosity, idealism and optimism. And with them will die much of our hope for the world.