How we maintain our privacy in the information age, how babies grow, and how different people cope with old age and dying are among the topics in these books on the various stages of life.

The danger used to be so much clearer and more focused: From George Orwell's 1984 to Costa-Gravas's "Z," the enemy was the state. For dissidents in late-1960s and early '70s America, it was the FBI's Cointelpro and the CIA's Operation Chaos.

Though Big Brother's malice was infinite, his tools were limited and cumbersome -- phone taps that needed to be physically put in place; agents who crept around stealing documents; a small army of spies to watch, follow and listen. Now, according to Charles Sykes in The End of Privacy (St. Martin's, $24.95), the web of surveillance in which we live has become almost seamless: Corporations collect data not only on our buying habits but also on our preferences and the way we think. Employers count phone calls and key strokes, read e-mail, hire spies to perform background checks and make staffers pee in cups. Insurance companies force doctors and therapists to report information once considered confidential and that could put credit status and employment at risk. On the Internet, says Sykes, some of the biggest commercial Web sites "have already entered agreements to pool information about their customers into a massive new system that now tracks the behavior of tens of millions of users." And all these organizations, corporate and governmental, share information freely with each other.

"One of the ironic consequences of the Cold War," Sykes writes, "has been the transfer of much of the surveillance know-how of the nation's intelligence agencies to private companies, including those in the business of tracking the likes and dislikes of consumers."

Periodically, a ripple of concern about privacy surfaces in Congress, only to vanish under pressure from the corporate world and the FBI. President Bill Clinton, along with Al Gore, has been a relentless enemy of privacy, attempting to ensure government access to all Internet dealings, and even to criminalize the encryption devices that protect such communication.

Sykes cogitates on the meaning of privacy across cultures, and what it does to human beings to be so relentlessly known and exposed. He discusses talk shows and our culture of therapy, President Clinton's affairs and Princess Diana's death.

The writing in The End of Privacy is intelligent and concise, but the tone seldom varies; the reader eventually begins to wilt under the relentless cascade of detail. Still, this book represents a hugely valuable service and a tremendous job of research. It should spur urgent public debate.

The most convincing myths are those in which profound personal belief weds apparent scientific proof. Among them are the truisms that cancer patients fare better if they remain cheerful and that prayer can speed physical healing. In The Myth of the First Three Years: A New Understanding of Early Brain Development and Lifelong Learning (Free Press, $25), John T. Bruer shows that our prevalent beliefs about a child's first three years are created by just such a fusion of collective wishful thinking and misunderstood science. A great deal of public policy is based on the idea that these years are crucial in terms of emotional and intellectual development -- not just because a neglected or unloved child will carry the repercussions with him forever, but because the very structure of the brain demands certain kinds of stimulus at certain times and there are "windows of opportunity" for learning or emotional attachment that must not be missed.

Bruer's expert opinion will doubtless come as a relief to parents fearing that the 5-year-old they've adopted may be beyond hope; it should also give pause to the yuppie couples frantically waving flashcards and playing Mozart tapes to their toddlers. But the myth of the first three years has also done much good. It has helped persuade a mean-spirited Congress to spend money on programs benefiting America's youngest children.

This book is narrowly focused on neuroscience, and gives little hint that illuminating work on how children learn has been done in other disciplines. Page after page is littered with images of blinded kittens and mutilated monkeys. Yet Bruer concludes that at this point neuroscience can tell us little about how to raise our children: "Parents should realize that children thrive in a wide variety of physical and cultural environments and learn and benefit from experiences throughout their lives." Even for readers uninterested in animal rights, this might seem a lot of suffering for such fragments of knowledge.

Meticulously researched, combining charm and erudition, humor and humanity, The Scientist in the Crib: Minds, Brains, and How Children Learn, by Alison Gopnik, Andrew N. Meltzoff and Patricia K. Kuhl (Morrow, $24), should be placed in the hands of teachers, social workers, therapists, policymakers, expectant parents and everyone else who cares about children. Gopnik and Meltzoff, who are both psychologists, and Kuhl, a leading expert on language development, utilize psychology, philosophy, linguistics, poetry and personal observation to reveal how babies and children think. They explain that study of the child's mind has been aided by the advent of two marvels of modern technology: the video camera, which allows for unique experimental structures, and the computer, which provides both a metaphor for the brain and a working -- though highly simplified -- model of it.

Babies come into the world already knowing a lot -- that other people are like themselves, for instance, and what all the languages in the world sound like -- and with brains that are receptive to precisely the kind of experience and input they're most likely to receive. They are extraordinary and determined learners. And from parents, siblings and other caregivers, they encounter exactly the kind of teaching they require.

This book is full of enchanting revelations. Babies identify with other human beings at birth, for example, and assume their own feelings are universal. But at around 18 months of age, they realize that other people have preferences and desires that differ from theirs. "The terrible twos seem to involve a systematic exploration of that idea," write the authors, "almost a kind of experimental research program . . . For these two-year-olds, as with scientists, finding the truth is more than a profession, it's a passion. And, as with scientists, that passion may sometimes make them sacrifice domestic happiness."

Despite the off-putting hint of self-pity in the title, there's some cogent and compassionate observation in The Orphaned Adult: Understanding and Coping With Grief After the Death of Our Parents, by Alexander Levy (Perseus, $24). Levy points out that the loss of our parents -- how and when they die, the state of our relationship with them at the time of their death -- has a huge impact. A parent's death can modify or redefine all our remaining years, and we grieve as deeply -- if not more so -- for parents we hated and feared as for those we tenderly loved.

"There is no experience quite as stunning as when there is nothing where something has always been," Levy writes. Levy's own father died of a sudden and unexpected illness; his mother, frail and demented, wandered into death over four seemingly endless years. Remembering, Levy sees that he doled out his attention to her "more and more parsimoniously, as it began to look like her decline would never end."

He describes the heightened awareness of mortality that follows, particularly, the death of the second parent: the crisis of identity and faith, the loss of all sense of mooring and home. Yet parental deaths, because they are seen as natural and inevitable, seldom earn those who suffer them much empathy or understanding.

Many people find that, oddly, the emotional relationship with a parent continues to change after the parent's death. Sometimes a parent is by turns demonized and idealized. There are revelations when the living child has a child herself, or passes the age at which his parent died. Often -- though it's seldom noted in the literature -- a kind of elation follows parental death. It frees us from the parent's criticism and dissatisfaction, from labels inflicted on us in childhood that have continued to define and bedevil: the intellectual sister, the responsible older brother, the charming but scatty little one.

The beginning of The Orphaned Adult is particularly strong, as are the admonitions not to oversimplify this complex and universal human experience. But some of Levy's observations are simplistic: for instance, his division of adult life into distinct stages, depending on whether both parents have died or only one. And the little homilies, so typical of advice books and featuring Patrick and Richard and Rachel, are jarring. There's also an odd omission: In a deeply personal book, Levy seldom stops to wonder what the effect of his own inevitable death will be on his children.

"An aged man is but a paltry thing," W.B. Yeats memorably observed, "a tattered coat upon a stick, unless/ Soul clap its hands and sing, and louder sing/ For every tatter in its mortal dress."

The astonishing thing about The Caregiver (Steerforth, $21), in which Aaron Alterra describes tending his wife, Stella, as Alzheimer's takes away more and more of her memory and sense of self, is the author's complete lack of self-pity. There's no posturing, no self-congratulation for giving up his life to care for her, no ranting against fate, no whining about fairness. Only the facts, carefully arranged, sparely and beautifully written.

At one point, Alterra pays tribute to John Bayley's Elegy for Iris. Pre-empting our questions about his own situation, he speculates that readers of Elegy might wonder at Bayley's devotion to his failing wife, thinking: "Couldn't he afford better alternatives? How could he not prefer a night at the theater with old friends to sitting alone reading while she slept in another room?"

Alterra knows the answer: "He loved the girl. That is what love is for him. It was not a duty but a grace to be a presence to her as she was to him; to be all the memory she had . . . "

Unlike Iris Murdoch, Stella seems reasonably placid. She smiles. She tells Alterra frequently that she loves him. But he understands that, given the irrational movement of ideas and images through her mind, she would probably barely notice if he were gone. Still, he hopes to outlive her "simply because I can do more for her than anybody else, even though she might not feel very profoundly or for very long the loss of whatever that is."

Ultimately, though the book may also serve as a useful guide for Alzheimer's families, this is the great strength of The Caregiver: It shows us what love is, at the core and stripped of hope and illusion. It tells us what it means for soul to clap its hands.

Juliet Wittman is the author of "Breast Cancer Journal: A Century of Petals."