At first, the famous neurologist and author Oliver Sacks hangs back like a shy animal. It is Kate Edgar, his down-to-earth editor and assistant, who strides across the common area of a bright suite of offices in downtown Manhattan, greeting PW and gently insisting that we take her green fleece jacket to swaddle ourselves against the blasting air-conditioned cold of Sacks's own office. Sacks watches from a distance.

Dressed in a green T-shirt and khakis, his 68-year-old body looks robust and powerful, yet the man inhabiting the rugged frame looks as earnest and as excruciatingly vulnerable as Robin Williams's portrayal of him in the movie version of his 1973 book Awakenings, which chronicled the brief chemical resurrections of an extraordinary group of people who had spent decades frozen in trance-like states following bouts with sleeping sickness.

In light of recent events, it is relevant to note up front that the sensitivity and intense attentiveness that are so visible in Sacks are gifts that were greatly shaped by the trauma of war. Suddenly, it is easier to understand why Sacks, who was born in London in 1933 and received his medical training at Oxford, chose to believe the nurses at Beth Abraham Hospital in the Bronx when they reported that there were feeling and thinking individuals buried beneath drastic parkinsonian symptoms that made the post-encephalitic patients seem to be the living dead. Sacks, a consulting neurologist, decided to administer L-dopa, a drug proven effective in treating Parkinson's, to try to bring these people back partly because he remembered what it was like to be six years old and shipped out of London with his 11-year-old brother to escape the bombing. In his new memoir, Uncle Tungsten: Memories of a Chemical Boyhood, published this month by Knopf, Sacks relates that after years of beatings by a sadistic headmaster, years of loneliness and fear, his brother Michael broke down.

"This is something I don't go into [in the new book] but when my brother Michael had his breakdown and became psychotic, one of the things he said was, don't call this a disease. It is my struggle, my world, my attempt to find meaning," says Sacks.

Sitting across from PW at a big, blond-wood desk in a bright office, he speaks softly and in rapid bursts of thought.

"Let me show you something."

He jumps up abruptly and leads PW into the office kitchen to point out a cupboard blazoned with little illustrations of great chemists from the last three centuries. Just as in his memoir, Sacks rushes to counterbalance his pain with the seemingly indestructible order of science, especially prequantum chemistry. In 1945, when Sacks encountered a vast representation of the periodic table at the just reopened Science Museum, he declared it the most beautiful thing he had ever seen. It was evidence of a divine order that "was neither arbitrary nor superficial, but a representation of truths which would never be overturned...."

Sacks admits that there is tenacity in him, a drive to investigate and not to be turned away until he has found the deeper truths, the person, under the disease. Awakenings was declared a masterpiece of medical writing by W.H. Auden, winning comparisons to the writings of the great Russian neurologist A.R. Luria and to Sigmund Freud because it brought the case study to the level of art. Literary and beautifully described, Sacks's portraits conveyed truths that were greater than a sum of symptoms. In Awakenings, as in his other books, including the bestselling The Man Who Mistook His Wife for a Hat (1985), An Anthropologist on Mars (1995) and most recently The Island of the Colorblind (1996), Sacks "makes housecalls at the far borders of human experience" to send back exquisitely detailed reports about our drive and the capacity to be individuals in the face of impersonal and seemingly insurmountable forces.

Along with Auden, Sacks credits both his parents as sources of inspiration; both were doctors and great storytellers. His father made house calls, and an essay pressed upon PW in the course of our interview describes how Sacks virtually co-wrote Awakenings with his dying mother. She would lie in bed and listen and ask questions as he told the stories of his brave and unique patients.

" 'That doesn't ring true,' " she would say," Sacks remembers, telling PW that he would rethink and rework until he heard her say, "Now it rings true."

Back home from his hellish boarding school, the city of London itself became a teacher. As the bombs fell and familiar landmarks and beloved sights disappeared, Sacks developed a passion for journal keeping and for photography.

"Such documentation was, in part, forced on me by the war, the wholesale way in which seemingly permanent objects were destroyed or removed," he writes in the book.

This documenting marked the beginning of what would be an abiding interest in perception, memory and identity. The disappearance of things also increased his need to study old books and fossils and old things of all sorts. He still loves and surrounds himself with primitive things, elemental things, invertebrates rather than vertebrates, ferns, minerals, metals.

When we comment on a shelf of books by his friend, the marine biologist and artist Richard Ellis, Sacks jumps up and races out of his office and returns with two rubber-toy versions of the giant squid prepared for display in the Museum of Natural History by Ellis (little toy cephalopods also adorn the bathroom).

"I like this idea of the truth of being," he says, echoing a phrase PW comes up with for the way he obviously delights in physical things, objects and in the sense of physical movement. He still swims two hours a day, and even when he isn't making his house calls all over the globe (he is leaving for Guadaloupe the next day), he is in movement.

"I need the physical," he says. When he was an intern in California, he lifted weights, owned a motorcyle and hung out with the Hell's Angels.

"I used to travel immensely on the Norton," Sacks reminisces. "I would leave UCLA on Friday afternoon and go to the Grand Canyon, traveling 900 miles on Route 66. It was that feeling of your hair blowing back....It was, as you say, embodied."

And now there is the swimming. As he put it in an essay in the New Yorker, there is a joy, "an essential rightness about swimming, as about all such flowing and, so to speak, musical activities."

Writing, surprisingly, is not always a joyous flowing activity for the productive Sacks. Indeed, he has destroyed or lost so much work that Kate now copies everything before it leaves the office.

Writing his first book, Migraine, was a battle outwardly as well as inwardly. When he wrote it in 1967, his then boss literally locked up the manuscript, threatening Sacks that he would never work in neurology in the States again if he presumed to publish. Even his father, to whom he had gone for counsel, warned Sacks not to cross this powerful man.

"I think my father was a man who combined, as I do, great timidity with great courage," offers Sacks.

In September of 1968, however, unwilling to be bullied into silence, Sacks gave himself 10 days to reconstruct the book, or, he vowed, he would kill himself. The book flew out in nine days of nearly round-the-clock work. After Sacks dropped it off at Faber & Faber, he walked through the British Museum, filled with the feeling that he had made something, "something outside myself which could no longer be destroyed by me or anyone else."

Waiting at home in London to be interviewed on the day a glowing review appeared in the London Times, Sacks remembers, his father came into his room "pale and shaking, at seven in the morning, saying, in a horrified tone, 'You're in the papers.' "

"For years I automatically substituted the word 'publish' with 'punish,'" says Sacks. "For whatever reason, both my parents had the feeling that one ought to lie low."

When Oliver Sacks was 14 years old, his mother, a general surgeon and professor of anatomy who moved her practice to gynecology and obstetrics in the 1930s, arranged with a colleague, a professor of anatomy at the Royal Free Hospital in London, that he should be inducted into human anatomy by dissecting the body of a 14-year-old girl.

"Some of the girl had been dissected already, but there was a nice, untouched leg I could start on," Sacks writes in his memoir.

It took Sacks a month to dissect the leg. There were moments when Sacks could share his mother's feeling for how beautifully the organism was put together. Most of the time, however, his appreciation for the intellectual and aesthetic pleasure his mother took in anatomy was obliterated "in the horror of the dissection." Worst of all, "the feeling of the dissecting room spread to life outside—I did not know if I would ever be able to love the warm, quick bodies of the living after facing, smelling, cutting the formalin-reeking corpse of a girl my own age."

"I don't think there was anything sadistic or perverse," he tells PW. "I think that she was carried away by enthusiasm and by love for her youngest and perhaps brightest son. I think she somehow wanted me to join her, and there was a failure of empathy or an identification, a forgetting that I was a fragile boy."

Still, it gives one pause to consider A Leg to Stand On, a book wrenchingly difficult to complete. Published in 1984, it is an account of a 1976 mountaineering accident that left Sacks's knee twisted and badly damaged. Even after surgery repaired the ligaments and tendons, the leg still felt alien and detached. Sacks had lost the inner sense of his own limb. Significantly, Sacks found he could write that book only as he swam. He would emerge dripping from a lake to scribble every half hour or so, until he had produced a manuscript of 300,000 words or so, written in running ink. He submitted it to his editor at Summit, Jim Silberman, who fortuitously hired Kate Edgar to convert it to typescript.

Asked if he writes with his mother or his father in mind now, he concedes that this "is a really interesting question."

"I don't consciously have anyone in mind," he says, "though it astonishes and moves me when people come up to me and say, 'I became a medical student because of you.' So it's not just mother but also them."

A bit later he adds that Auden and Luria were important father figures, adding that he still looks for father figures, although he is a "father figure if not a grandfather figure" himself.

"There is the paradox that you can find father figures and mother figures that are younger than yourself," he says with a kindly smile. "Which is what you do because it is what you have to do."

This simple statement acquires a special resonance after the recent attacks in New York and Washington, merging with Sacks's image of falling in love as a boy with one of the "giant barrage balloons which floated overhead in wartime London, looking like vast aerial sunfish, with their plump, helium-filled bodies and trilobed tails. They were made of an aluminized fabric, so they gleamed brilliantly when the sun's rays hit them. They were attached to the ground by long cables, which (it was thought) could entangle enemy warplanes, prevent them from flying too low. The balloons were our giant protectors as well."

Sacks admits that he does like to write with people nearby, with the background music of cheery conversation at a cafe or with Kate Edgar and the others working in the next room.

"I do have a fear of disappearing," he says softly.