If ever there was a "multiple personality," it is -- or they are -- Jonathan Miller, M.D.

Yes, the same Jonathan Miller who put his medical internship on hold for a few years in the late 1950s and early '60s to, as he puts it, "frisk about on a stage and do silly things." That was in a hit revue called "Beyond the Fringe," with Cambridge pals Dudley Moore, Peter Cook and Allan Bennett.

Yes, the same Jonathan Miller who left his medical practice, again, to direct plays (most recently Shakespeare's, including a controversial "Merchant of Venice") for the British Broadcasting Co. and to produce operas (mostly of the 18th and 19th century, including a controversial Mafioso "Rigoletto") all over the world.

Yes, even the same Jonathan Miller who produced the enormously successful TV series "The Body in Question" and wrote the book -- a humanistic history of medicine -- of the same title.

And now that same Jonathan Miller is once more practicing medicine -- neuropsychology -- and writing pop-up anatomy books for children and adults.

Two years ago Miller and designer David Pelham produced their first pop-up book, "The Human Body." Although they thought they were doing it for children, says Miller, "it crept into a lot of doctors' offices and an awful lot of adults got it for themselves." It sold about 800,000 copies. Now they have done it again with, mincing no words, "The Facts of Life."

With aplomb and the same lighthearted approach he took in "The Body in Question," Miller has provided what he calls a "broaching" point for parents to do what few can: tell their children about, uh, talk to them about, er, you know, um . . . sex.

Miller sees the book, colorfully illustrated with three-dimensional and movable parts, as "straightforward and all mechanical . . . I think parents often find it hard to speak to their children when they only have, as it were, the naked topic." The book is, he believes, "sensible and explanatory and decent, and you really can't ask for anything more."

Nevertheless, in a recent NBC "Today" show appearance, the compleat Englishman managed to all but shatter Connie Chung's chilly composure as he turned the pages of the book for the viewing audience. At one double-page demonstration of a giant sperm fertilizing an enormously magnified egg, Miller said, opening and closing the book to make the movable parts work, "This is action sperm, you see."

"Oh dear," responded Chung. "Indeed it is. Actually moving . . . It's really shocking, you know, when you first see it . . ."

He is not surprised that anti-abortion groups in this country are already using the book's lifelike illustrations of a developing fetus as evidence upholding their views. Although Miller himself tends to be dispassionate about abortion, he says that "in a way, I'm not altogether in disagreement with their reasons. The page of fetuses gives you pause. And actually, if the only reason why you didn't have pause was because you didn't know how the fetus looked, then it is certainly important that you should."

Next year's multidimensional production will be on the eye, but for now it is back to neuropsychological humanism and a staging of Mozart's "Don Giovanni." Word of Miller's retirement from opera was apparently somewhat premature.

It is altogether fitting that Jonathan Miller be concerned with the mind and brain -- and especially thought processes.

He is himself an elegant thinker, and a conversationalist beyond peer. He is possessed of intense opinions, and he expounds upon them in vivid verbal images, literary and poetic allusions in at least three languages, and pun after pun often whimsically set off with "as it weres."

As he speaks, the mobile face illustrates the flow of his dialogue, now pained, now amused, now exasperated, now delighted. And his hands -- dancing accompaniment to the voice and face as though choreographed by Twyla Tharp -- wrapping insouciantly around his head, pointing, waving, emphasizing this point, dismissing that, creating a whole of exquisite eloquence.

It is also fitting, then, that hand movements are something Miller is interested in studying -- "how they help speech, exactly how they are integrated into speech and what is their relationship to the timing, the stress patterns and the expressive patterns of speech." This began, of course, as a theatrical concern, but now it intrigues him "from the purely neurological point of view.

"We don't speak and then add a cabaret on top of the speech to make it more striking," he explains. "The act of wishing to make your meaning clear point, frown is an integrated gesture, grin neurological performance which, moving my hand, moving my head, putting the stress in the particular place, choosing the words that I am, all come in one thing. It is not like a sort of autoworks, where you put the motor on, then bolt the chassis and then put on the coachwork. Deciding what it is you want to say already presupposes that you have made a decision about the entire expressive apparatus you are going to employ in order to make that meaning clear."

There may be a "temperamental quality to the use of the hands," he says, "and then there are certain ethnic groups who make more of it . . . Perhaps it's because I'm Jewish, but I don't think so. It's just that I waggle my hands about a lot . . ."

This, of course, immediately brings to mind Miller's notable moment in "Beyond the Fringe," in which, waggling his hands and contorting his leggy, 6-foot-3 frame, he said, shyly, "You know, I'm not really a Jew . . . I'm just Jew-ish . . ."

Humor has been an integral part of his life, beginning with his teen-age years in London as a wartime radio comic. Later he specialized in natural sciences at Cambridge University -- where "Beyond the Fringe" was born -- and then became a Goldsmid Scholar at University College Medical School. He began his medical career as a pathologist in Cambridge, and in the mid-'70s won a fellowship in the history of medicine at University College in London. Most recently he spent a year in neurological studies in Canada.

Even with his patients, Miller says, he finds it perfectly natural to laugh and joke, but he is not necessarily always tactful -- a trait that may have endeared him to a loyal group of iconoclasts but has exasperated many others. He has never been timid about swimming against the tide, and he holds himself indifferent to the little eddies of controversy that follow both his medical and artistic personae.

His approach to neurology is quite outside the mainstream. While most researchers are working, as Miller puts it, "from the bottom up" -- beginning with the "neural structures" inside of the brain -- he prefers "the top down" technique. In other words, he is studying the brain by clinically examining brain-damaged patients. "It's rather like interrogating an espionage agent," he says. "You have to do it over days and days until they gradually give themselves away."

Miller altogether disapproves of current neurological dogma and inevitable "pop" versions of "Balkanizing" the brain "a la Shirley MacLaine and those people who squeal, 'Ooooh, I've got eight different parallel personalities who existed during the French Revolution all on the right side of my brain . . .' " He also spurns the sort of neurological work that involves "sticking needles in cells and looking at the electrophysiology . . . I'm much more interested in more detailed descriptions and philosophical untanglings of some of the problems of language and perception."

Miller's enthusiasms are infinitely eclectic, and he turns from a vigorous description of a seriously brain-injured patient to an equally vigorous attack on the way most productions of Mozart's "The Magic Flute" portray the Queen of the Night -- "Aztec Night at the Copacabana." In his own production she is the Empress Maria Theresa, and the opera is about light and reason and Freemasonry.

His lack of musical training -- he still doesn't read music -- did not inhibit him from taking on opera. (He was 40 when he produced his first.) He especially loves Mozart, and his upcoming staging of "Don Giovanni" will round out his productions of all the Mozart operas that "aren't boring": "the 'Don,' the 'Flute,' the 'Marriage' and the 'Cosi.' " Miller maintains that there are only 40 operas "where you actually know what to do because they are good stories and the music is consistently part of the drama.

"As for the rest of them, it's very good they're stuck in Italian and nobody knows what's going on."

Jonathan Miller lives in London with Dr. Rachael Miller, his wife of 29 years, who practices medicine full time with the British National Health Service. They have three children -- a daughter, 17, and two sons, 20 and 22.

He travels relentlessly -- he is a popular speaker -- and he sees America as his second country. Indeed, he has become a kind of latter-day Alexis de Tocqueville, absorbing, analyzing, cataloging, processing Americans and Americana.

Today the 50-year-old, trim and fit-looking Miller turns his full scorn on America's romance with fitness.

"I mean," he says, "I'm not against taking exercise, but I'm against the self-conscious taking of exercise, even if, in fact, it could be shown with the same sort of accuracy that the Surgeon General could report on tobacco that exercise lengthened life the way cigarettes shorten it . . . But as far as I'm concerned, running is something one undertakes for the purposes of either flight or pursuit, and there are very few things at my age that I'm keen on pursuing enough to break into a run, and so far nothing has pursued me which has made me want to flee with that speed."

He guffaws, then adds, "I cannot bear those self-righteous couples one sees in the park . . . jogging along together in some hideous partnership in health and perfection. God rot them, I say."

Although, on some things, he waits to be asked, his impressions fairly burst out of him when almost any subject is broached.

On the American political climate: "There is, of course a tremendous shift to the right, and a sort of crazy evangelical Christianity taking possession of politics in a way it wouldn't have done previously and certainly which it would never have had a hope of doing in England . . .

"You watch these people like Falwell and the preachers on TV on Sunday mornings, these double-breasted, white-suited maniacs holding this limp, floppy Bible in their hands, addressing crowds of 10- or 15,000 in a football stadium, and you wonder what on earth is going on."

He is wound up now, and not to be stopped.

"And then," he says, "there is this sort of stored turnip of a president . . . yes, an actor. I think you only need to be a modestly accomplished actor in order to be able to be president , and a bit player could probably do as well as he is doing, which is, after all, what he was . . . It is rather sad that we should have for the first time in history a bit president."

He pauses for a moment. "But I must say, one of the things you do meet across the country as I do, going from campus to campus, from bookstore to bookstore, you meet a thinly dispersed but totally continuous network of people who are in complete agreement that this is appalling. A literate, well-read world of decent liberals who are not vile leftist radicals, just concerned Americans who feel their country has been taken possession of by all sorts of waterlogged minds. And it's horrible."

On success and celebrity: "In America there is a huge endless cocktail party going on in the country's executive suite, one huge executive suite with no walls. Here you can have a Nobel laureate neurologist who ends up being the boyfriend of some New York socialite . . . Now that is really very peculiar, you see. You simply would not get that in England.

"The very idea of Torsten Wiesel a Rockefeller Institute Nobel laureate , who does very nice subtle work on the visual cortex which would never be understood by anyone in New York on that level, becoming a sort of social hero . . ."

He huffs. "I've never known a country so obsessed with success and celebrity . . . It's daft and balmy and degenerate."

Soon he is complaining that his visit to Washington is too short to let him get to the National Gallery, and at the last he wanders off briskly, a copy of "Meditations on the Life of Christ" tucked under his arm and one of "Facts of Life" in his briefcase. He may not jog, but, as he puts it, "I'd rather live my life than prolong it. It's hard enough to squeeze through the brambles of life as it is."