Somewhere in the deeper recesses of Rockefeller Center, in a modest office dominated by a full-length mirror, two questions loom above all the others: What can be known? And how can Phil Donahue know it?

Then come all the others.

"Homosexuality? Maturation? How do I raise a kid who's well-balanced, who's able to control anger? . . . 'I think, therefore I WHAT?' . . . Who presumes to have a special insight into the 'theo' of theology? Should there be an 'ology' at all? . . . Is this NOW or is this THEN? Or what's NOW?"

And, most intriguing of all, why has the platinum-maned talk-show host, the patter-familias of morning television -- the very same who received the Arthur Bell Award ("for his contribution to increased social understanding of the gay and lesbian community") at the Waldorf Astoria last night -- given birth to a weighty, 412-page tome called "The Human Animal," treating everything from natural selection to Nicaragua, hydrogen to the hypothalamus, testosterone to "The Texas Chainsaw Massacre" as it plumbs the eternal mysteries: "Who are we? Why do we behave the way we do? Can we change?"

Can we talk?

"I figured I'm out on a limb here," Donahue says, swaying precariously in his chair. "I don't have the academic credentials. I knew that one of the vulnerabilities here -- right off the bat we acknowledged, and I gave everybody permission to share my anxiety by saying aloud -- that one of our problems here is I don't have the academic credentials that Carl has for 'Cosmos.' Abba Eban I'm not, I would say . . . But I tell you this, I'm proud to claim paternity on this thing, and I see myself as very fortunate. This is the most exciting intellectual ride I've ever taken."

There's wisdom here. Let's listen to the wisdom.

Suppose that I, Phil Donahue, could reproduce myself the way blue-green algae do -- asexually -- without the participation of another of my species. The result would be a hundred or a thousand or a million Phil Donahues, all exactly alike. Clones. Perhaps a flattering prospect for me, but rather limited and selfish as far as my species is concerned. -- "The Human Animal"

The atmosphere in the room is dizzily Donahuesque.

Tieless and blue-jeaned, he sits still, more or less, when not turning to watch C-SPAN on his office TV. Today he's doing back-to-back shows (mercy killings and fat kids), meeting with the producers of a television documentary series, arranging the next day's show in Cincinnati and the following week's sojourn in Hollywood -- and taking important calls.

Call No. 1, from a famous sports oracle: "Yes? Hi, Howard. You don't sound like Howard . . . (This is Howard, I hate to . . .) HI, KID! YOU'RE THE GREATEST IN THE BUSINESS! I owe you a visit in October, isn't that what you wanna do? When's the book in the store? Uh, what's the title, Howard? 'I Never Played the Game.' This better be good . . . What's your secretary's name? I'm gonna have my people call Melanie and we'll work this out . . . I'LL TELL YOU THIS, KID, YOU'RE A STAR!"

Call No. 2, from a famous politician: "Reverend Jackson? Reverend Jackson? YOU LIKE TED KOPPEL BETTER THAN ME? . . . Huh? . . . Well why didn't we? . . . But I . . . But that's when you did 'Nightline' . . . Listen, I'm teasing ya. If you're gonna do anything and it ain't gonna be me, I can't hold it against you for doing that program. NOW WHAT ARE WE GONNA DO? ARE YOU STILL AVAILABLE TO US?"

Donahue sighs as he hangs up the phone. "He's kinda pouting," he says of Jesse Jackson. "He goes up and down. He's a great kibitzer and then he gets, well, he's in a 'serious' mode now."

Even in conversation Donahue is everywhere at once, dashing from Darwin to Freud to Jesse Jackson as if they were sitting expectantly in his studio audience and he, lunging with a hand-mike, has only a minute to get them on.

"This odyssey," he dubs his latest project, which includes a five-part science series, three years in the making and also titled "The Human Animal," to be aired sometime next year on NBC. "Donahue's effort to share this head-scratching thing," he elaborates, slipping comfortably into the third person. "Donahue's attempt to go even further than the kinds of discussions I'm very proud to be able to preside over on my show," he adds, not bothering to catch his breath.

Instead, he flaps his arms as if trying to become airborne, launches a missile at the general topic of Creationism and rides it into orbit.

"Here's all of life. And here WE are, somewhere out there, hanging out there where God came out of the sky and that's, you know, these people are saying, 'If I were God, this isn't the way I'd do it.' And I think it's KILLING us. IT'S LITERALLY KILLING US! And, you know, look, we're not gonna save ALL the babies, but I think we can save more than we are. And that's why we're here." He stops suddenly, turns blush-red and shifts uncomfortably in his seat. "I'm sorry. I think I'm talking too much. Go ahead."

Donahue breathes.

"I found out a long time ago," he confesses, "that the people who are least in command of their own material are the people who talk the most. It's true with me." Then, in a disarming burst of self-parody, he delivers what he calls his "big, arm-waving speech," an avalanche of emphatic sentence fragments piled one on top of another.

"This is CRAZY!" he shouts, banging on the desk. "We're WALKING AWAY from, LOOK what's OUT there! LOOK what we KNOW! We're not SHARING, if there's EVER a time when we NEED it, WE GOT KIDS OUT THERE! If a CHILD is born and he hasn't had THESE GOLDEN RINGS and he's, and you know, he's NATURALLY ENDOWED to REACH for it! There's TOO MANY BABIES being born who don't get, YOU CAN'T DO THAT TO A CHILD! They're HURTING! THE PAIN OF NOT FEELING WELCOME! AND-AH!-NA!-NA!-NA!-NA!-NA! -- "

He's gone into verbal meltdown.

In other words, our brain is a delicate hothouse flower that needs rich soil, just the right atmosphere, and the right balance of nutrients to flourish. But in a world of tedious jobs, free time, and personal stress, the brain is alternately overstimulated and understimulated. What happens when the brain, like a sick flower, starts to droop? -- "The Human Animal"

"I think he's an absolutely astonishing person," says Steven Naifeh, one of two writers hired to toil on the book using transcripts of the interviews Donahue conducted for his TV series. "I came away with a profound respect for his intellect and his ability to cut through the jargon and get to the point. I don't see him giving a graduate seminar on neuroscience, in which he dissects brain cells with his students, but I can easily see him giving a graduate seminar on behavioral science and its relationship to public policy."

"He's a very good interviewer; he asks one question at a time," says the oft-questioned sexologist John Money of Johns Hopkins University, who is oft-quoted in the book. "He has a good grasp of basic concepts and basic principles. One of his chief assets, as I think everyone knows, is that he opens up subjects right on the edge of Pandora's box."

"Calling Phil a 'talk show host' is like calling 'Death of a Salesman' an MOW [movie of the week]," says his second wife, actress Marlo Thomas. "He's reading and thinking and pondering all the time. When we go away on trips, I'm reading escape novels and Phil is reading books about the body and the mind and the behavorial sciences."

"The Human Animal," for which Donahue discovered Darwin's "On the Origin of Species" ("I actually have read it. It's not easy"), is replete with glossy paper, color photos of the author in various poses around the world, and testimony from scores of prominent behaviorists ("The Bible says God made Eve from Adam's rib. But, according to Dr. June Reinisch . . ."). Simon and Schuster has shipped out 100,000 copies, the book has climbed onto the national best-seller lists, and reviews have run the gamut from Time magazine's "Can we change? Of course we can. All it takes is a little finger pressure and zap! we are on another channel," to The Village Voice's "You have to give Donahue credit for encouraging open-mindedness."

"Marlo thinks I'm a good writer," Donahue says. "Marlo made me feel very good about my writing skills. But I'll tell ya this, if I'm conscientious, I will write, sleep and rewrite the next day. 'Cause my first go usually is language overkill."

This second opus, however -- unlike the first, his bestselling autobiography "Donahue" -- is largely the work of others, owing to his frenzied schedule as a multimedia phenomenon.

"I had final cut," he says. "I have to say, I didn't do a lot of wholesale changing. I did arrest some things, rearrange some things and rewrite some things. I was especially concerned about the captions. We spent a WHOLE DAY IN A ROOM WITH NO WINDOWS at Simon and Schuster going over captions because I think that's what most people read first. I wanted the caption to be a kind of hook to invite the reader in to check the text."

To wit, accompanying one photo display: "Why is it that we find one person more physically appealing -- more attractive -- than another? Why are some people attracted to hairy chests, others to blond hair, others to legs or bosoms or buttocks? Men's and women's rear ends, Manhattan Beach, California."

"This was an AGONY assembling this," he says. "You can do sexual reproduction and how we moved to sex and selected for sex because of variety -- that's kind of nice and neat and I had a great time with that -- but, you know, the difference between men's and women's brains? The difference between intuition and, you know, HOW MUCH DOES TESTOSTERONE MAKE A CONTRIBUTION TOWARD MALE AGGRESSIONS? You can make people crazy with this."

The man's outward energy suggests that his glands are perpetually churning.

"It came to me when I was just looking at movies," he says. "The curtain started to raise on male behavior. Almost all spontaneous violence and war and crime is male. You put a bunch of males together, according to Lionel Tiger, something is gonna happen. And then you throw in a six-pack, and then a FLAG, and a TEAM and a COUNTRY and a SECTION and a TERRITORY and MALES UNDER 30, and somebody says something about somebody's MOTHER, and there goes the WHOLE DAMN NEIGHBORHOOD.

"I've been to some Shea games this year, upper deck, THESE GUYS WITHOUT THE SHIRTS. Show me a fight at Shea, and I'll show you 20- and 19-year-olds. If you can get the male to 30, he's more likely to flee than fight. I mean, 35-year-olds can hurt you, but not as often.

"You and I can get INSANELY AROUSED and do some pretty good damage with our fists, but sooner or later we're going to become exhausted and look over our bloody selves and walk away. We're NOT going to kill each other. In the lizard, or even in the rattlesnake, the vanquished rolls over and urinates, and that's it, or exposes the neck and THAT'S THE END OF THAT. Now we have an enlarged brain which allows us to create instruments that go BOOM! NOW YOU'RE DEAD before the natural endowment of not-killing-you kicks in.

"If there was ever a time to really be curious about why we're behaving this way, it should be NOW, you know. NO OTHER SPECIES BEHAVES THIS WAY. It's really quite remarkable. No nation seems to have a national purpose UNLESS IT'S WAR. This isn't about scolding or anything, it's about asking why, and it's not presuming necessarily to have answers in tablet form.

"We have free will. But we cannot get away, we cannot ignore the fact that we are, HOWEVER MAJESTIC, we are also ANIMALS. And these are constraints imposed on us by our biology and WE SHOULD NOT BE ASHAMED TO EXAMINE THEM.

"As long as you fail to appreciate our part in THIS MAGNIFICENT DRAMA CALLED NATURAL SELECTION, as long as you believe we're especially created, something outside that, we're DOOMED to never really get anywhere in an appreciation of who we are, never turning our kids on to this and diminishing the chances of future Darwins and Freuds, I'M ALMOST FINISHED, the, the, uh, well . . . "

And then he is finished, if only for a moment.

According to one theory, within the hypothalamus is an area called the "sex nucleus," the seat of many of the sex differences between men and women. If she finds the guy attractive, the theory goes, the sex nucleus transmits a message, by way of chemicals called releasing factors, to the tiny pituitary gland, which acts as a kind of outlet store for the hypothalamus. -- The Human Animal

Perhaps the hypothalamus is talking to the pituitary when, during the taping of the fat-kids program, Donahue touches the hand of one of his guests, a slender child nutritionist, and she reflexively traps his hand in both of hers, giving it a brisk massage before letting it go.

"Women like him because I think what they see is a very open-minded man," says Marlo Thomas. "Really I think that's it. Erma Bombeck once said men in the public eye represent certain things to many people -- John Kennedy was like a brother figure, somebody else might be a father figure. And she said Phil was a husband figure. The thick white hair doesn't hurt."

A celebrity feminist in the formative years of the women's movement, Thomas argued during the preparation of "The Human Animal" that "for every male anthropologist, they should talk to a female anthropologist, for every male behaviorist, there should be a female behaviorist."

Donahue, a famous convert to the cause -- as chronicled in his autobiography, which dissects his failings in a first marriage that produced five children -- clearly took the advice to heart. Indeed, his writers say he would sometimes caution them against insidious male chauvinism when they met to discuss the book-in-progress.

"Sure, I notice sexism," Donahue says. "I still have to work on myself. My sons can use words like 'chick,' 'broad,' 'fox.' And I go, 'What is a chick?' But I just think also that they're less afflicted than their father was at that age. I really see that. They appreciate women as people, more than I did."

Chastened but hopeful, he confesses to a litany of "continuing lapses": "I'm not as conscientious about birthdays and presents as Marlo is. That's not a big thing but it's a throwback to 'that's women's work.' I stack dishes instead of washing them. I still have to consciously pick up my own socks. I always drive. Well, not always. I'm improving on that, too."

His spouse elaborates, "It's just that he always insists on driving. He can't seem to find the hamper. The fact is, he knows he can't find the hamper. He knows it's dumb. A lot of things he's learned already. Phil does not see the bottle of dish-washing liquid. He sees only the faucet."

Happily, the couple has decided to put an automatic dishwasher in their Upper West Side apartment, an act presaging the sort of commitment to New York residency that encourages speculation about Donahue's political plans. One willing participant in the speculation is Donahue, who said last February on "60 Minutes," right after he moved from Chicago, that he'd like to be a senator.

"I don't know," he obligingly muses today. "I'll be 50 in December. I feel pretty good. I feel healthy. Would I, maybe around my mid-fifties, wanna do something else? Would I wanna do something in public service? I'm fascinated by what goes in your town."

He waves at the show on C-SPAN: a member of Congress industriously pounding a lectern. He watches for a moment and goes on, "I don't think that my ego and my emotional well-being are necessarily as bound up in HOW MUCH POWER I'm going to have, as it is in what I would see, if a Senate run would be my choice, as A TREMENDOUS OPPORTUNITY. You know, I'd like to be in the Senate. I remember sitting up in the gallery and looking down at all these blue suits. God, these guys spend MILLIONS OF DOLLARS to get here. THIS MUST BE A HELLUVA JOB! "There's a down side to this, too. I mean, I WANNA BEG FOR MONEY? DO I WANNA? You know, this'll make people, especially the Washington mind-set, chuckle, but could you get elected being beholden to no one? WOULD THAT BE POSSIBLE? You know, I do have the good fortune of having a recognizable name. Presumably I wouldn't need the money that it would take for the advertising to gain that familiarity. IS THAT NAIVE?"

Donahue, who makes a point after every show of thanking his studio audience as it files out the door ("I had a good time, I hope you did. I'm glad you came"), would seem to be a born campaigner. And it's easy to imagine him giving floor speeches, interrogating subcommittee witnesses and running to quorum calls. It's somewhat harder to imagine him writing a tax bill.

"Phil is a pragmatist, and he has his finger absolutely on the pulse of the people," says the ex-producer of his television series, Adrian Malone, who made Jacob Bronowksi's celebrated "The Ascent of Man" and recently broke with Donahue over stylistic differences. "He is on the leading edge, if you like. But if you look at a Japanese samurai sword, the major force of the sword is the area behind the cutting edge. The cutting edge is easily blunted and changes its shape very rapidly."

It is barely 3 in the afternoon. But already it has been a full day, a day swirling with events and ideas, people, places and things; it is also election day in New York City, and so another question looms large on the landscape: Just how has Citizen Donahue exercised his franchise?

"I must not tell a lie. I didn't vote today. You know, I'm not even registered. Now remember, I just got here in January. But I'm ashamed to tell you, I have to say I saw Koch as a shoo-in and never really considered my own responsibility to make my contribution to this thing. It embarrasses me."

Embarrassment is a natural emotion . . . part of the biology of the human animal . . . having evolved through countless generations . . . of parents and children . . . male and female . . . in a magnificent drama called natural selection . . . as majestic as blue-green algae . . . as remarkable as a hothouse flower . . .

But certainly nothing to be concerned about for very long.