It's been a half century since a young firebrand named William F. Buckley Jr. burst onto the political scene with "God and Man at Yale," a scathing indictment of his liberal alma mater. By age 30, he had founded the conservative magazine National Review, which would become the bible of Ronald Reagan. By 40, he had his own television show, "Firing Line."

Buckley, virtually alone, was the public face of political conservatism in the 1960s and '70s. He made it intellectually defensible. It became popular. It even became sexy. And Buckley became a cultural icon.

The firebrand quietly turns 76 this year. "Firing Line" is gone after three decades on the air, the longest-running show with the same host in TV history. Buckley is off the lecture circuit he once rode to win converts to the right. He barely knows the current occupant of the White House, a self-described "compassionate conservative," having seen him "maybe two or three times."

New generations of conservative intellectuals now fill think tanks. They write for his National Review but also the Weekly Standard and the Wall Street Journal editorial page. "It's not lonely the way it was 45 years ago," Buckley says, "when there was really nothing, certainly no journal of opinion on conservative thought. There are tons of people here now."

So what's an icon to do? Buckley has returned to his roots, to the keyboard over which his fingers have long danced. Whether working out of his Upper East Side apartment in New York or the converted garage of his Stamford, Conn., home, Buckley is writing at a tremendous rate. He's writing e-mail--to friends, to fans, to foes and even, a few times, to the author of this article. He's writing letters. He's writing two columns a week. He's writing books at a pace of one a year.

And, of course, he's busy being himself--an urbane, charming sage. "He's being Bill Buckley 24 hours a day, and that's part of what his job is," says Sam Tanenhaus, who is writing a new biography of him. "That's not something you can retire from."

Time was, Buckley could be counted on to rise eagerly to every challenge in the political arena. But, like an aging lion, he isn't so easily drawn into battle these days. He no longer follows current events with the passion that he once did. He is, as one friend says, serene. Or, to use a word secure in Buckley's vocabulary, irenic. A promoter of peace.

But he can still mix it up. Consider Buckley's response to a review for his last novel, "Spytime: The Undoing of James Jesus Angleton." Some critics liked the book. But others didn't; and one, Eric Tarloff, was unusually blunt.

"Something must be said," Tarloff wrote in his review last year for the New York Times. The erotic scenes in "Spytime" are "like passion observed and described by an alien . . . exceptionally finicky life form." Tarloff treated his readers to a few of those scenes and pronounced them so bad "that they're far and away the most enjoyable part of the book, by themselves almost reason enough to justify a recommendation."

Now, it must be said that Tarloff knows something of this territory. In his first novel, "Face Time," Tarloff's protagonist is a presidential speech writer who is cuckolded by the president of the United States. In his second, "The Man Who Wrote the Book," his hero is an English professor who writes a dirty book.

Tarloff also couldn't be more different, politically, than Buckley. Buckley once raced to the defense of Joseph McCarthy's campaign against Communists in the U.S. government; Tarloff's father, a screenwriter, was blacklisted during the McCarthy era. Tarloff has been a speech writer for Bill and Hillary Clinton, and Tarloff's wife was once Clinton's chief economic advisor.

When Buckley sat down at his keyboard to reply, the result was stylish, tart and witty:

"Having egregiously misread the plot, Mr. Tarloff goes on to amply excerpt from erotic passages in my novel, on which excerpts I would comment except that merely to pass my eyes over them brings on such ardor as to leave me immobilized."

Buckley, smoking a Dutch cigar in his Manhattan apartment, chuckled as he recalled the letter. "Maybe I need to take a course in erotic writing," he says, arching his famous eyebrow.

Writing and language have always been Buckley's passion. He grew up in a house where erudition was prized. His father, an oilman, saw to it that the Buckley children learned French and Spanish from nannies and sojourns abroad. They practiced concertos at the piano and political argument at the dinner table.

By the time he turned 50, in 1976, Buckley was one of the 20th century's best-known public intellectuals, a Renaissance man of the right. He was doing his television show, lecturing across the country and appearing in debates on network TV. He had written nonfiction books about everything from politics to sailing, and his use of words--especially rare ones--sent readers and listeners to their dictionaries. As Samuel Vaughan, his editor, put it a few years ago: Buckley's use of language elicits "both exasperation and admiration."

It was also at age 50 that Buckley added two pursuits to his repertoire--he took up the harpsichord and became a novelist. He developed a passion for the harpsichord after his younger brother sent him one as a gift. But now it's the source of some regret. "I've performed nine times in public," he says. "But after the ninth time, I realized I was just not good enough. Among other things, I was so frightened--God, I was so frightened--that I made mistakes that I didn't make when I practiced. I just don't have the natural prowess. So I hardly play anymore."

His first attempt at fiction was more successful. As Buckley tells it, he was pressured by Vaughan into attempting a novel. "I told him how much I was enjoying reading 'The Day of the Jackal'--a terrific book--and Sam said to me, 'Why don't you write a novel?' " Buckley recalls. "And I said, 'Sam, why don't you write a trumpet concerto?' "

But a contract materialized the next day, and Buckley agreed to try it: 100 pages for one-third of the advance. The result was a bestseller, "Saving the Queen," the first of 10 novels featuring the dashing CIA agent Blackford Oakes (and Buckley's first sex scene, with Oakes taking a young Queen of England to bed).