Some time in the early 1970s, when my parents were living in Cleveland, they bought tickets to a George Carlin performance. They'd always liked his offbeat stand-up routines and genial guest-hosting gigs on "The Tonight Show" and figured they'd enjoy him live. I can still hear the shell-shocked sound of my mother's voice when she reported on their night out. "You wouldn't believe the things he said," she told me. "We must have been the oldest people there."

Carlin, who died Sunday of heart failure at age 71 in Santa Monica, left his indelible mark by trampling conventions, making everyone from middle-aged couples to Supreme Court justices squirm. For half a century, he battered away at hypocrisy with the unfettered glee of a clever teenager and the verbal mastery of a modern-day Jonathan Swift. He was a '60s-style rebel whose subversiveness was never a matter of passing subject or style. He was as hard on religion and euphemistic language as he was on Richard Nixon and pro-life conservatives. He remained, with a consistency few of his colleagues could match, very funny about a whole lot of things for a very long time.

Carlin never lost his ability to simultaneously startle, provoke thought and charm audiences across the spectrum. He never got stale or simply repackaged old ideas in new wrapping. My parents weren't alone in feeling thrown back on their heels. Even listeners much younger than him could feel challenged to keep up with Carlin's febrile, high-velocity humor.

"I have no regrets in life," he wrote in his 2004 book, "When Will Jesus Bring the Pork Chops?" "Although I am kind of sorry I never got to beat a man to death while wearing a tuxedo." Carlin crossed the political and the surreal, the momentous and the trivial and did it all with the easy, boundless invention of a jazz musician. Just hearing the sound of his gravelly voice made audiences perk up and listen more closely. Only someone who worked hard at what he did could have made it seem so natural and effortless.

Carlin's themes were the timeless ones of any great satirist - the chicanery of the powerful, the gullibility of the little guy and the importance of shouting back as loudly and artfully as possible. Most famous for those infamous "Seven Words You Can Never Say on Television," which led to a Supreme Court case on broadcast obscenity, Carlin became an enduring icon of free speech.

Crossing the line

Flouting the taboos on sanctioned dirty words was only the most familiar tip of the iceberg. The enduring achievement of Carlin's comedy and his importance as a social critic were rooted in a deep-seated Orwellian understanding of language as both a dangerous agent of control and a liberating force that had to be deployed in a fearless, tireless way. "I think it's the duty of the comedian to find out where the line is and cross it deliberately," he once said.

Carlin could be quotably epigrammatic, but you had to witness his bravura routines to feel the full impact of what he did. In "Religion Is Bull-," which soared past 1.6 million views Monday on YouTube, Carlin built a scaldingly skeptical case against some "invisible man living in the sky" who was full of commandments and potent threats about the multiple miseries of hell. "But he loves you," Carlin added, with unctuous sarcasm. "And ... He needs money."

"Life Is Worth Losing," a 2005 HBO special, opened with a hyphen-rich, heroic poem to rival any rapper's verbal dexterity. "I'm a high-tech lowlife. A cutting-edge, state-of-the art, bicoastal multitasker, and I can give you a gigabyte in a nanosecond. I'm new wave, but I'm old school; and my inner child is outward bound."

Carlin is often linked with Lenny Bruce, whom he regarded as an inspiration and influence, and Richard Pryor. His own insurgent, barrier-breaking comedy and keen eye for the oddities and absurdities of everyday life paved the way for everyone from Andrew Dice Clay and Sam Kinison to Jerry Seinfeld and Sarah Silverman. The remarkable thing about Carlin's longevity is the sustained focus on stand-up. While he did do some movies ("Car Wash," "Bill & Ted's Excellent Adventure," "Jersey Girl") and ventured into children's television, as the soothing narrator of "Thomas the Tank Engine & Friends," Carlin made his living, year after year, decade after decade, by standing onstage alone and making people laugh. He often made them uncomfortable and uneasy, but he made them laugh.

Hippie dippy weatherman

In his early days on television, Carlin did characters and set parody routines. There was the Indian Sergeant, an assortment of disc jockeys and hippie dippy weatherman Al Sleet. By the time my mother and father caught him in Cleveland, Carlin had morphed into the long-haired free spirit with a beard, an earring, too many drugs and a bellyful of bile about America in the Vietnam era. Thirty years later he was still shooting with dead aim.

"I hope you good, loyal Americans understand that in the long run the Islamist extremists are going to win," he told his post-9/11 listeners. "Because you can't beat numbers, and you can't beat fanaticism - the willingness to die for an idea.

"A country like ours, preoccupied with Jet Skis, off-road vehicles, snowboards, Jacuzzis, microwave ovens, pornography, lap dances, massage parlors, escort services, panty liners, penis enhancement, tummy tucks, thongs and Odor Eaters doesn't have a prayer - not even a good, old-fashioned Christian prayer - against a billion fanatics who hate that country, detest its materialism and have nothing really to lose."

That's vintage Carlin - the insinuating cordiality, the declarative certainty, the comic-heroic catalog and the sly twist that threads Christian prayer into this desert storm warning on Islamic extremists. It's fatalism served up with a smile. Or is it a grimace? The perpetual spark plug of Carlin's comedy was never quite knowing where or how anything might land.

About five years ago, I happened to be seated behind Carlin at the Curran Theatre. When I sat down, I remember thinking that Carlin had had his troubles with drugs and alcohol, that his wife of many years had died of cancer and that he was very much looking his age.

Then when the show started, Carlin snapped on. Intently focused on the stage, he sat with his back lifted away from the seat, his head hardly moving. He was like a human camera, registering every detail. It must have been a reflex for Carlin whenever house lights went down and a stage lit up. Something important, something worth watching and hearing very closely, was about to happen.

In November, Carlin will be remembered once more onstage, when he receives, posthumously, the Mark Twain Prize for American Humor at the Kennedy Center in Washington, D.C. "Thank you, Mr. Twain," Carlin said when he learned of the honor. "Have your people call my people."

E-mail Steven Winn at swinn@sfchronicle.com.