There I was, carefully underlining sentences in the scientist Carl Sagan's Dragons of Eden on a bus replacement service from Swansea. I read of the R-complex, the reptilian core of the human brain, and immediately knew that comic material lay within. By the end of the journey, I had come up with what I believed would be the greatest R-complex routine ever performed. I proudly ring my friend Carl with news of my groundbreaking evolutionary comedy routine. "George Carlin's done that already," he says, "and it's brilliant, much better than yours."

George Carlin on religionAt the BBC I sat writing what I believed to be the best sketch I had ever written, about a paranoid man who worried that everyone had more stuff than him. "You're writing a sketch about 'stuff', what's the point?" Carl asked when I told him. "George Carlin wrote the best routine about that ever."

Last week I spent the night carefully constructing a routine about a government's fear of an educated population. I sit down with Carl for a cup of coffee the next morning. He puts Carlin's latest show on. You can guess the rest.

If George Carlin tackled a topic, it stayed tackled. The ground was his. Carlin began his career in the mid-1950s as a conventional gag-teller. It was seeing Lenny Bruce in 1962 that changed everything; he saw just how powerful a lone figure talking in a club could be. That night in Chicago Bruce was arrested for obscenity, something to do with Christ and Moses. Carlin shared the police wagon with Bruce after refusing to show his ID to a policeman.

Later Carlin said: "Lenny Bruce was revolutionary because he brought honesty into a form which previously had been little more than empty crowd-pleasing. He made being full of shit old fashioned." Carlin grew his hair, and got honest. He gave full rein to his scorn - for authority, for platitudes ("It's called the American Dream, because you have to be asleep to believe it") and for the public. The public loved it.

One of his favourite targets was the hypocrisy of censorship: "You can say I pricked my finger," he noted, "just don't say you fingered your prick." Unsurprisingly he got in trouble: he was arrested for obscenity in 1972 after performing "Seven words you can't say on TV" at the Summerfest in Milwaukee. Who knows which word upset off-duty policeman Elmer Lenz most - shit, piss, fuck, cunt, cocksucker, motherfucker or tits. The resulting case went all the way to the US Supreme Court - in 1978 the right of the government to regulate "indecent" material on the airwaves was finally upheld, but only by one vote.

The "seven words" routine made Carlin's name, and encapsulated his child-like gusto for poking fun at ludicrous rules, and his sense that comedy was a form of vulgar art best placed to unpick authoritarian double-speak. Naturally he turned his scorn on religion: in one of his HBO specials he introduced the "New Commandments", a "pocket-sized" version of the original ten, one of which was "Thou shalt keep thy religion to thyself." But unlike that other great religion-baiting comic Bill Hicks, Carlin denied he was a preacher or on a mission of any kind. His was the distain of a detached observer: "I sort of gave up on the human race and the American dream and culture and nation and decided that I didn't care about the outcome," he once said, "so I could watch the whole thing with a sort of wonder and pity."

Some stand-ups talk about a difference between a comedian and a comic. Comedians - think Bob Hope or Jimmy Carr - are slick and effective deliverers of lines, crowd-pleasers who reveal nothing of themselves. Comics dare to bare their beliefs to the mob. When a comic leaves the stage, whether you liked them or not, you have learned something of them.

In Carlin's final interview, conducted, bizarrely, by Psychology Today, he spoke of seeing an illustration in Arthur Koestler's book The Act of Creation - "The jester makes jokes, he ridicules. But if his ridicule is based on sound ideas and thinking, then he can proceed to the second stage; he becomes a philosopher. And if he does these things with dazzling language then he becomes a poet too."

Carlin was bolder than most poets though, because he wasn't scared of prosaically destroying the cultural beliefs of humanity and then throwing in a few fart gags. You don't get that from Andrew Motion.

For one more essential Carlin clip, watch his classic "Religion is bullshit" routine