Comedian George Carlin once observed that "Death was caused by swallowing small amounts of saliva over a long period of time."

Who could argue with him? The comedian who made social commentary and observational humor look easy, died of heart failure on Sunday at age 71.

Tributes to Mr. Carlin's genius always mention that he was part of an influential comic fraternity that included Lenny Bruce, Dick Gregory, Mort Sahl and Richard Pryor -- comedy giants who were never comfortable with the status quo and said so on stage, TV and in comedy albums that sold in the millions.

George Carlin's most famous routine got him arrested when he performed it in Milwaukee in 1972. "Seven Words You Can Never Say on Television" was a catalogue of words that censors considered obscene and unfit for mainstream media until this day. Mr. Carlin highlighted the words to show the arbitrariness of what society considers "indecent" and "obscene" language. Behind his scatological recitation was the indignation of a comic who cared deeply about words and what they meant.

Many of his observations were based on a keen sensitivity to linguistic absurdities: "If lawyers are disbarred and clergymen defrocked, doesn't it follow that electricians can be delighted [and] musicians denoted?"

Euphemisms, politics and word play formed the core of his comedy and the secret of his appeal for half a century. Mr. Carlin was among the last of a fearless breed.

"I think it's the duty of the comedian to find out where the line is drawn and to cross it deliberately," Mr. Carlin said, summing up his comic philosophy. It was a credo he lived and died by.