Charles J. Fillmore, a revered UC Berkeley linguist whose work on how minds organize ideas has influenced American thinking from political debate to computer programming, died at his home Feb. 13 in San Francisco. He was 84.

"The world has lost a scholar of the greatest significance," George Lakoff, also a well-known linguist at Cal, wrote in a remembrance of Mr. Fillmore, whom he called "one of the world's greatest linguists - ever."

Years ago, Lakoff recalled, Mr. Fillmore told him about the case of a doctor in Boston who was on trial for murder after performing an abortion.

In court, the prosecutor referred to the "baby." The defense attorney used the word "fetus."

Each side used language to evoke different images in the minds of the jury: the word "baby" suggesting a person had been killed, and "fetus" suggesting a medical procedure. The jury found the latter idea more persuasive.

This was an example of what Mr. Fillmore called frame semantics, a field he founded in the mid-1970s. His hypothesis, Lakoff said, was that all words are "mentally defined by elements of such mental structures," or frames.

"Competing frames are used everywhere in political and social issues, and who wins depends on which frame dominates," said Lakoff, whose work in linguistics was strongly influenced by Mr. Fillmore.

Framing also helped lay the groundwork for KL-One, a knowledge representation system programmers use to allow computers to perform complex tasks, such as diagnosing diseases, and to automate reasoning.

"Chuck Fillmore was one of the world's foremost linguists," said his friend and Cal colleague Paul Kay, now a consulting linguistics professor at Stanford. "His career spanned more than half a century, during which he contributed a constant stream of original and influential ideas."

Yet Mr. Fillmore considered himself a mere OWL - linguist lingo for "ordinary working linguist."

Born on Aug. 9, 1929, Mr. Fillmore grew up in St. Paul, Minn.

"He was known for his Minnesotan modesty, gentlemanliness, and a sly wit befitting Lake Wobegon," Lakoff wrote.

Mr. Fillmore served in the Army Security Agency, intercepting Russian communications, during the early 1950s. He earned his doctorate in linguistics from the University of Michigan in 1962 before joining the faculty of Ohio State, where he remained throughout the 1960s.

He spent a year at Stanford University's Center for Advanced Study in the Behavioral Sciences and, in 1971, signed on at UC Berkeley.

He was elected to the American Academy of Arts & Sciences in 1984 and became president of the Linguistics Society of America in 1991.

Soon after retiring in 1994, Mr. Fillmore began a research project called FrameNet at UC Berkeley's International Computer Science Institute. He ran FrameNet for 18 years.

In 2012, Mr. Fillmore was diagnosed with glioblastoma, a form of brain cancer. He is survived by his wife of 42 years, Lily Wong Fillmore of San Francisco; stepchildren Angela Chinn Woodbury of Austin, Texas, Fran Chinn of San Francisco and Paul Chinn of Berkeley; and granddaughters Zoe Woodbury and Camille Woodbury, both of New York.

A public memorial is tentatively planned for May.
