When Dr. McCarthy launched his career, in the years after World War II, there was great interest in exploring connections between the fields of computer science (which had been vital to military code-breaking), cognitive science (how the brain works) and mathematics.
He described attending a 1948 symposium bringing together some of the leading minds in all three subjects — including mathematicians Alan Turing and Claude Shannon and psychologist Karl Lashley — as a watershed moment in his life. It occurred to the young Dr. McCarthy, a Caltech graduate then working on his doctorate in mathematics from Princeton, that machines could be made to think like humans.
This blossomed into his infatuation with artificial intelligence, commonly known as AI. In addition to his rigorous professional pursuits in AI, Dr. McCarthy was credited with many contributions to the computing field. They included the invention in the late 1950s of list processing language, a computer programming language known as LISP that continues to be used in AI.
He also was reputed to have conceived the idea of computer time-sharing, which has been described as a contribution to the development of the Internet, and a precursor of cloud computing. Cloud computing is a method of storing data — which used to reside on a hard drive or in house servers — on a remote server accessible from the Internet or other networks.
Dr. McCarthy was not the first to work in the field now known as artificial intelligence, but many people have credited him with creating the name for it in connection with a landmark 1956 AI conference at Dartmouth College in New Hampshire, where he was then teaching mathematics.
In the late 1950s, he and Marvin Minsky, a friend and fellow AI specialist, helped start the AI lab at the Massachusetts Institute of Technology. Their views of the discipline began to diverge and, in 1962, Dr. McCarthy returned to Stanford, where he had briefly taught. He soon founded Stanford’s artificial intelligence laboratory, known as SAIL.
By that time, he became associated with the development of computers that could play chess. But when gamesmanship and showmanship appeared to be supplanting science, he turned away.
In a 2007 article, Dr. McCarthy described artificial intelligence as “the science and engineering of making intelligent machines” and said intelligence was “the computational part of the ability to achieve goals in the world.”
But in creating intelligence, he said, AI research had been only partly successful. It was not, he wrote, for lack of computing power.
“My own opinion is that the computers of 30 years ago were fast enough,” he wrote, “if only we knew how to program them.”
John McCarthy was born in Boston on Sept. 4, 1927. His father was an Irish immigrant; his mother was a Jewish immigrant from Lithuania. The family ended up during the Depression in Los Angeles, where his father was an organizer for a garment workers union.
Self-taught in mathematics as a teenager, he received an undergraduate degree in that field from the California Institute of Technology in 1948 and a PhD three years later from Princeton.
He received several major honors, including the Association for Computing Machinery’s prestigious A.M. Turing Award in 1971, the Kyoto Prize in 1988 and the National Medal of Science in 1990.
The National Medal of Science cited his “fundamental contribution to computer science and artificial intelligence, including the development of the LISP programming language.” It also noted his role in the “the concept and development of time-sharing” and “the naming and thus definition of the field of artificial intelligence itself.”
His first marriage, to Martha White, ended in divorce. His second wife, Vera Watson, a member of the American Women’s Himalayan Expedition, died in 1978 in a mountain-climbing accident while attempting to scale Annapurna in Nepal.
Survivors include his third wife, Carolyn Talcott of Stanford; two daughters from his first marriage, Susan McCarthy of San Francisco and Sarah McCarthy of Nevada City, Calif.; a son from his third marriage, Timothy McCarthy of Stanford; a brother; and two grandchildren.
Dr. McCarthy demonstrated a rigor in professional pursuits that was counterbalanced in his personal life by what a Stanford release called self-mocking humor and a philosophy of “radical optimism.”
As quoted by Stanford, Susan McCarthy described her father as holding the view that “everything will be okay even if people don’t take my advice.”