By David Glenn

In 1932, when he had not yet finished high school, a 16-year-old Paul A. Samuelson wandered into a college lecture on overpopulation and scarcity. He was instantly enthralled by the language of economics. "I was born for the second time, the day I walked into the University of Chicago lecture hall," Mr. Samuelson told an interviewer in 2006.

Mr. Samuelson, who died on Sunday at the age of 94, went on to become one of the most distinguished economists of the last century. More than any other single scholar, Mr. Samuelson was responsible for creating the modern mathematical language of economics and for reconciling Keynesian macroeconomics with the classical models of the 19th century. He was awarded the Nobel memorial prize in economic sciences in 1970, the second year of the prize's existence.

"He was extremely catholic in his interests, and he worked on an enormous range of problems," said Jagdish N. Bhagwati, a professor of economics at Columbia University, in an interview on Sunday. "Paul stood as a giant on all dimensions—as a scholar, as a mentor. There was really no one like him."

Mr. Samuelson was appointed to the economics faculty at the Massachusetts Institute of Technology in 1940, only eight years after his adolescent epiphany in Chicago. He remained in the department for the rest of his life, and he played a central role in MIT's emergence as one of the world's leading economics programs.

When he was appointed at MIT, Mr. Samuelson was emerging as one of the most vocal American proponents of the work of John Maynard Keynes, whose theories upended some of the premises of classical economics. Mr. Samuelson's economics education at Chicago had been orthodox, but amid the catastrophe of the Great Depression he and his peers perceived that something had gone badly astray in the old models.

"Nineteen-thirty-two was a great time to be born as an economist," Mr. Samuelson wrote in an early-1980s essay that has been anthologized in Lives of the Laureates: Twenty-Three Nobel Economists (MIT Press). "The sleeping beauty of political economy was waiting for the enlivening hand of new methods, new paradigms, new hired hands, and new problems,"

A Mathematical Focus

But unlike his fellow Keynesian John Kenneth Galbraith, Mr. Samuelson believed that it was crucial to translate Keynes's insights—and, for that matter, virtually every economic idea—into mathematical terms. The rigors of math, he insisted, would make economics much more powerful and precise. Why waste pages of prose on an idea that could be better expressed as a theorem?

"The laborious literary working over of essentially simple mathematical concepts such as is characteristic of much of modern economic theory," Mr. Samuelson wrote in the 1940s, "is not only unrewarding from the standpoint of advancing the science, but involves as well mental gymnastics of a particularly depraved type."

There is a small irony in Mr. Samuelson's role as mathematical prophet, said Mr. Bhagwati, who studied with Mr. Samuelson in the 1950s and remained close to him until his death. Though Mr. Samuelson had brilliant mathematical intuitions, Mr. Bhagwati said, he was not especially technically strong in mathematics, and he often left it to colleagues to work out the final versions of theorems.

Mr. Bhagwati quoted an old line from Lionel W. McKenzie, a professor emeritus of economics at the University of Rochester: "Mathematical economists have spent their entire lives trying to disprove Paul Samuelson's conjectures, but they have only wound up proving them."

In 1948, Mr. Samuelson wrote an introductory textbook, known simply as Economics, which became one of the best-selling college textbooks of the 20th century. So ubiquitous was the book that when a Marxist scholar named Marc Linder published a multivolume economic treatise in the 1970s, he called it The Anti-Samuelson.

According to several written accounts, Mr. Samuelson remained loyal to MIT even as many other institutions tried to lure him away. One tale has it that when MIT's department earned a mediocre ranking in a survey of economists in the 1950s, Mr. Samuelson said, "We may not be the best department, but we certainly are the happiest."

Mr. Bhagwati came to study at MIT after graduating from the University of Cambridge in 1956, and he was astonished by the informality of the department. "You could go into Paul Samuelson's office at any time," he said. "There were no office hours. He would offer plenty of his time. I had never seen anything like that in England. Here was a guy who was literally the greatest economist of his time, and he had an open door."

In a whimsical third-person passage in his Lives of the Laureates essay, Mr. Samuelson wrote that "PAS has already been incredibly lucky throughout his lifetime, overpaid and underworked." He added that he worked furiously during his 20s because he feared he would die young, as his father and certain other relatives did.

In the event, of course, Mr. Samuelson lived an extraordinarily long life, and he remained lucid until the end. (As recently as June, he gave an interview to The Atlantic.) Mr. Bhagwati saw Mr. Samuelson three weeks ago, and said that he was still able then to talk coherently about the state of economics.

"He embodied a certain culture of giving and mentoring and building on scholarship and being fair-minded," Mr. Bhagwati said. "He was someone we all adored, and we're going to miss him."