The great MIT economist Paul Samuelson died today, at age 94. The NYT, in its obituary, calls him “the foremost academic economist of the 20th century,” which sounds about right. Samuelson’s Foundations of Economic Analysis, a reworking of his doctoral dissertation that was first published in 1947, transformed graduate education in economics (by ending what he called “the laborious literary working over of essentially simple mathematical concepts,” and replacing this “peculiarly depraved” practice with hardcore math). And his 1948 textbook Economics—a brilliant literary reworking of economic ideas for a less sophisticated audience—dominated undergraduate education in the subject for decades. He also had his hand in many of the great economic advances of his day, including one that I spent way too much of the past decade immersed in, the efficient market hypothesis.

Yet he isn’t nearly as well known to the rest of the world as his fellow economists Milton Friedman or John Maynard Keynes. This isn’t because Samuelson was hiding out in the ivory tower. He wrote a textbook that introduced generations of American college students to economics. He wrote a regular column for Newsweek for years (and recruited Friedman to write for the magazine too). He was always accessible to reporters and ready to spell out economic concepts in clear language.