In the nineteen-forties, when the Massachusetts Institute of Technology was considering adopting a new economics textbook, the school’s president received warnings about the book’s author: “It is perfectly obvious that the young man is socially-minded if not strictly communistic,” one correspondent wrote. The young man in question was the American economist Paul Samuelson, a future Nobel laureate. Samuelson’s textbook “Economics,” published in 1948, would dominate the market for nearly half a century; it introduced a Keynesian vision—in which government would take a more active role in managing the economy and promoting full employment—to generations of students and sold millions of copies.