At the Heavenly Models home for deceased economists, an award is being presented to the resident whose work best explains financial crises, global warming, and other pressing issues of today. The favored candidates include John Maynard Keynes, the patron saint of stimulus programs; Hyman Minsky, an American disciple of Mr. Keynes who warned about the dangers of financial deregulation; and Milton Friedman, the late Chicago economist. (Mr. Friedman's free market principles are out of vogue, but Federal Reserve Chairman Ben Bernanke recently took his advice on how to prevent depressions by pumping money into the economy.)

The winner's name, however, turns out to be much less familiar: Arthur Cecil Pigou (pronounced "Arthur See-sil Pig-oo"). Stepping from the wings, a strapping Englishman with fair, wavy hair and a luxuriant moustache, smiles awkwardly and accepts his prize. A contemporary of Mr. Keynes at Cambridge University, Mr. Pigou was, for a long time, the forgotten man of economics. In the years leading up to his death, in 1959, he was a reclusive figure, rarely venturing from his rooms at King's College. His novel ideas on taxing polluters and making health insurance compulsory were met with indifference: Keynesianism was all the rage.

Today Mr. Pigou's intellectual legacy is being rediscovered, and, unlike those of Messrs. Keynes and Friedman, it enjoys bipartisan appeal. Leading Republican-leaning economists such as Greg Mankiw and Gary Becker have joined Democrats such as Paul Krugman and Amartya Sen in recommending a Pigovian approach to policy. Much of President Barack Obama's agenda—financial regulation, cap and trade, health care reform—is an application of Mr. Pigou's principles. Whether the president knows it or not, he is a Pigovian.

Mr. Pigou pioneered the study of market failure—the branch of economics that explores why free enterprise sometimes. During the 1930s, Mr. Keynes lampooned him as a reactionary because of his suggestion that the economic slump would eventually recover of its own accord.

But while Mr. Pigou believed capitalism works tolerably most of the time, he also demonstrated how, on occasion, it malfunctions. His key insight was that actions in one part of the economy can have unintended consequences in others.