The recent market turmoil is rocking investors around the globe. But it is raising the stock of one person: a little-known economist whose views have suddenly become very popular.

Hyman Minsky, who died more than a decade ago, spent much of his career advancing the idea that financial systems are inherently susceptible to bouts of speculation that, if they last long enough, end in crises. At a time when many economists were coming to believe in the efficiency of markets, Mr. Minsky was considered somewhat of a radical for...