Walter Scheidel, a historian and professor of history at Stanford University, is known for his work on social and economic history, particularly on the topic of wealth inequality and its historical trends. In his book titled “The Great Leveler: Violence and the History of Inequality from the Stone Age to the Twenty-First Century,” Scheidel presents a theory that the reduction of inequality throughout history has been primarily achieved through violent and disruptive events. He refers to these leveling forces as the “Four Horsemen of Leveling.”