Charlie Munger, the longtime business partner of Warren Buffett and one of the most consistently successful investors and thinkers of the past century, has a theory about intelligence that diverges sharply from conventional understanding. Munger does not believe that raw intellectual horsepower, the ability to process information quickly, hold large amounts of data in working memory, or generate novel solutions on demand, is the primary determinant of good judgment. He believes the primary determinant is the quality and breadth of the mental models a person has internalized. A person with a rich latticework of mental models drawn from multiple disciplines...