Gillian Tett of the Financial Times reviews The Usefulness of Useless Knowledge (Princeton University Press), founding Director Abraham Flexner's influential 1939 essay newly republished with a companion essay by Robbert Dijkgraaf, Director and Leon Levy Professor. The book, Tett writes, argues “that the most powerful intellectual and technological breakthroughs usually emerged from research that initially appeared 'useless,' without much relevance to real...