Drucker taught that management is "a liberal art", and he infused his management advice with interdisciplinary lessons from history, sociology, psychology, philosophy, culture and religion. He also believed strongly that all institutions, including those in the private sector, have a responsibility to the whole of society. "The fact is," Drucker wrote in his 1973 "Management: Tasks, Responsibilities, Practices", "that in modern society there is no other leadership group but managers. If the managers of our major institutions, and especially of business, do not take responsibility for the common good, no one else can or will."