“Economics is a study of mankind in the ordinary business of life.” So starts Alfred Marshall’s “Principles of Economics”, a 19th-century textbook that helped create the common language economists still use today. Marshall’s contention that economics studies the “ordinary” was not a dig, but a statement of intent. The discipline was to take seriously some of the most urgent questions in human life. How do I pay my bills? What do I do for a living? What happens if I get sick? Will I ever be able to retire?