The Made Up World of Money Money might just be “the most powerful metaphor" we have. Matt Cardy/Getty Images Share Money is “a social agreement,” according to Frederick Kaufman, a journalism professor at the City University of New York. You and the cashier both agree that a $20 bill — a green piece of paper that any baby or dog wouldn’t hesitate to tear to shreds — is worth something, and this consensus imbues the bill with value. Eventually, babies get on board, as they’re taught the value humans have long ascribed to different types of currency; a value that’s socially constructed, but so deeply ingrained in our society that it feels silly to question.