[T]he next time you hear serious-sounding people explaining the need for fiscal austerity, try to parse their argument. Almost surely, you'll discover that what sounds like hardheaded realism actually rests on a foundation of fantasy, on the belief that invisible vigilantes will punish us if we're bad and the confidence fairy will reward us if we're good. And real-world policy - policy that will blight the lives of millions of working families - is being built on that foundation.