In the 19th century, ice vendors used to ship blocks of ice from frozen rivers to more southerly cities. When refrigeration was invented, ice barons disparaged the ice they made as “artificial ice,” fake, not the real thing. But it didn’t work: Artificial ice was seen as cleaner, less impure, safer. When it also became cheaper to produce, it replaced the “natural” stuff rapidly. “To our 19th-century ancestors,” writes Postrel, “‘nature’ was a source of peril rather than purity.”