had gone to the dogs since the golden age (and some still do), while socialists championed growth, technology and innovation to liberate the working class. My latest Mind and Matter column for the Wall Street Journal is on how the future turns out: Last month a crash dummy flew to 5,000 feet above ground level in a personal jet pack. The inventor, New Zealander Glenn Martin, has spent decades on the project and is ready to start selling the device for $100,000 each next year. The gasoline-driven machine can stay aloft for 30 minutes, thanks to what is, in effect, a pair of large leaf-blowers. A parachute provides partial reassurance if something should go wrong. Mr. Martin's achievement is a reminder that, though we often underestimate the progress of a technology, sometimes we overestimate it. Back in the 1950s it seemed almost obvious that by the 21st century jet packs would be ubiquitous and routine aids to travel. They featured in sci-fi novels and comics and television series like "Lost in Space." A time-traveler who arrived from that era might be impressed by our Internet and mobile phones but amazed at our lack of working jet packs. My latest Mind and Matter column at the Wall Street Journal is about the precautionary principle as exemplified by the German e coli outbreak, which has now killed 29. Less precaution about new technology might have meant fewer deaths: A technology that might have prevented contaminated produce from infecting thousands of Germans with