Things used to be so simple. In the old days, a thousand generations ago or so, human technology wasn’t much more complicated than the twigs stripped of leaves that some chimpanzees use to fish in anthills. A large bone for a club, a pointed stick for digging, a sharp rock to scrape animal skins—such were mankind’s only tools for most of its history. Even after the appearance of more sophisticated, multipiece devices—the bow and arrow, the potter’s wheel, the ox-drawn cart—nothing was difficult to understand or decipher. The logic of a tool was clear upon inspection, or perhaps after a little experimentation. No longer. No single person can comprehend the entire workings of, say, a Boeing 747. Not its pilot, not its maintenance chief, not any of the thousands of engineers who worked upon its design. The aircraft contains six million individual parts assembled into hundreds of components and systems, each with a role to play in getting the 165-ton behemoth from Singapore to San Francisco or Sidney to Saskatoon. There are structural components such as the wings and the six sections that are joined together to form the fuselage. There are the four 21,000-horsepower Pratt & Whitney engines. The landing gear. The radar and navigation systems. The instrumentation and controls. The maintenance computers. The fire-fighting system. The emergency oxygen in case the cabin loses pressure. Understanding how and why just one subassembly works demands years of study, and even so, the comprehension never seems as palpable, as tangible, as real as the feel for flight one gets by building a few hundred paper airplanes and launching them across the schoolyard. Such complexity makes modern technology fundamentally different from anything that has gone before. Large, complex systems such as commercial airliners and nuclear power plants require large, complex organizations for their design, construction, and operation. This opens up the technology to a variety of social and organizational influences, such as the business factors described in chapter 3. More importantly, complex systems are not completely predictable.