How do you prove to a suitable level of confidence that a system as complex as a modern automobile can safely operate autonomously, in the middle of multi-lane traffic, pedestrians, bicyclists, farm vehicles, construction vehicles, bridges, cloverleafs, stop lights, toll booths, etc.? The answer is that you might not be able to prove the desired level of safety as the systems are currently envisioned. So are self-driving automobile efforts doomed before they really begin?