In contemporary sci-fi—HBO's "Westworld," for example—sentient machines take up arms against humanity. In the real world, intelligent—and increasingly autonomous—robots are being created with weapons already in hand. More than 16 countries (not to mention terrorist groups like the Islamic State) already possess armed drones. Militaries around the globe are racing to deploy robots at sea, on the ground and in the air. For now, these machines operate mostly under human control, but that may not be the case for long. This raises a question: What happens when a Predator drone has as much autonomy as a driverless car?