When six-foot-four inch Marty first rolled into Stop & Shop, the robot walked into history. Social robot experts say it is among the first instance of a robot deployed in a customer environment, namely supermarkets in the Northeast. Marty rolls around the store looking for spills with its three cameras. It does take the place of the human worker, called an associate, that did the same thing, but it means the associate can do something else. Doing the walk-around of the store is seen as a mundane task.

Human beings begin to learn the difference before we learn to speak--and thankfully so. We owe much of our success as a species to our capacity for moral reasoning. It's the glue that holds human social groups together, the key to our fraught but effective ability to cooperate. We are (most believe) the lone moral agents on planet Earth--but this may not last. The day may come soon when we are forced to share this status with a new kind of being, one whose intelligence is of our own design. Robots are coming, that much is sure. They are coming to our streets as self-driving cars, to our military as automated drones, to our homes as elder-care robots--and that's just to name a few on the horizon (Ten million households already enjoy cleaner floors thanks to a relatively dumb little robot called the Roomba). What we don't know is how smart they will eventually become. Some believe human-level artificial intelligence is pure science fiction; others believe they will far surpass us in intelligence--and sooner rather than later.