It is up to us to decide what human means, and exactly how it is different from machine, and what tasks ought and ought not to be trusted to either species of symbol-processing system. But some decisions must be made soon, while the technology is still young. And the deciding must be shared by as many citizens as possible, not just the experts. In that sense, the most important factor in whether we will all see the dawn of a humane, sustainable world in the twenty-first century will be how we deal with these machines a few of us thought up and a lot of us will be using.