Given a particular input, one can often predict how a person will respond. That is not the case for the most intelligent machines in our midst. The creators of AlphaGo — a computer program built by Google’s DeepMind that decisively beat the world’s finest human player of the board game Go — admitted they could not have divined its winning moves. This unpredictability, also seen in the Facebook chatbots that were shut down after developing their own language, has stirred disquiet in the field of artificial intelligence.