From chess to shogi, artificial intelligence has swept aside the grandmasters of humans' most challenging board games. Now the technology's impact is rapidly spreading in the broader world. A taxi company in Japan has boosted its passenger numbers by 20% by introducing an AI system that anticipates peak demand and dispatches drivers accordingly. In the U.S., AI is used in courtrooms to calculate the risk of recidivism and to set prison terms. AI is changing the world - but for better or worse?