For many of us, artificial intelligence (AI) started out as something to play with. We asked it to write poems and arrange our calendars; we shared its more entertaining mistakes. Then it became something to believe in: an escape from drudgery, an assistant to every profession, even perhaps the start of a new industrial revolution. Now it is something to fear. The progression has been astonishing. Governments are scrambling to draw up AI strategies, companies are reorganising operations and...