Encounters with the Archgenius.

The topic, once a staple of science fiction, has become one of the defining facts of high tech. From Apple to Amazon, Facebook to Intel, Sergey Brin to Elon Musk, the titans of the 21st century are investing fortunes and countless hours in artificial intelligence (AI). Google’s 2014 purchase of the British firm Deep Mind for something more than $400 million produced a bonanza of publicity earlier this year, when its game-playing program whipped a human master of the ancient strategy game Go. IBM is pouring $1 billion into building a business around Watson, the company’s digital Jeopardy! champion that chats with Bob Dylan in its latest ad campaign. Amazon’s new personal digital assistant, Alexa, dwells in the cloud and, like her cousins Siri (Apple), Cortana (Microsoft) and Google Now, will dispense instructions from speakers, smartphones, televisions and cars. It’s remarkable how quickly we’ve adjusted to their presence.