When her best friend died, she used artificial intelligence to keep talking to him

When the engineers had at last finished their work, Eugenia Kuyda opened a console on her laptop and began to type. "This is your digital monument." It had been three months since Roman Mazurenko, Kuyda's closest friend, had died. Kuyda had spent that time gathering up his old text messages, setting aside the ones that felt too personal, and feeding the rest into a neural network built by developers at her artificial intelligence startup. She had struggled with whether she was doing the right thing by bringing him back this way. At times it had even given her nightmares. But ever since Mazurenko's death, Kuyda had wanted one more chance to speak with him. A message blinked onto the screen. "You have one of the most interesting puzzles in the world in your hands," it said. Born in Belarus in 1981, Roman Mazurenko was the only child of Sergei, an engineer, and Victoria, a landscape architect. They remember him as an unusually serious child; when he was 8 he wrote a letter to his descendents declaring his most cherished values: wisdom and justice. In family photos, Mazurenko roller-skates, sails a boat, and climbs trees. Average in height, with a mop of chestnut hair, he is almost always smiling.