Send us Fan Mail Neuralink, Elon Musk’s neurotechnology startup, recently live-streamed footage of a paralyzed man with a brain implant playing video chess using only his mind. According to Musk, that’s just one of many medical applications for brain-computer interfaces (BCIs). But it is BCI’s non-medical applications that are generating controversy among ethicists, in the way they aspire to create a symbiosis between people and AI meant to keep humanity from falling too far behin...