Brain-computer interfaces may change what it means to be human. Technologies are often billed as^[1] transformative. For William Kochevar, the term is justified^[2]. Mr Kochevar is paralysed^[3] below the shoulders after a cycling accident, yet has managed to feed himself by his own hand. This remarkable feat is partly thanks to electrodes^[4], implanted in his right arm, which stimulate muscles. But the real magic lies higher up.