It’s difficult to agree on one definition of consciousness, so it’s confusing to read reports that someone who was in a coma for 15 years suddenly regained it. What does it mean to be aware of yourself and the world around you? If you pass out and then “regain consciousness,” it’s clear that you woke up with many of the same abilities you had when you shut your eyes. But that’s not what happened to this patient. What did he regain?