In today’s New York Times, I profile the neuroscientist Giulio Tononi, who has been obsessed since childhood with building a theory of consciousness–a theory that could let him measure the level of consciousness with a number, just as doctors measure temperature and blood pressure with numbers.

There’s one fascinating aspect of Tononi’s work that I simply didn’t have room for in a newspaper article (even with my editor’s long-suffering generosity with the column inches). During each moment of consciousness, Tononi argues, our brain enters a specific state. That state is an imaginably complex pattern of activity in our neurons that allows us to have a conscious experience of a swim in the ocean or a tedious tax form or sitting