Back in the 1600s, when neurology was born, it wasn't scientists who were looking at brains. The word scientist didn't exist. Instead, those visionary folks would have called themselves natural philosophers. As I researched this chapter of scientific history for my book Soul Made Flesh, I was struck by the way philosophers--and philosophical questions--are now making their way back into the scientific study of the brain. Last year in Discover I wrote about the work of the philosopher/neuroscientist Joshua Greene, who studies how we make moral judgments. But it turns out that neuroscientists are tackling an even deeper philosophical question: what is the self? They may not have the whole answer, but they've found some very interesting pieces of it. I've written an article on the neurobiology of the self, which appears in the November issue of Scientific American.