To the extent that consciousness is useful, it is useful in small quantities, and for very particular kinds of tasks. It's easy to understand why you would not want to be consciously aware of the intricacies of your muscle movement, but this can be less intuitive when applied to your perceptions, thoughts, and beliefs, which are also final products of the activity of billions of nerve cells.
David has been named a John Simon Guggenheim Fellow. He will use the fellowship opportunity to pursue the genetics and neuroimaging of synesthesia.
Read a profile of David in The New Yorker: The Possibilian: What a brush with death taught David Eagleman about the mysteries of time and the brain by Burkhard Bilger.
Listen to David discussing Sum -- and actor Jeffrey Tambor reading stories from the book -- on WNYC's Radiolab.