Sam Harris expands on his earlier thoughts:
The fact that the universe is illuminated where you stand—that your thoughts and moods and sensations have a qualitative character—is a mystery, exceeded only by the mystery that there should be something rather than nothing in this universe. How is it that unconscious events can give rise to consciousness? Not only do we have no idea, but it seems impossible to imagine what sort of idea could fit in the space provided. Therefore, although science may ultimately show us how to truly maximize human well-being, it may still fail to dispel the fundamental mystery of our mental life.
The Dish 