Few things scare us more than inner emptiness. The presumed emptiness of coma or dementia scares us so much that we even sign living wills to avoid these states. Yet, as Zen masters have long known, inner emptiness can also be productive and useful. We can reach this state through meditation, concentration, music, or even during sex. In fact, our brain loves emptiness--it makes us happy. Leading brain researcher Niels Birbaumer investigates the...