More than three centuries ago, Pascal said, "Man considering himself is the great prodigy of nature. For he cannot conceive what his body is, even less what his spirit is, and least of all how body can be united with spirit."
The French mathematician and philosopher lived at the dawn of the scientific era, but his words still ring true. We have sent spacecraft to the planets. We have listened to signals from the dawn of time. We have unraveled the mystery of starlight. We can even conceive what the body is. But the deeper human mystery remains: What is the spirit, and how is it united with body?
There is a sense among neuroscientists, psychologists and artificial intelligence researchers that the ancient riddle is ripe for solution. Powerful new imaging technologies make it possible to probe the living brain -- watch the orchestra play even as we listen to the music of thought. More powerful generations of computers provide analytical tools to model the astonishing complexity of neural circuits. Subtle refinements of molecular biology and chemistry let us fiddle with the machinery of the soul. Almost every week in Science or Nature we read of further research binding the soul inextricably to the body.
Perhaps no scientific discovery has been more fundamental than this: There is no ghost in the machine. The ghost and the machine are one and ever shall be. Some people react to this knowledge with despair or disbelief. I count it glory. "Man considering himself is the great prodigy of nature."