Artificial intelligence has been obsessed with several questions from the start: Can we build a mind out of software? If not, why not? If so, what kind of mind are we talking about? A conscious mind? Or an unconscious intelligence that seems to think but experiences nothing and has no inner mental life? These questions are central to our view of computers and how far they can go, of computation and its ultimate meaning--and of the mind and how it works.

They are deep questions with practical implications. AI researchers have long maintained that the mind provides good guidance as we approach subtle, tricky, or deep computing problems. Software today can cope with only a smattering of the information-processing problems that our minds handle routinely--when we recognize faces or pick elements out of large groups based on visual cues, use common sense, understand the nuances of natural language, or recognize what makes a musical cadence final or a joke funny or one movie better than another. AI offers to figure out how thought works and to make that knowledge available to software designers.