What is consciousness and why do we have it?
This is an old question but we can throw some new light on it based on the realization of the last few decades that our minds, like our bodies, have evolved to fit the ecological niche that our ancestors lived in. Consciousness, like everything else, must have been an essential tool for survival. Thus, we should start not by trying to think about what it feels like to be awake or whether computers can get pissed off at Bill Gates, too, but rather about what survival value you get by being a conscious being rather than an automaton.
Roger Penrose tells a story (originally from Konrad Lorenz) in The Emperor's New Mind which is very illuminating (though he seems to have missed its significance). A chimpanzee is given a box, and a banana hung too high to reach directly. "...the matter gave him no peace, and he returned to it again. then, suddenly -- and there is no other way to describe it-- his previously gloomy face "lit up". His eyes now moved from the banana to the empty space beneath it on the ground, from this to the box, then back to the space, and from there to the banana. The next moment he gave a cry of joy, and somersaulted over to the box in sheer high spirits. completely assured of his success, he pushed the box below the banana. No man watching him could doubt the existence of a genuine "Aha" experience in anthropoid apes."
It's clearly true that this anecdote reveals that chimpanzees are conscious beings who like us get jazzed when they solve a tough problem. But it tells us much more than that, because we know exactly what happened. The chimp constructed a mental model of the situation and then manipulated the mental model until he found the solution to his problem in the virtual world. Obtaining the banana was then a mere matter of translating his mental representation into an algorithm of actions.
"But the dog did nothing in the night-time."
"Ah!" replied the ever-perspicacious Holmes, "That was the curious incident."
We tend to focus on what the chimp did, but the key observation is what the chimp did not do: he did not randomly move around and exercise all conceivable actions physically available to him to get the food. He saved a tremendous amount of energy and risk by working out the consequences of each possible action in his head before selecting a plausible course.
This point is worth serious reflection. For any fairly complex creature, which has thousands of behavior repertoires and encounters millions of circumstances through its life, the ability to sort out which one to use when without trying them all represents a literally mind-boggling opportunity to save time and energy and minimize the inevitable dangers of life. Imagine you are trapped in a fenced enclosure. If you're a creature of conditioned responses, you simply walk until you bump into the fence, randomly try another direction, and walk until you bump into the fence again: this is what a house fly does trying to escape a house. If you're a creature with a conscious mind, you look around (which is much easier than walking around) and identify an anomalous appearance in the fence: an opening? You only need to investigate one place; if you're clever you may even be able to ascertain what actions you'll take to get out and what you'll do after you escape.
What does it take to accomplish this sort of trick? Well, first of all you obviously have to have the ability to construct mental representations of the physical world: you have to have ideas corresponding to objects and their manipulations. But that's not enough: you also have to have a model of yourself to go along with the models of the world outside, because the whole point is to try to anticipate the results of various things that you could do. You have to envision yourself doing them and therefore must model your physical state and physical abilities, and your mental state and mental abilities, since these are the variables which constrain what actions you must examine. Finally, we must have a model of the passing of time and the present moment, since by definition we are manipulating our model of the world and ourselves in time as well as space: thought is useless if it provokes ill-timed action or actions rendered impossible or irrelevant because of timing. We have to have a picture of "now" against which we can reference our future scenarios, and we have to account for the time that's passing while we think. In summary, you can't be conscious in the evolutionary sense -- able to think before acting and thereby act more efficiently -- unless you're conscious in the commonplace sense of being aware of yourself: the cogito ergo sum sense of Descartes.
Thus when Stephen Pinker defines intelligence as "the use of thought to achieve goals" and then goes on to worry about what consciousness in the sense of being sentient is, he's missed the point: his definition applies not to intelligence but to consciousness. We're so used to being awake that we get confused about the distinction. You can't be intelligent without being conscious because you have to have an understanding of yourself before you can envision how that self can achieve the survival-related goals of food, sex, shelter, avoidance of danger, etc.
This approach to the subject also tells us immediately what conscious doesn't do. We all know that forming and manipulating mental models takes times. Cognitive scientists can tell you that asking a person to rotate an object in their heads takes a similar amount of time to rotating it in their hands. Conscious thought is too damned slow to be useful in situations that demand immediate action: either life-threatening or life-enhancing.
In our modern life, athletic activities play much of this role, and it is a truism that too much thinking gets in the way of athletic success. A basketball player on a streak is often said to be "unconscious"; an athlete in a slump has no conscious idea of what is different from his (her) previous behavior. Athletic skill is honed by mind-boggling repetition: in basketball, for example, one practices shots and passes from every place on the court, under every circumstance, from every bodily position, against every defense.
Athletic activites are the antithesis of consciousness: we form a huge look-up table (in computer programming vernacular) from which we can instantly access our exact action by exploiting the associative memory capabilities of a neural net. The table is not directly accessible to our conscious mind: what exactly did you do to make the shot go in? This is also why the actions can be so absurd: we explicitly do not think out the consequences. A Super Bowl quarterback can still throw idiotic interceptions; a 300+ hitter swings at a curve ball at his ankles. We are only conscious of these things after the fact, because conscious thought is too slow: it supervises and archives but does not control our actions.
Evolution has no forethought and no obligation to obey simple categorizations; conscious, semi-conscious and unconscious processes can and do take place simultaneously in any being at every moment. In our study of other species we have oscillated between bizarre Disney-esque anthopomorphization and absurd "scientific" denials that e.g. a dog has thoughts or feelings. Accepting the definition of consciousness as the ability to envision actions before one takes them gives us a rigorous test for the level of consciousness of our companion creatures on the Earth. By thinking functionally, we put off the irritating impossibility of trying to account in one swift stroke for all the ramifications that hundreds of millions of years of neurological evolution have created in our own minds, and enable ourselves to focus on the simplest cases and thus proceed with learning principles that can later be applied to our own minds. We can study the relevant aspects of simpler creatures with a basis for generalization.
I'd like to say I'm off envisioning the huge improvements in the human condition that will result from the insight disclosed in these pages, but I'll be too busy trying to figure out why I still can't make a jump shot. Any ideas?