The study of consciousness is difficult because (among other reasons) it is very hard to "get at": we do not have a "consciousness-o-meter" by which to read out the level of another being's consciousness. In fact, aside from being conscious ourselves, the only thing we have to go on is the behavior of others, and the inference of other consciousness that we can make from that.
This has led to all kinds of problems, including the question of whether consciousness is in any way essential: does it do anything? Is consciousness necessary to create complex behavior? One thought experiment dreamed up by the philosopher David Chalmers attempts to clarify this puzzle. It is called The Philospher's Zombie.
It goes like this:
Could you imagine a being that acted in every way like yourself or one of your friends, whom you know to be conscious -- but that being is "dark inside"? There is "nobody home". This being is the philospher's zombie.
Whatever your answer, it should help clarify your own notion of what consciousness is and does.
If you can imagine a such a zombie, then it must mean that consciousness does not actually do anything -- since a 'droid could come up with all the same behaviors as a conscious being. Consciousness is inessential. R2D2 and C3PO need not really have any feelings, fear, etc, even though R2D2 acts cute and devoted, and C3PO gets all dithery in a tight spot.
On the other hand, if you believe the zombie is impossible then you must feel that consciousness is necessary for at least some actions. Zombies might not talk about dreams, for instance, because there is no distinction between sleep and waking. There is "nothing it is like" to be a zombie, so there might be many ways in which the observable culture of a zombie world differed from our own.
Travis argues that because zombies lack free will, a zombie world would be a much more mechanistic place than our world. In other words, the zombie with behavior identical to ours, but without free will, is impossible.
Zombieworld by Travis Scrimshaw
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