Gauges in the head, Szpindel had called them. But there were other things in there, too. There was a model of the world, and we didn’t look outward at all; our conscious selves saw only the simulation in our heads, an interpretation of reality, endlessly refreshed by input from the senses. What happens when those senses go dark, but the model—thrown off-kilter by some trauma or tumor—-fails to refresh? How long do we stare in at that obsolete rendering, recycling and massaging the same old data in a desperate, subconscious act of utterly honest denial? How long before it dawns on us that the world we see no longer reflects the world we inhabit, that we are blind?
Months sometimes, according to the case files. For one poor woman, a year and more.
Appeals to logic fail utterly. How could you see the bird when there is no window? How do you decide where your seen half-world ends if you can’t see the other half to weigh it against? If you are dead, how can you smell your own corruption? If you do not exist, Amanda, what is talking to us now?
Useless. When you’re in the grip of Cotard’s syndrome or hemineglect you cannot be swayed by argument. When you’re in thrall to some alien artifact you know that the self is gone, that reality ends at the midline. You know it with the same unshakeable certainty of any man regarding the location of his own limbs, with that hardwired awareness that needs no other confirmation. Against that conviction, what is reason? What is logic?
— Peter Watts, Blindsight.