Vaughan Bell draws a fascinating comparison:
[T]he idea that we see the world as it is, is a bit of a myth, because we experience things that aren’t there all the time. The eye allows light to fall on the retina, two flat areas of photoreceptor cells which provide only patchy and poor resolution coverage of the visual field, and yet we have a very rich visual experience. The brain is filling in the rest. In your blind spots, you receive no visual information and yet we don’t have two black spots in our vision because we ‘hallucinate’ the best guess visual experience. These are not usually considered hallucinations because the experience remains stable and predictable but these same processes, with just slight instabilities, can lead to spectacular hallucinatory states – such as Charles Bonnet syndrome –where damage to the retina leads to visions of monkeys, rabbits and little men. In other words, there are as many causes for hallucinations as there are causes for our perception of reality.
The Dish 