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As demonstrated in class last Thursday, there is a blind spot in our retina. We found it by using the cross and the dot on a sheet of paper. But when we could no longer see the dot we did not see a hole or blank spot, instead we saw white. Immediately I thought about whether or not this qualified as a hallucination. I know I saw something that wasn't there. This must mean I am always seeing something that isn't there. Standing outside a building I might see a wall where there is really a window only because the window is in my blind spot and is surrounded by the brick wall, which I can see. As far as I know I have never hallucinated to any extent larger than my blind spot(s). But if the human brain is capable of generating and perceiving mental images without receiving input then I have to start questioning reality in terms of what I am seeing. Can I really trust my brain to give me an accurate image of what is in front of me?