About the Front Cover
   The front cover illustrates the image detected by your right eye as you stand a few feet from the Mona Lisa. The gray filaments are regions where you are totally blind, a result of blood vessels in the retina blocking the detection of light.  Likewise, the large rectangular region is where the optic nerve connects with the retina, where humans are also sightless.  This is called the blind spot, and is really quite large, about the size of an apple at armís length.  As long as your eye remains fixed on the center of the painting, these gray regions are totally blocked from your gaze; you perceive nothing about the image in these areas. 
  When you first looked at the cover, you probably wondered what the gray spider-like pattern represented.  It probably struck you as quite odd, like something out of a bad science fiction movie.  It was totally unfamiliar and foreign to your conscious experience.  But how could this possibly be?  This pattern has been superimposed on your visual field since you first opened your eyes as an infant.  Even as you read this paragraph the pattern is present.  It should be more familiar to you than anything you have ever seen.  How is it possible that our conscious experience knows nothing of these blind areas? 

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