[Why two eyes?].

Having two eyes instead of just one is advantageous in at least six respects: the danger of blindness is decreased, the visual field is enlarged, stereoscopic depth perception is possible on the basis of binocular disparities, the position of the eyes relative to the head can be computed from the images of both eyes, visual obstacles in front of the horopter perceptually shrink, and the signal-to-noise ratio is increased.