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In 1992, a forty-six-year-old woman whom I’ll call Hannah underwent a neurological examination at a hospital in Vienna, Austria. The neurologist, Georg Goldenberg, began by asking Hannah to describe his own face. It was an odd question, but Hannah complied. The doctor had short hair and was clean shaven, she said; he wasn’t wearing glasses, and he looked like he had a bit of a tan. Goldenberg next asked Hannah about an object in front of her. It was a notebook, she answered, like the kind schoolchildren use, with a brown cover and some writing in Latin script that she couldn’t quite make out. And where exactly was the book located, the doctor asked her. He was holding it up in his left hand, Hannah replied, at just about eye level. The trouble was this: Goldenberg’s face was concealed behind a screen, the object in front of his patient was a comb, and before asking about its location, he’d hidden it beneath the table in front of him. Hannah was blind. One month earlier, she had suffered a stroke that destroyed virtually her entire visual cortex and left her all but unable to move, owing to loss of muscle coordination and chronic, epilepsy-like contractions, especially on the left side of her body. All that was bad enough. But Hannah was also left with a rarer and stranger problem: she didn’t know that she was blind.
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