That evening, after dinner, he told his wife, A strange case turned up at the surgery today, it might be a variant of psychic blindness or amaurosis, but there appears to be no evidence of any such symptoms ever having been established, What are these illnesses, amaurosis and that other thing, his wife asked him. The doctor gave an explanation within the grasp of a layman and capable of satisfying her curiosity, then he went to the bookcase where he kept his medical books, some dating back to his university years, others more recent and some just published which he still had not had time to study. He checked the indexes and methodically began reading everything he could find about agnosia and amaurosis, with the uncomfortable impression of being an intruder in a field beyond his competence, the mysterious terrain of neurosurgery, about which he only had the vaguest notion. Late that night, he laid aside the books he had been studying, rubbed his weary eyes and leaned back in his chair. At that moment the alternative presented itself as clear as could be. If it were a case of agnosia, the patient would now be seeing what he had always seen, that is to say, there would have been no diminution of his visual powers, his brain would simply have been incapable of recognising a chair wherever there happened to be a chair, in other words, he would continue to react correctly to the luminous stimuli leading to the optic nerve, but, to use simple terms within the grasp of the layman, he would have lost the capacity to know what he knew and, moreover, to express it. As for amaurosis, here there was no doubt. For this to be effectively the case, the patient would have to see everything black, if you'll excuse the use of the verb to see, when this was a case of total darkness. The blind man had categorically stated that he could see, if you'll excuse that verb again, a thick, uniform white colour as if he had plunged with open eyes into a milky sea. A white amaurosis, apart from being etymologically a contradiction, would also be a neurological impossibility, since the brain, which would be unable to perceive the images, forms and colours of reality, would likewise be incapable, in a manner of speaking, of being covered in white, a continuous white, like a white painting without tonalities, the colours, forms and images that reality itself might present to someone with normal vision, however difficult it may be to speak, with any accuracy, of normal vision. With the clear conscience of having fetched up in a dead end, the doctor shook his head despondently and looked around him. His wife had already gone off to bed, he vaguely remembered her coming up to him for a moment and kissing him on the head, I'm off to bed, she must have told him, the flat was now silent, books scattered on the table, What's this, he thought to himself, and suddenly he felt afraid, as if he himself were about to turn blind any minute now and he already knew it. He held his breath and waited. Nothing happened. It happened a minute later as he was gathering up the books to return them to the bookshelf. First he perceived that he could no longer see his hands, then he knew he was blind.