How was this possible 

I have a question which the article does not cover. How does someone whos is blind and deaf learn to read and write in several languages and accomplish all the things she did. Think about it, you cannot see or hear anything and were not able to since you were a baby, how could she possibly understand anything about the world at all. The text just states that her teachers taught her what things were and the daughter of the cook used sign language to speak to her. How is this possible? How could someone use sign language when Keller could not see the sign in the first place. How would she know what human beings are, let alone complex things like nation-states or socialism. It just does not seem possible, the article only states that someone taught her things, but how. I am not buying it.