" I was stringing beads of different sizes in symmetrical groups—two large beads, three small ones, and so on. I had made many mistakes, and Miss Sullivan had pointed them out again and again with gentle patience. Finally I noticed a very obvious error in the sequence and for an instant I concentrated my attention on the lesson and tried to think how I should have arranged the beads. Miss Sullivan touched my forehead and spelled with decided emphasis, “Think.” In a flash I knew that the word was the name of the process that was going on in my head. This was my first conscious perception of an abstract idea. For "

― Helen Keller , The Story of My Life