What does Helen Keller mean in her book The Story of My Life, when she says "'Light! Give me light!' was the wordless cry of my soul?"

In her autobiography, The Story of My Life, Helen Keller is well-known for her poetic use of language to express herself. After an illness, and having been left blind and deaf at the age of nineteen months, Helen struggles for several years to make herself understood, and is constantly frustrated at her futile attempts to communicate like the rest of her family appear to do. She even puts on her father's glasses and holds the newspaper in front of her eyes because she knows her father does that, but of course her attempts do not help and only serve to increase her frustration. 

When Annie does arrive to tutor Helen, Helen recalls in chapter 4 that it is "the most important day I remember in all my life" because it changes everything. Helen is desperate to learn and to be a part of the world she knows exists but has no access to and this is why she says "'Light! give me light!' was the wordless cry of my soul..." Helen has no words, no vocabulary because she has never been able to learn to speak. Her "wordless" cry reveals her inability to make herself understood. Light is also something that eludes Helen and she recognizes that the key to everything is language and understanding, something she feels that Annie Sullivan will be able to give to her; hence, Helen adds that "the light of love shone on me in that very hour."

In the book, she makes numerous references to the "soul," recognizing that, for her, it is the link between the "darkness" which fills her head and the "light" or real learning which will be responsible for her "soul's sudden awakening" (chapter 5) after the arrival of Annie Sullivan.