What did Douglass believe his ability to read had caused? What evidence shows why he felt that way?

In Chapter VII of his Narrative, Frederick Douglass enlists the children of Baltimore to teach him how to read.  As he recounts,

The plan which I adopted, and the one by which I was most successful, was that of making friends of all the little white boys whom I met in the street.  As many of these as I could, I converted into teachers.  With their kindly aid, obtained at different times and in different places, I finally succeeded in learning to read.

As he tells us, this knowledge gives Douglass the desire for freedom through reading a book entitled "The Columbian Orator."  Through reading this book, its "dialogue between a master and his slave" and its "mighty speeches on and in behalf of Catholic emancipation," Douglass encounters both "a bold denunciation of slavery, and a powerful vindication of human rights."  After he learns how to read and encounters these arguments, he decides that he can no longer tolerate his condition as a slave:

Freedom now appeared, to disappear no more forever.  It was heard in every sound, and seen in every thing.  It was every present to torment me with a sense of my wretched condition.  I saw nothing without seeing it, I heard nothing without hearing it, and felt nothing without feeling it.  It looked from every star, it smiled in every calm, breathed in every wind, and moved in every storm.

From this quotation you see that Douglass' literacy is directly responsible for his desire for "Freedom" which leads to his eventual escape and emancipation.