Why does Frederick Douglass describe literacy as being so important in his Narrative?

In
chapter VI of his Narrative of the Life of , An American Slave, Douglass
describes the experience of being taken into the home, at the age of seven or eight, of Mr. and
Mrs. Auld. Mrs. Sophia Auld, the young Frederick discovers, is initially very kind, having never
owned slaves before and is unaccustomed to treating other human beings harshly solely because of
the color of their skin. When Frederick is first taken into the Auld home, then, he is treated
far more kindly than by previous owners and by whites in general. Mrs. Aulds humanity manifested
itself, among other ways, in believing that the young slave in her charge should be as capable
of reading as other children. Very early in the learning process, however, Mr. Auld discovered
that his wife was teaching a slave how to read and put an immediate end to Fredericks education.
Mr. Aulds rationale for prohibiting slaves from learning to read was explained by Douglass in
this chapter of his narrative:

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