What is the major theme in the Narrative of the Life of Frederick Douglass, an American Slave?

Douglass's
work has many themes, but perhaps the most important is the corrupting influence of slavery. It
is important to remember that the Narrative was very much a document of the abolitionist
movement, and Douglass is searing in his indictment of an institution that, he says, corrupts
everyone involved. It gives nearly unlimited power to evil men like Mr. Covey, and even infects
good and generous people like Sophia Auld with hate and a sense of their own superiority. It
perverts Christianity, which is put into service providing ideological justifications for it.
Perhaps worst of all is the effect it has on the slaves themselves. After working under the
brutal Mr. Covey for a year, Douglass describes himself as a shell of a man:

I was broken in body, soul, and spirit. My natural elasticity was
crushed, my intellect languished, the disposition to read departed, the cheerful spark that
lingered about my eye died; the dark night of slavery closed in upon me; and behold a man
transformed into a brute!

But Douglass's story is also a
story of strength and redemption, and he resists this terrible dehumanization first by fighting
back against Mr. Covey and then by running away to freedom.