Frederick Douglass wanted to people to realize that knowledge is power.  He consistantly weaved his writing around to make this point: slavery is a result of ignorance, and with knowledge, slavery could be eliminated.

Douglass pointed out in his narrative that white slave owners kept slaves ignorant, because as long as they didn't know anything, they couldn't know anything. In other words, without knowledge, they would not know of the outside world, of freed slaves, of free black men, of ways to escape, of rights and responsibilities.

Many white people lived in ignorance as well, Frederick Douglass noted. They believed that slavery was simply the way of life; black people were dumb and slow and there was nothing better for them than being a slave.  So Frederick Douglass wanted black people to realzie that, if they became knowledgable and educated, they would prove to white people that this wasn't simply 'the way it was.'

I suggest you focus your thesis around Douglass' cry for knowledge as power among black people.