What effect does Douglass's mix of factual and subjective description produce?

Frederick Douglass famous autobiography contain factual and subjective descriptions which change the way people think. He empowered people to stand for what is right and freedom from slavery is essential and worth fighting for. Moreover, his persuasive form of writing liberated the black men from all forms of subordination and unjust practices. After all, Douglass produce freedom from his influential work.