Which quotation best expresses Douglass's purpose for writing this passage?

The best explanation for Douglass' purpose in writing his Narrative of the Life of Frederick Douglass is to show the ways in which slavery degraded slaves and to also show the manners in which the institution of slavery degraded the slave masters as well.

The book, Narrative of the life of Frederick Douglass is a memoir which was written in 1845 and its central theme is abolition of slavery.