Writing before slaves were freed in the United States, Douglass' main objective in the Narrative is to dispel any notion that slavery is good for those enslaved. He point-by-point counters a Southern narrative that argued that slavery benefitted black people.
Pro-slavery whites pointed out that black people, when questioned, said they were happy with their situation. They also remarked that slaves were often singing, which was said to prove they were happy, asserted that slaves were well taken of with cradle-to-grave security offered by benign masters, and argued that Christianity insured that white slave owners treated slaves with compassion.
Using stories to illustrate each of his points, Douglass shows that black slaves only tell whites they are happy to avoid retribution, that they sing to mourn and lament their fate, and that owners who have gone to revival meetings and come back "converted" to Christianity feel even more emboldened to beat and mistreat their slaves, because it is Biblically sanctioned that slaves must obey their masters. As for the kind of cradle-to-grave care slaves get, Douglass graphically describes the frequent and brutal beatings his master, Mr. Auld, dealt out, and then discusses his own treatment as a child slave on the plantation. He never had a pair of shoes, no matter how cold it got ,and had only a single thin shift to wear, summer and winter. Most of the slaves were hungry because they were ill-fed, and they were expected to toil sun-up to sundown.
Douglass also describes the way it corroded his soul to not know his birth date, to be told he couldn't learn to read after the wife of his Baltimore owner started to teach him, and to realize that slavery was a condition he would never grow out of. He makes an eloquent case for slavery as an evil and indefensible institution, and he points out as well that it corrupts whites to have such immense power over other human beings.