Douglass' primary claim in his narrative is that a nation predicated upon individual freedom cannot allow slavery to exist. His first hand accounts of the cruel nature of slavery and the thought processes of the various slave owners help to substantiate his assertion. It is difficult to challenge the accuracy of the first hand account offered. At the same time, Douglass' exploration of Christianity, and its hypocrisy when used to justify slavery, and the idea that the promise of freedom cannot be realized when a group of people are enslaved, helps to bolster the claims that slavery is America's "original sin."
Douglass's central claim in his autobiography is that slavery is as harmful to whites as it is to slaves. He says of Sophia Auld, "Slavery proved as injurious to her as it did to me" (page 28). His evidence for this claim is that when he first meets her in Baltimore, she is a very kind woman. He writes:
"Slavery soon proved its ability to divest her of these heavenly qualities. Under its influence, the tender heart became stone, and the lamblike disposition gave way to one of tiger‐like fierceness" (page 28).
The first step in her transition from kindness to cruelty is when she is instructed to cease teaching Frederick Douglass to read. Her husband tells her that instructing her slave in literacy will spoil him as a slave, and she stops teaching young Frederick. This is her first step from being a kind-hearted woman with generous tendencies to harnessing her natural instincts and instead becoming cruel. Frederick Douglass shows her fast transformation from generosity to hard-heartedness to show the pernicious effect slavery has on white slave owners.