How does the story achieve its authenticity?

At its core, the narrative uses historical facts to illustrate ma's cruelty to man. Northup reveals just how awful man can be to man. The lucrativeness of slavery and concomitant racism created a situation that the South jealously guarded. In order to keep it intact, many felt that black people must be stripped of all rights and must be frightened or manipulated into working hard and knowing their artificially subordinate place in society. Violence and abuse of all kinds began to come naturally to slaveowners, for deep down they were aware of the flimsiness of their claims that slavery was a positive force. Fear of rebellion also stoked their increasingly cruel treatment of slaves, and when violence went on for so long unchecked, it became the norm. Man's baser impulses — such as greed, selfishness, and desire for power — cannot easily be ignored or quelled in the context of slavery.