One of the repeated rhetorical strategies Douglass employs is the Enlightenment "buzz words" of light and dark.
Enlightment thinkers valued reason above all else. Reason brought "light" to dark prejudices, myths, and superstitions. Slaveholders rejected reason even when presented with overwhelming "light" of the human dignity and human rights. For example, he accuses Garrison of trying to "banish all light and knowledge" and Douglass often says that "slaveholders have a hatred of the light."
Futhermore, when Douglass speaks of his mother's personal darkness, he says that she was "kept in the dark both literally and figuratively as a child." He continues, "I do not recollect ever seeing my mother by the light of day. She was with me in the night."
Douglass also rhetorcially employs biblical language and imagery to show how the "fruit" of knowledge is denied to black people. Describing his plantation, he writes, "the garden...abounded in fruits of almost every description, from the hardy apple of the north" (*the "north" itself represents freedom and knowledge). Another passage notes that the plantation's "excellent fruit was quite a temptstion to the hungry swarm of boys, as well as the older slaves." The desire for knowledge, Douglass argues, is lifelong.