The tone of Douglass's narrative is sincere and instructive. A good example of this tone is in Chapter 7, when Douglass describes the poor white boys he bribed for reading lessons once Sophia Auld stopped teaching him:
This bread I used to bestow upon the hungry little urchins, who, in return, would give me that more valuable bread of knowledge. I am strongly tempted to give the names of two or three of those little boys, as a testimonial of the gratitude and affection I bear them; but prudence forbids; — not that it would injure me, but it might embarrass them; for it is almost an unpardonable offence to teach slaves to read in this Christian country.
The "bread of knowledge" is the basic reading knowledge that allows Douglass to begin educating himself so that he might one day become free. He strongly believes this is the best pathway out of enslavement. In this passage, Douglass starts by recounting a memory. He then explicitly withholds some of the information (the boys' names). Eager to demonstrate that he is being as forthright as it is possible to be, and telling the reader everything within his ethical power to tell, he describes exactly why he has withheld this detail.
His explanation is itself instructive. His readers—whom he thinks of mostly as white northerners who are sympathetic but who do not know much about the institution of slavery—don't know that these white children would face dire consequences for teaching him to read. Explaining this allows Douglass to show readers that the institution of slavery is not only trying to keep people like him from becoming educated to write a narrative such as this, but that it is also directly hurting white people as well. Douglass rarely sounds didactic, as though he is giving a lecture. Rather, he slips in the information he wants to convey to white readers as context for the stories he is trying to tell.
The patient, honest, educational tone of the narrative is significant because this narrative was one of the first widely-available descriptions of enslavement that was available for white Northerners to read. Douglass is careful to position himself as an authority and also not to alienate white readers he hopes to win over to abolitionism. Given what he describes, he would be warranted in taking a much angrier tone with readers who have been complacent about the institution of slavery. Instead, he carefully and expertly manages his tone so that his honesty never pushes away possible allies.