If the word ignorance means lacking knowledge, there is plenty of ignorance to be found in the town of Maycomb in To Kill a Mockingbird, by Harper Lee. The characters who clearly display ignorance are a sharp contrast to those who are not ignorant, and this contrast becomes a theme which demonstrates fairness and justice in the novel.
Miss Caroline is a school teacher who tries to implement all her fancy educational training for the benefit of her students; however, she is ignorant about the way things are done in Maycomb which causes all kinds of problems for her and for the class. The fact that Scout can already read is a challenge for Miss Caroline, so in her ignorance she demands that Scout discontinue her reading; in contrast, the more informed and reasonable Atticus allows Scout to continue the practice for Scout's benefit.
Miss Stephanie Crawford is one of the town gossips who, in her ignorance, continues to spread ridiculous stories and rumours about Boo Radley; Miss Maudie, on the other hand, is a wise woman who calls Miss Stephanie's stories nonsense and does her best to make Scout, Jem, and Charles understand the truth about the Radleys. She says she remembers "Arthur Radley when he was a boy. He always spoke nicely to me, no matter what folks said he did. Spoke as nicely as he knew how.” This gives Scout new information to ponder about the mysterious Boo Radley.
Mayella Ewell is ignorant about some things, which is why she so quickly accuses Tom Robinson of raping her. In her desperation to please her angry father, she makes this claim without, it seems, a complete understanding of the consequences. Her ignorance (lack of knowledge) on the witness stand actually works in Tom's favor to some degree, but it is not something she plans or does willingly. On the other hand, the black audience in the courtroom cannot even read but understands the consequences of her testimony and have hope for their friend Tom and believe justice might prevail.
The list of such contrasting characters is long and varied, and it is the ignorant (unknowing), foolish characters who generally enhance the believability and reasonableness of the more enlightened and fair-minded characters.