Let's review the use of irony before diving into chapter 15. Irony in literature concerns situations in which there is a contrast or difference between what is expected and reality or literal meanings. In the form of irony known as dramatic irony, readers are aware of something in the story of which the characters are ignorant.

In chapter 15 of The Adventures of Tom Sawyer by Mark Twain, Tom makes a difficult journey back to his home in St. Petersburg so he can leave a note for his Aunt Polly letting her know he is safe. However, when he sneaks into the house and hides under the bed, he overhears Aunt Polly, Mrs. Harper, and Sid talking about him. The irony in the situation is that readers know that Tom is there listening in to the conversation, but the women and Sid are not aware of this. The women think that Tom and his friend Joe, Mrs. Harper's son, have died. If they knew that Tom was listening in, they never would have spoken about the boys the way they do. However, because they think the boys are dead, they praise them. Aunt Polly says that Tom "was the best-hearted boy that ever was" and "such a comfort to me," whereas when Tom was around she would continually scold him. This causes Tom to begin "to have a nobler opinion of himself than ever before."