The pervading theme throughout the entirety of the novel is undoubtedly that assumptions can be harmful and often wrong. This theme can be viewed through another lens as well: focusing on appearances, and the external, can often give rise to false assumptions and prejudices. This particular theme can be tracked through numerous instances in the book, spanning simple moments, like when Mrs. Forbes is utterly mortified by her husband’s unwillingness to get dressed up for the DiSilvio’s party. Mrs. Forbes assumes that because the DiSilvios are well-dressed and wealthy, that they are inherently good people. She wishes that Mr. Forbes will dress in a similar manner so that they, too, appear to be as successful and good as the DiSilvios. By the end of the novel it is clear that regardless of paint spattered jeans or fine pressed suits, assumptions of goodness and intention cannot be made based on appearances alone. This theme carries into the larger frameworks of the novel as well, such as in the portrayal of the Phelps family.

Just as the DiSilvios make negative assumptions about the families who are in the lower classes, so does Mrs. Forbes about the Jenkinses, and the Jenkinses about the Phelpses.