Shirley Jackson's view of the world was always a little off center. She had a way of presenting characters and situations that often had a hidden message about the quirky side of human nature.
In the short story entitled, "The Possibility of Evil," Jackson presents Miss Strangeworth as a woman in society who is well accepted and respected in her life and throughout the town.
When people meet Miss Strangeworth, she impresses them as being a cornerstone of the community, well-grounded and deeply rooted to all that is good and decent in this world. Because of these perceptions, we are all shocked when we learn her secret. As a society, we often judge people based upon what we see, and not what or who a person really is. As a society we are easily tricked, and often unaware that even the nicest people in the world can hide behind outward appearances.
There is a quote by Shakespeare that says, "There is nothing good or bad, but thinking makes it so." This basically means that things are bad sometimes only if they are perceived as bad. For instance, in this story, no one thinks Miss Strangeworth is evil. They cannot conceive of such a thing with Miss Strangeworth. However, she is the evil in in this story.
On the other side of the argument, things are often considered evil simply because of the perception. In a male-dominated society, a woman might be considered bad if she went to school and started to share her own ideas.
In "The Possibility of Evil," Miss Strangeworth's perception of evil is not accurate. The narrator tells us that Miss Strangeworth does not deal in facts. Someone does not need to actually be bad to be considered bad in her mind. For Miss Strangeworth, it is the "possibility" that someone might be bad, in order for her to act on this "fact" and send a letter. The evil does not actually exist, only Miss Stangeworth's perception of evil, which is not a valid observation.
Society and people like Miss Strangeworth are confused equally when a person or situation is judge by appearance rather than the truth.