What does the title of the story "The Possibility of Evil" mean?

The title of the story refers primarily to Miss Strangeworth's obsession with the morality of the people in her town. She believes it is her responsibility to watch for evil behavior in everybody else, and she sees this possibility everywhere she goes. But it is only a possibility not a reality, at least in most cases. It is true that there may be some real wickedness going on in a small town and that if she suspects everybody of evil doings she will occasionally be right.

There is an old French saying which is especially pertinent to this story. It is:

Honi soit qui mal y pense

There are numerous possible interpretation of this phrase. In Miss Strangeworth it can be interpreted to mean that people who think others are evil are often evil themselves. It can also imply that people who think evil of others will end up suffering from the evil in others. Miss Strangeworth is projecting her own evil upon other people. She sees it everywhere because it is coming from inside herself.

Miss Strangeworth never concerned herself with facts; her letters all dealt with the more negotiable stuff of suspicion.

It is easy for her to see the "possibility" of evil everywhere she goes. For instance, she visits the grocery store nearly every day. She sees that the owners grandson is handling some of the cash and thinks how easy it would be for him to be "lifting petty cash from the store register." That is what she warns Mr. Lewis about in one of her anonymous letter and tarnishes the relationship between grandfather and grandson.

She finally brings out the evil in Don Crane's nature--and brings it upon herself--what he accidentally discovers that she is the author of a poison pen letter addressed to him and realizes she was the author of several she had sent to his wife. The letters all suggest that their baby daughter might be mentally retarded. In retaliation, Don Crane destroys her precious rose bushes with hedge clippers and sends her a letter reading:

LOOK OUR AT WHAT USED TO BE YOUR ROSES

So the title is a double entendre. Miss Strangeworth's concern about the possibility of evil in others has an evil motivation and brings out evil in others. This sweet little old lady is crazy and a menace to others. She will eventually be exposed, and then the whole town will turn against her. Instead of being the town's leading citizen she will be the town pariah.

Honi soit qui mal y pense

There is a passage in the Sermon on the Mount in the New Testament which is particularly appropriate to Shirley Jackson's story.

Judge not, that ye be not judged.

For with what judgment ye judge, ye shall be judged: and with what measure ye mete, it shall be measured to you again.

And why beholdest thou the mote that is in thy brother's eye, but considerest not the beam that is in thine own eye?

Or how wilt thou say to thy brother, Let me pull out the mote out of thine eye; and, behold, a beam is in thine own eye?

Thou hypocrite, first cast out the beam out of thine own eye; and then shalt thou see clearly to cast out the mote out of thy brother's eye.
                                                                    Matthew 7