According to the narrator what is the veil's one desirable effect in The Ministers Black Veil?

The black veil is a symbol of secret sin. This could represent the secret sin that all men carry in their hearts, or it could be representative of Mr. Hooper's specific sin, adultery. Edgar Allan Poe speculated that Minister Hooper may have had an affair with the young lady who died at the beginning of the story, as this is the first day he wears the veil, "and that a crime of dark dye, (having reference to the young lady) has been committed, is a point which only minds congenial with that of the author will perceive." Also, he is unable to tell his fiancée why he wears the veil due to a vow he has made, and is unwilling to show his face to the young lady even in death. Also, two funeral attendees see a vision of him walking hand in hand with the girl's spirit.