According to my understandings, there are two reasons for Hooper to wear a black veil. He wears it for secret sin and self-salvation. First of all, he wears it to remind himself of his sin unknown to others. In the text, it seems that Hooper has some improper relationship with the dead young lady. Therefore, he wears the black veil to uncover and admit his sin. Secondly, self-salvation is the major reason for him to wear it. Aware of his sin, Hooper hopes to save himself from conscience criticism and spiritual suffering through putting a black veil in front of his face. He confesses his sin in order to deduce his sense of guilty.
Taken what’s discussed above into consideration, it’s easy to notice that the black veil symbolizes Hooper’s sin. Besides, it also symbolizes the general sins hidden in everyone’s heart. People are fearful and frightened when seeing the minister wearing a black veil because they are afraid that he may discover the secret sins that are hidden inn their heart. “I look around me, and lo!on every visage a Black Veil.” The last sentence of the minister also shows that everyone has secret sins, but they are not bold enough as him to wear a black veil to admit them.