Why does Hawthorne begin the story with a reflection about the need for a cemetery and a prison?

In "The Scarlet Letter", Nathaniel Hawthorne uses the metaphors of prison and a cemetery to stand for two types of enslavement or imprisonment. The first is physical, in this we need only look at the fate of Hester and the innocent, Pearl, both of whom are forced to bear visible signs of sin (The letter "A" and illegitimacy) that subject them to isolation, as if in prison. The second is spiritual imprisonment, which could be used to describe what Dimmesdale goes through until he is able to free himself of his spiritual prison by confession and redemption by death (the cemetery).