Why does pearl see chilling worth and dimmesdale as potential incarnations of the devil-"black man"

Pearl does not have a clear view of what is good and what is evil. She is, however, very perceptive and wants to identify the "black man" as soon as she can. When Chillingworth comes out of the woods, she is convinced he might have come from some place where "black men" are found. She realizes that Dimmesdale has a problem when he clutches his heart repeatedly and is thus, at some level, suffering distress. Pearl wants to know what Mistress Hibbins is talking about and so she sees a possible "black man" in many of the men around.

When Hester meets Chillingworth in the forest, he has a blackness about him and a red light showing out of his eyes, as if "the old man's soul were on fire, and kept on smoldering duskily within his breast." The dark forest is also, so the Puritans thought, where the "black man" lives. Pearl asks her mother to tell her a story about the Black Man, who is said to haunt the forest. The Black Man is a myth about the devil, and the story says that he carries a large book and pen with which people write their names in blood. The Black Man then puts his mark on the person.

Hester, tired of Pearl asking about the scarlet letter, tells her that the letter is the mark of the Black Man, which she received after meeting the Black Man once before. Dimmesdale then starts coming down the forest path, and Pearl sees him. She asks her mother if he covers his heart because he has a mark on his chest as well. She further asks why he does not wear his mark on the outside of his clothing like her mother does. PLease check out this excerpt from the GradeSaver Site in the source-link below.