While the plotline of The Scarlet Letter could have become moralistic under the pen of a more conventional author, Nathaniel Hawthorne's ambivalence regarding his characters creates a greater richness of characterization. Hester and Dimmesdale are not present as wholly good for their love nor wholly depraved for their adultery. Pearl is both Hester's joy and trial. Even Chillingworth's emotions hint at motives that go beyond plain villainy.
While Hester and Dimmesdale's adulterous liaison is presented as sinful, Hawthorne refrains from judging either harshly. Indeed, one can empathize with Hester's decision: she is young, passionate, and neglected by a much older husband she does not love. Better yet, she matures as a result of her suffering, choosing to become more charitable and patient rather than lash out as Chillingworth does. Dimmesdale is less sympathetic, mainly due to his cowardice, but even this is tempered by his guilt-ridden conscience, compassion, and genuine goodness towards his community. Ultimately, neither lover is overly demonized or romanticized.
Pearl is perhaps the most ambivalently presented character. She is a precocious child given to wild fits of emotion. While she gives Hester's life meaning in her social exile, she is also willful and passionate, a living embodiment of Hester's shame. Pearl is often described in pagan terms such as "elf-child," creating a sinister ambiance around her. Her existence is wholly due to Hester and Dimmesdale's sin, and yet she is also a great comfort to her mother, who might have lived a loveless life with Chillingworth otherwise.
While Chillingworth is rendered less sympathetic than the lovers, Hawthorne still gives the reader a notion as to why he is the way he is. Before marrying Hester, he was an isolated scholar who was distant but otherwise amiable enough, but rage over Hester's betrayal warps him into a vengeful monster. While his reaction is never justified, it is a human one rather than the result of Chillingworth simply being wicked by nature.
Hawthorne's ambivalence regarding his characters allows the moral center of The Scarlet Letter greater poignancy and conviction. He is not presenting a world of moral absolutes, as in melodrama, but rather a world populated by flawed people who are free to choose good or evil at every opportunity.