In Hawthorne's The Scarlet Letter, in Chapter 11—entitled "The Interior of a Heart"—the theme I find most prevalent is the dichotomy of sin. Sin has the power to destroy but also to transform. Such is the case with Roger Chillingworth. His sin of jealousy has transformed him into a man intent not just on revenge, but in a long-suffering revenge, visited on Rev. Dimmesdale.
Calm, gentle, passionless, as he appeared, there was yet, we fear, a quiet depth of malice hitherto latent, but active now, in this unfortunate old man, which led him to imagine a more intimate revenge than any mortal had ever wreaked upon an enemy.
Chillingworth allows his own disappointments and suffering to turn him into a sinner equal and perhaps even surpassing Dimmesdale, in that Chillingworth is maliciously inclined to harm, where Dimmesdale's sin was never of that kind. (Though theologically, sin is sin, without degrees of "sinfulness.")
While Chillingworth' soul is deteriorating in his state of sinfulness, Dimmesdale, while declining in his physical health, not only becomes more devoted in atoning for his sin, but is inspiring his congregation all the while. This may not be his intent, but the way he lives his life is uplifting to the members of the church. As he becomes more guilt-ridden, he is being purified like gold in a fire. Dimmesdale's torment can be understood by studying his respect for the truth and how he despises a lie:
...by the constitution of his nature, he loved the truth, and loathed the lie, as few men ever did. Therfore, above all things else, he loathed his miserable self!
As "Interior of a Heart" implies, this chapter gives us the chance to look within the hearts of the two men connected to Hester. Chillingworth loses his soul to the sin that eats at him from within. Ironically, the man of the cloth—who knows of his own sin and suffers greatly for it—is closer to God's will in that he recognizes his sin—which Chillingworth does not—and spends long, painful hours in penitence. In deed, from Dimmesdale comes something valuable, even in light of sin.
Sin transforms both men: Chillingworth loses sight of his moral direction, ironically falling off the same ethical platform from where he stood to so harshly judge Dimmesdale's sin. Dimmesdale, on the other hand, perpetually atones for his sin, and turns his life around while more powerfully reaching out to his congregation because of his fall from grace and his remorse.