The Scarlet Letter

It seemed to be his wish and purpose to mask this expression with a smile; but the latter played him false, and flickered over his visage so derisively that the spectator could see his blackness all the better for it. Ever and anon, too, there came a glare of red light out of his eyes; as if the old man's soul were on fire, and kept on smouldering duskily within his breast, until, by some casual puff of passion, it was blown into a momentary flame...
In a word, old Roger Chillingworth was striking evidence of man's faculty of transforming himself into a devil, if he will only, for a reasonable space of time, undertake a devil's office...
The scarlet letter burned on Hester Prynne's bosom. Here was another ruin, the responsibility of which came partly home to her. (This passage was taken from page148 of The Scarlet Letter, by Nathaniel Hawthorne.)

After Chillingworth found out that Hester had betrayed him, he decided he wanted revenge. So, he turned himself into a monster being controlled by his evil desires of hate and bitterness and the lust for others to feel the pain he felt. Hester saw this monster that used to be her husband and felt as if it was her fault that this had happened. But it was not her fault. It was his choice! If he had forgiven her and Dimmesdale, forgotten the whole thing, and went on his merry way, none of this would have happened and Chillingworth would still be a respectable scholar and doctor. He could have been like Hester who forgave the community and still helped them even though they gave her the scarlet letter. Choices, choices, choices...

Comments
subject: Nathaniel's subject was the fact that Chillingworth had turned himself into a monster and Hester felt it was her fault, even though Chillingworth chose to let his evil desires rule him.
purpose: Nathaniel's purpose was to help us to understand exactly what had happened to Chillingworth and that he was now the "bad guy" in the book.
audience: Nathaniel's audience was us, the intelligent people who now realize that Hester and Chillingworth chose different paths, but could have turned out the same way. Either Hester trying to take revenge on the town for giving the scarlet letter, or Chillingworth forgiving and forgetting what Hester had done.