What does this statement from chapter XVIII mean? Sin "had been a sin of passion, not of principle, not even purpose"
Near the beginning of chapter XVIII, Hawthorne says that Dimmesdale's sin "had been a sin of passion, not of principle, not even purpose." What does this statement mean?
Since this follows the chapter where Hester and Dimmesdale get together for the first time in 7 years, it provides an interesting comment on their sin as compared to Chillingworth's. Hester has just suggested that "what we did" (no mention of sin or even of something that was wrong, just what we did) had a "consecration" of its own. She is speaking of an act of adultery in religious terms of the sacred act in a Catholic Mass. Sins of passion tend to be things that we are "hard wired" for, that are part of our chemistry, and adultery is one of these.
On the other hand, the sin of Chillingworth is not tied to any chemistry, but is rather of principal and purpose --- it is the calculated decision to destroy another human being. Dimmesdale, guilt ridden though he is, knows it:
That old man's revenge has been blacker than my sin. He has violated, in cold blood, the sanctity of a human heart. Thou and I, Hester, never did so!"
This distinction introduces two concepts. One is that all sins are not the same, that sins of revenge, sins of calculation, are much worse than sins of passion. It also introduces the concept of the individual making decisions about morality outside the "iron framework" of the church, separating church and state in a way that it is not at the start of the novel where they are identified as one and the same.
Sin of passion is considered a "low" kind of sin. As the story is set during the early times where everything and everybody have to be conservative and submissive (especially women). The people only consider things dealing with reason, knowledge, tradition and principle to be appropriate and worthy of their time. On the contrary, they see passion emotions to be jokes, foolishness, and waste of effort. And so, since the story deals with adultery, the characters in the story deem that "sin of passion" to be something unworthy. Therefore, they think that they should spend their time and effort over it. Surprisingly enough, they do not disregard these kinds of issues. Although they deem it to be of a low kind and status, they immediately cast it as a curse and therefore, should be banished.