insensibly
Careful writers of narrative, whether that narrative is fictional or historical or journalistic, will, like composers, work with themes and variations on those themes. For example, consider Edward Gibbon: reading his account of Rome’s decline and fall a few years ago, I noticed his fondness for a particular adverb: insensibly. “It was by such institutions that the nations of the empire insensibly melted away into the Roman name and people.” “We have already seen that the active and successful zeal of the Christians had insensibly diffused them through every province and almost every city of the empire.” “The heart of Theodosius was softened by the tears of beauty; his affections were insensibly engaged by the graces of youth and innocence: the art of Justina managed and directed the impulse of passion; and the celebration of the royal nuptials was the assurance and signal of the civil war.”
Why does Gibbon like this word so much? Is it just a verbal quirk? I think not: rather, it embodies a key theme of the whole history, which is that major transformations in the life of the Roman empire happened slowly, gradually, and without anyone noticing them: people were insensible to the changes, and by the time anyone figured out what had happened, it was too late for a reversal of course. And this insensibility affects political structures, social and religious developments, military cultures, and the hearts of emperors alike; this particular theme has many and wide-ranging variations.
The reader who notices this word, then, notices a vital, not a trivial, point about the story Gibbon tells.