Answer:
I believe the theme of this story is that truth is sometimes better left unsaid[or "truth kills"]. Like in this story, the guy loved this woman and thought she had loved him back. He would have never thought that she would go out and try to deceive him. He would have lived happier, if he thought that she was still faithfully clinging and loving him silently even in death. Yet he was very oblivious and curious to know the truth of why she had died, and that truth eventually killed him.
It's known as abstract nouns
Quindlen links the conclusion to the introduction of her essay with the words "like many improbable ideas, when it works, it's a wonder", which is very close to her claim in the overall text, "America is an Improbable idea", it isn't supposed to work but it does despite all of the differences, specifically racial or ethnic, within it.
To all look like each other
