There is much that Thoreau learns from his short time in jail about both his town and his relationship to the government. Thoreau gets thrown in jail because he has refused to pay the poll-tax for a number of years. A poll-tax is a tax that every individual is required to pay, regardless of their income. Thoreau is not keen on being "required" to do anything by the government, and thus he claims to have not paid the tax on principle, to protest the war with Mexico.

Of course, once put in jail, Thoreau feels that he has been treated unjustly. He writes, "I could not help being struck with the foolishness of that institution which treated me as if I were mere flesh and blood and bones, to be locked up." While Thoreau recognizes the power that his government holds over him, he feels that this should not be so, that individuals should be free to act as they choose. Acting according to one's nature is crucial to Thoreau, and, while recounting his prison experience, he makes the following analogy: "If a plant cannot live according to its nature, it dies; and so a man." People, Thoreau implies, are products of nature just like plants, and, also like plants, they must live according to their nature. Otherwise, they will cease to exist.

Despite feeling that he has been treated unfairly, Thoreau does not seem to mind prison too much and actually does a fair bit of learning. He comes to understand how his town functions by listening to its sounds from his prison cell. He says,

It was like travelling into a far country, such as I had never expected to behold, to lie there for one night. It seemed to me that I never had heard the town-clock strike before, nor the evening sounds of the village; for we slept with the windows open, which were inside the grating...

It was a closer view of my native town. I was fairly inside of it. I never had seen its institutions before. This is one of its peculiar institutions; for it is a shire town. I began to comprehend what its inhabitants were about.

In other words, by living in the cell, on the margins of a society, Thoreau was able to gain a better understanding of how his society operated. He learned its rules, patterns, and customs and gained knowledge of its "institutions." This proved to be a valuable experience for Thoreau, despite his aforementioned protests.

Henry Thoreau learned much about (a) the experience itself, (b) the townspeople’s reactions to it, (c) and, in more general terms, the relationship of the individual to and with his government.

The Middlesex County jail sat right in the middle of downtown Concord, just off the common and behind the Middlesex Hotel. Even though he had probably walked past the place many times, Thoreau had never spent a night in that part of town before. The experience was almost as enlightening as finding a new plant in a swamp. “It was like traveling into a far country, such as I had never expected to behold,” he says in paragraph 30. Through the open but grated window, he heard the town clock strike the hours. He heard voices from people on the street. He heard the hustle and bustle of activity in the hotel kitchen next door. “It was a closer view of my native town. I was fairly inside of it. I never had seen its institutions before.” This was a unique and interesting experience for him. He didn’t seem worried about his fate.

When Thoreau was released the next morning, he felt as though he had been at least slightly changed by the incident. His Aunt Maria had probably been the one to pay the poll tax for him. But none of his other fellow townspeople seemed to even care. He throws a fair amount of criticism at them in paragraph 32:

I saw to what extent the people among whom I lived could be trusted as good neighbors and friends; that their friendship was for summer weather only; that they did not greatly propose to do right; that they were a distinct race from me by their prejudices and superstitions … This may be to judge my neighbors harshly; for I believe that many of them are not aware that they have such an institution as the jail in their village.

He says that it had been a custom to greet someone coming out of jail with a hello and a salute. No one did this for Thoreau. Instead, they “first looked at me, and then at one another, as if I had returned from a long journey” (paragraph 33). He understood then that most of them did not understand the way the law worked, or if it worked at all. They just blindly followed it, without question.

One of the realities he grasped about the legal aspect of the incident was that the government had no recourse set up for anyone who disagreed with the law. You either obeyed it, or you were arrested and put into jail. Earlier, in paragraph 16, Thoreau says that whenever citizens believe that laws are unjust, they think they have to wait to have a majority of others to join with them in order to protest or overthrow it. If they try to protest a law by themselves – as Thoreau did – they believe that “the remedy would be worse than the evil.” In other words, they would have to judge for themselves which would be worse: “the remedy” of going to jail for their effort, or “the evil” of living under the law they disagree with. Why doesn’t the government have a method put in place for those who want to protest on their own? Thoreau asks.

Why is it not more apt to anticipate and provide for reform? Why does it not cherish its wise minority? … Why does it not encourage its citizens to be on the alert to point out its faults, and do better than it would have them?

Unfortunately, this is one lesson from his overnight experience for which he could get no good answer.