6 ideas
The cost of a thing is the amount of life that must be exchanged for it, immediately or in the long run. Measured this way, a larger house or a finer coat has to be paid for with years of labor. The frugal person who wants little is therefore richer in free time than the prosperous farmer who owns much.
People take on inherited farms, mortgages and customs without testing whether these serve them, and then work to maintain them. Because this entrapment is conventional, it is felt as resignation rather than recognized as a choice. The remedy is to examine from first principles which necessities of life are actually required: food, shelter, clothing and fuel.
Thoreau built his cabin for $28.12½ and published an itemized ledger of his building costs, his bean-field and his food. He showed that about six weeks of work a year could cover a person's living expenses. The ledger turns a philosophical claim into a testable experiment and satirizes the account-keeping of commercial life.
Go to a situation stripped of nonessentials so that you face only life's basic facts, and then observe what they teach. If life proves mean, you get its full meanness. If it proves sublime, you know it by experience. The key instruction is 'Simplify, simplify': reduce the number of your affairs so your attention is not frittered away on detail.
Thoreau sounded Walden Pond to disprove the legend that it was bottomless, and he read its clarity, color and depth as the 'earth's eye.' Close attention to one bounded natural place becomes a way of measuring one's own nature. The particular, observed patiently, opens onto the general.
The patterns of thawing sand and clay flowing down a railroad cut resemble leaves, veins and organs. From this Thoreau argues that the earth is living and that the leaf is nature's basic form. The yearly return of spring shows that rebirth is a law of nature, so a person can also shed an old life and start again.