(3)The destructive force of industrial progress

Thoreau began his life at Walden, when the Industrial Revolution was in full force. Its impact upon life is best illustrated in Walden by the locomotive which passes daily by the pond, its whistles and rumbling contrasting with the natural sounds of the birds. Village life now runs at a faster pace, "railroad time," leaving even less time for the contemplation of self and nature which Thoreau desires. Such "progress" has a negative impact upon people's lives and upon the environment, the purity of which it pollutes and destroys.

(4)The animal/spiritual dialectical struggle within man

Within himself and all men, Thoreau perceives two struggling natures one a wild, animal nature and the other a spiritual nature. It is this animal nature which occasions the impulse to catch and deliver a woodchuck raw and which he detects in its fullest form in the French-Canadian woodcutter. However, he seeks in himself and urges in his reader the perfection of the spiritual nature, through avoidance of meat and animalistic desires, and represents the struggle in himself through the imagined conversation between the Hermit (spiritual) and Poet (animal). Only within a few examples from the animal kingdom noble battling ants, the winged cat, and the loon can Thoreau see the animal and spiritual coexist peacefully.

(5)Nature as reflection of human emotions

More than once, Thoreau describes Walden Pond as a mirror. Throughout the novel, the weather continually reflects his emotional state. His period of melancholy and doubt occurs during the winter when the pond is frozen and nature is silenced, and his joy and exultation is reflected in the thawing of the lake and growth of new life in the spring. The daily and seasonal variations in the pond and surrounding environment parallel the variety of and changes in Thoreau's intellectual musings. The idea of nature reflecting human emotion supports Thoreau's belief in man as a part of, rather than separate from or above, nature.

(6)Spiritual rebirth reflected in nature and the seasons

Thoreau employs the repeated metaphor of rebirth throughout his book, as a means of convincing his readers to seek new perspective on themselves and the world. The cycle of the seasons, with the rebirth of the winter-dormant pond, animals, and plants in the spring, functions as the promise of an eventual spiritual rebirth in humans. Likewise, Thoreau's description of the hunter boy who grows to be a naturalist as a man and his metaphor of awakening from the slumber of life evince his hope and belief in the progress of human beings to a newer, greater understanding of themselves. He ends the book with a final metaphor of rebirth, describing the bug which hatched out of a wooden table after decades, in the hope that some day, even if not immediately such a rebirth will occur within human society.

(7)Discovery of the essential through a life of simplicity

In his first chapter, "Economy," Thoreau says that he went to the woods to describe what is truly necessary in life. Later, he says that he "went to the woods to live deliberately" so that when he died he would not find that he had never really lived. By ridding himself of the luxuries of society a big house, coffee, meat, even salt and yeast Thoreau discovers through his own "economy" what is really necessary to live a fulfilled life. His discovery of the relatively small amount of work needed to live in relative comfort leads him to attempt to convince his reader as well as John Field to similarly simplify their own lives and thus live more happily. For Thoreau, this is a happy discovery, for he comes to believe that one could be as happy in almshouse, with the same afternoon sun coming in the window as does in a rich person's house, as he would anywhere else. To his reader, Thoreau insists, "Simplicity! Simplicity! Simplicity!"

(8)Exploring the interior of oneself 梭罗的自然观对中国生态的反思Thoreau’s Views on Nature(4):http://www.youerw.com/yingyu/lunwen_932.html