It is Thoreau's belief and faith in the individual that helps animate his own sense of personal understanding and philosophy. Seeking to develop and articulate a philosophical foundation that extols the virtue of the individual away from the mass element of social settings, it is this sense of solitary identity that compels Thoreau to break away from conformist ways. This idea of the individual being able to speak and act in such a manner helps to reconfigure the individual's association with nature, a setting where the true sense of self can be revealed. At the same time, this individualism helps to feed Thoreau's understanding of politics, suggesting that individuals have a moral and political obligation to act in accordance to their conscience and not stand idly by if their government is acting in a manner against this duty.
To use his own words, Henry David Thoreau "marched to the beat of a different drummer." A veritable individual and original thinker, Thoreau went into the woods in order to ponder the meaning of his existence; he went deliberately in order to learn from Nature, and to
front the essential facts of life, and see if I could not learn what it had to teach, and not, when I came to die, discover that I had not lived.
While in the woods, Thoreau observed warring ants and praises their "pertinacity." During his encounter with a loon, Thoreau is outsmarted by nature:
But why, after displaying so much cunning, did he invariably betray himself the moment he came up by that loud laugh?
He left the woods, he declared, for much the same reason; he had begun to fall into the most trivial of pursuits:
It is remarkable how easily and insensibly we fall into a particular route, and make a beaten track for ourselves.
On political issues, Thoreau was thoroughly an independent thinker, as well. This independence and fearlessness of Thoreau's nature led him to speak out actively according to his moral sensibilities. For instance, he supported the Abolitionists long before doing so had any popularity. In 1845, following the example of Louisa May Alcott's father, Bronson Alcott, Thoreau went to prison rather than pay a poll tax to a government that "countenanced war and slavery." His quiet resistance to what he considered an oppressive government influenced great leaders such as Mohandas Gandi and Martin Luther King, Jr. who practiced the same passive resistance.
Clearly ahead of his times, Thoreau was not appreciated for his thinking until after his death. To this day, there is a Thoreau society that works toward the preservation of Walden and other natural areas.
Thoreau's major involvement in literature took place during the Transcendental movement. This era brought in ideas of non-conformity, finding one's self, and reflection of the soul to name a few issues.
Nature: Thoreau thought it best to take every advantage of nature possible. His work Walden placed him in situations to imagine a piece of land and what he would do as a farmer given the opportunity. The experience of Walden removed him from society and positioned him to try to live meanly off the land. He wanted to live deeply and suck all the marrow out of life.
Politics: Thoreau seemed to not have time for things that enveloped that which made a man quest for power, although he did believe people had certain rights they should be able to pursue. His work Civil Disobedience reflected this belief.
I recommend a quick read of a summary of both for further study.