This movement toward spiritual perfection, the main movement of Walden, is expressed through metaphors. When the narrator starts to construct his cabin in March 1845, he also, metaphorically, informs the reader that he is beginning to "build" a new self and a new life. As he proceeds, signs of rebirth and renewal suddenly appear. He tells us that "the ice in the pond was not yet dissolved," but as he works at his cabin ("builds" a new self), the iced pond (signifying his state of spiritual rigidity and lifelessness) continually thaws. The narrator makes clear this significant correspondence between the thawing ice and his own movement out of a spiritual "winter": "They were pleasant spring days, in which the winter of man's discontent was thawing itself as well as the earth, and the life that had lain torpid began to stretch itself." Nature "spring-ing" to life thus becomes a metaphorical expression of the new vitality the narrator was coming to feel. Next, he mentions a snake that ran into the pond and "lay on the bottom . . . more than a quarter of an hour; perhaps because he had not yet fairly come out of the torpid state" of winter hibernation. The narrator sees this half-awake snake as significant of his and other men's spiritual states. He finds hope for himself and others in considering that eventually the snake will be thawed by the sun; likewise, he and all men may be awakened from "their low and primitive condition" if they allow themselves to feel the revivifying power of nature. He proclaims his belief that men "should feel the influence of the spring of springs arousing them"; if they do, he says, "they would of necessity rise to a higher and more ethereal life." The narrator is now moving toward this higher state of life, signaled by the song of "one early thrush." In Thoreau's writings, the songs of birds, particularly the thrush, are often used to symbolize inspiration.
Metaphors of rebirth are also used in the narrator's discussion of clothing and furniture. In criticizing man's obsession with fancy clothing and the fact that most people judge a man by his appearance rather than by the quality of his character, he indicates his own concern for the inner being that exists beneath the external shell. Man should first concern himself with the growth of inward perfection, since true beauty is born within the soul. To illustrate this, he turns to the natural phenomena of rebirth and renewal and points out that natural, true beauty must grow from within and cannot be externally applied: the "new" snake emerges from the old skin in the spring after having developed his new skin within the old; the caterpillar achieves its butterfly state by withdrawing and completing itself within its cocoon; and the loon renews its appearance by molting, shedding its old feathers, and growing new ones. As animals transform themselves into more beautiful, more perfect creatures through internal growth, so must man concern himself with casting off the old, imperfect self and creating a new, more perfect one within if he is to become spiritually beautiful.
