Emerson states his themes pretty straightforwardly. He outlines a number of nature's beneficial effects on human beings and how it seems to even restore us to a better and more fundamental version of ourselves. It is clear that human beings thrive only when we allow ourselves to go out into nature and experience its myriad benefits on our bodies and minds and souls. Emerson says, in part,

In the woods, we return to reason and faith. There I feel that nothing can befall me in life,—no disgrace, no calamity, (leaving me my eyes,) which nature cannot repair. Standing on the bare ground [...] all mean egotism vanishes. I become a transparent eye-ball; I am nothing; I see all; the currents of the Universal Being circulate through me; I am part or particle of God.

In nature, then, we become our best selves. Our egos seem to dissolve and we recognize the divinity in our own natures. We no longer see only "I" that we typically identify as, the self-centered and selfish self, but, rather, how we are connected to God and nature around us, everywhere. Emerson offers further evidence of this relationship between ourselves and all of nature when he describes the "occult relation between man and the vegetable." Emerson believes in a divine trinity of nature, humanity, and God; we are all connected and there is a spark of the divine within each of us. This means that we can recognize this spark within elements in nature just as they can recognize the spark of divine within us too. In nature, Emerson says, "I am not alone and unacknowledged." This idea, of the connection among all things on the earth is paramount to Emerson's essay.

In "Nature," Emerson ties together two themes that are dear to his heart: individualism and nature. A person can find his (Emerson addresses an imagined male) best self, his individual destiny, and his spiritual/creative path through the world by immersing in, contemplating, and developing a harmonious relationship with nature.

Emerson rejects what he calls the "sepulchers" of looking to the past and old tradition for wisdom. All natural things, he argues, are fresh and can teach us with newness and vigor in the here and now. We can get everything we need to guide our lives through a communion with nature in the present moment that will lead us inward to our souls. In nature, we will become in touch both with ourselves as individuals and with the divine spirit of the universe that should be our central guide. Emerson repeatedly exalts nature in the essay.

Like Wordsworth, Emerson believed the child was born with the inward light and capacity to perceive truth that comes from the divine. We gradually lose this as we grow older, but we at our best and most able to achieve to our highest capacity where we are able to retain a child's wonder and harmony with nature:

The lover of nature is he whose inward and outward senses are still truly adjusted to each other; who has retained the spirit of infancy [early childhood] even into the era of manhood.

The great thing about Emerson and other transcendentalists is that they weave together several main themes throughout their writing. This leads to great discussions among students regarding what the "main" theme is. Some students lean toward thinking Emerson is emphasizing nature and its power to teach. Other students lean toward Emerson's emphasis on individuality. Both of those themes are in line with the tenets of transcendentalism, so both can be defended as the main theme.

Woven throughout those two themes is a strong sense of "carpe diem". Emerson argues that any individual that seeks to know about God, the universe, nature, and so on needs to get out into the world and explore nature as much as possible—and as soon as possible. The individual seeking and gaining knowledge for himself is paramount for Emerson.

To go into solitude, a man needs to retire as much from his chamber as from society. I am not solitary whilst I read and write, though nobody is with me. But if a man would be alone, let him look at the stars. The rays that come from those heavenly worlds, will separate between him and what he touches.

The central theme of Emerson's essay "Nature" is the harmony that exists between the natural world and human beings.

In "Nature", Ralph Waldo Emerson contends that man should rid himself of material cares and enjoy an original relation with the universe and experience what he calls "the sublime." (The "sublime" is closely connected to the divine.) When man's mind is open to the influence of nature, he can sense "a wild delight" as he can "cast off his years" and the cares of the times in which he lives. He can, then, become a child again and love the "immortal beauty" of nature, experiencing the pleasure and fulfillment that this love of nature provides. Emerson comes closest to stating his theme of the harmony of the natural world and man in his essay with this passage:

The lover of nature is he whose inward and outward senses are still truly adjusted to each other[...]. His intercourse with heaven and earth, become part of his daily food.

As a Transcendentalist, Emerson believed that people should take themselves away from their daily cares and reach a contemplative state which permits them a connection with the divine. The beautiful fields of flowers, the awe-inspiring woods, "the waving of boughs in a storm," and the magnificence of the stars produce a delight in man that inspires him and connects him with the "sublime presence." Indeed, Emerson connects man and the natural world in this experience of the sublime. For when man and nature are in harmony, "Nature always wears the colors of the spirit."