In late 1849, two years after Henry David Thoreau left Walden Pond—where he had lived for two years, two months, and two days in a cabin that he had built himself—he began the process of completely reorienting his life again. His hermit-style interlude at the pond had attracted quite a bit of attention in his hometown of Concord, Massachusetts. “Living alone on the pond in ostentatious simplicity, right in sight of a main road,” his latest biographer, Laura Dassow Walls, writes, “he became a spectacle,” admired by some and belittled by others. Thoreau’s subsequent life change was less conspicuous. Yet it engaged him in a quest more enlightening and relevant today than the proud asceticism he flaunted throughout Walden, a book that has never ceased to inspire reverence or provoke contempt.

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What the 32-year-old Thoreau quietly did in the fall of 1849 was to set up a new and systematic daily regimen. In the afternoons, he went on long walks, equipped with an array of instruments: his hat for specimen-collecting, a heavy book to press plants, a spyglass to watch birds, his walking stick to take measurements, and small scraps of paper for jotting down notes. Mornings and evenings were now dedicated to serious study, including reading scientific books such as those by the German explorer and visionary thinker Alexander von Humboldt, whose Cosmos (the first volume was published in 1845) had become an international best seller.

As important, Thoreau began to use his own observations in a new way, intensifying and expanding the journal writing that he’d undertaken shortly after graduating from Harvard in 1837, apparently at Ralph Waldo Emerson’s suggestion. In the evening, he often transferred the notes from his walks into his journal, and for the rest of his life, he created long entries on the natural world in and around Concord. Thoreau was staking out a new purpose: to create a continuous, meticulous documentary record of his forays. Especially pertinent two centuries after his birth, in an era haunted by inaction on climate change, he worried over a problem that felt personal but was also spiritual and political: how to be a rigorous scientist and a poet, imaginatively connected to the vast web of natural life.

Thoreau’s real masterpiece is not Walden but the 2-million-word journal that he kept until six months before he died. Its continuing relevance lies in the vivid spectacle of a man wrestling with tensions that still confound us. The journal illustrates his almost daily balancing act between recording scrupulous observations of nature and expressing sheer joy at the beauty of it all. Romantic predecessors like Samuel Taylor Coleridge and, centuries before that, polymaths like Leonardo da Vinci thrived on the interplay between subjective and objective exploration of the world. For Leonardo, engineering and math infused painting and sculpture; Coleridge said that he attended chemistry lectures to enlarge his “stock of metaphors.”

For Thoreau, along with his fellow Transcendentalists, the by-now familiar dichotomy between the arts and the sciences had begun to hold sway. (The word scientist was coined in 1834, as the sciences were becoming professionalized and specialized.) Thoreau felt the disjunction acutely, and his journal lays bare both his fascinated scrutiny of the most intricate factual details and his fear of losing his grasp of nature or the cosmos as a whole.

Today scientists churn out data-stuffed reports assessing the perils we face—shrinking Arctic ice, rising sea levels, extreme floods and droughts, the acidification of oceans, forest fires. Their daunting graphs, tables, and technical language stir up debates and doubts. Such dry projections, devoid of poetry and imagination, serve as an implicit summons to experts to come up with solutions. Crucial though the data and reports are, they eclipse precisely the sort of immediate, intuitive, sensual experiences of nature that are, in our Anthropocene era, all too rare. For Thoreau, a sense of wonder—of awe toward, but also oneness with, nature—was essential. We will, he understood, protect only what we love.

On the bicentenary of his birth, Thoreau the journal writer is in the limelight. “This Ever New Self: Thoreau and His Journal,” an exhibit that began at the Morgan Library, in New York, is now at the Concord Museum through early 2018. Eight of a projected 17 volumes of the journal have been published by Princeton University Press so far, and the transcripts and copies of the others are available online. For those daunted by the millions of words, selections of Thoreau’s observations on trees, wildflowers, and animals stand out in the recent flurry of publications and offer a fascinating taster.

In her comprehensive Henry David Thoreau: A Life, Walls—who has previously written about Thoreau’s “turn to science”—calls attention to the pivotal moment when he began to use his journal as he never had before. On November 8, 1850, a year or so after his naturalist’s regimen had begun, Thoreau “wrote up everything he noticed and thought during his daily walk as one long entry.” He did the same the next day, and two days later, Walls notes, and then again a couple of days after that, and the next day,

filling pages with a stream-of-consciousness flow of words as if he were writing while walking: “I pluck,” “I heard,” “I saw yesterday,” “I notice.”

“And this is what truly staggers the mind,” Walls goes on. “From this point, Thoreau did not stop doing this, ever—not until, dying and almost too weak to hold a pen, he crafted one final entry.”

University of Chicago

A week after that first extended entry, he wrote, “I feel ripe for something; it is seed time with me—I have lain fallow long enough.” Thoreau went on, “My Journal should be the record of my love.” At the same time, his journal was a repository of constant measurements, minute and expansive: of the depth of streams, the wingspan of a moth, the number of bubbles trapped beneath the frozen surface of the pond. “What are these pines & these birds about? What is this pond a-doing? I must know a little more,” Thoreau had written back in 1846, when his journal had still been a source to plunder for other writing projects, not yet a compendium of exhaustive field notes. Now his quest for unifying order became more focused, and he set out to pursue it by counting the petals on a blossom or the rings in the stump of a fallen tree—hoping not to lose a sense of beauty and mystery in the process.

The tension between the particular and the whole wasn’t new. Transcendentalists like Emerson were searching for unity in nature, but resisted what seemed to them the blinkered reliance on deductive reasoning and empirical research enforced by encroaching science. Such methods tended to “cloud the sight,” Emerson said, and he endorsed instead a conception of nature as “the symbol of spirit.” That Emersonian notion of natural phenomena as the embodiment of what his mentor called “ideas in the mind of God” had once thrilled Thoreau, as Walls writes. But by the time Thoreau reoriented his life, he needed more direct contact with the “marrow of nature.” Thoreau had already framed the poet-scientist dilemma in 1842, when he reviewed a series of natural-history reports published by the State of Massachusetts: How could such dry summaries hold any interest for the general reader? Where, Thoreau asked in his review in the Transcendentalist literary magazine The Dial, was the joy of nature?

Reading Humboldt’s most popular books, Cosmos, Views of Nature, and Personal Narrative, during his evenings of study, Thoreau learned a way of weaving together the scientific and the imaginative, the individual and the whole, the factual and the wonderful. A vast array of observations, Humboldt insisted, revealed “unity in diversity”—each fact and detail of nature threading together into an interconnected whole. Even before he adopted his systematic regimen, Thoreau’s journal—packed with observations about the songs of birds, the chirping of crickets, the careless pace of the fox, the scent of musk, the “dreamy motions” of fish’s fins—was proof of his visceral relationship to nature. In Thoreau and the Language of Trees, the writer Richard Higgins describes Thoreau sniffing the bark of twigs, listening to the creaking of hardwoods in winter, sampling the taste of lichens (he liked rock tripe and Iceland moss best), delighting in the play of light and shadow in the canopy of trees.

University of California

“We must look a long time before we can see,” Thoreau had concluded in his Dial essay on the “Natural History of Massachusetts,” pronouncing that “the true man of science … will smell, taste, see, hear, feel, better than other men.” Moving beyond Emerson’s grand and spiritual ideas of nature, Thoreau became part of a lively scientific discourse, aware of the latest discoveries, and he used the libraries at Harvard and the Boston Society of Natural History extensively. He collected fish specimens for the zoologist and geologist Louis Agassiz at Harvard. And though he was a little squeamish about gathering birds’ eggs for another scientist there, he agreed to commit “deliberate murder” if the advancement of science demanded it.

Thoreau was anxious to get the balance right. “This habit of close observation—in Humboldt—Darwin & others. Is it to be kept up long—this science?” he asked himself. As Walls noted in her previous book about Thoreau’s relationship to 19th-century science, Seeing New Worlds, his reading of Charles Lyell’s revolutionary Principles of Geology in 1840 had given him the insight that small details add up to one bigger truth: Lyell argued that the Earth had been shaped gradually by minute changes, and that these slow forces were still active. Steeped in the sciences, Thoreau emphasized that orderly data needn’t be dead. Carl Linnaeus’s binomial system for classifying plants was “itself poetry,” and in the early 1850s Thoreau jotted in his journal, “Facts fall from the poetic observer as ripe seeds.”

Still, Thoreau felt the limits of disciplined scrutiny. “With all your science can you tell how it is, and whence it is, that light comes into the soul?” he asked in one of his July 1851 entries. In December, when he saw a crimson cloud hanging deep over the horizon on a cold winter day, he wrote, “You tell me it is a mass of vapor which absorbs all other rays,” only to lament that this was not a good enough explanation, “for this red vision excites me, stirs my blood.” What kind of science was this, he wanted to know, “which enriches the understanding but robs the imagination?” The following summer he summed up the dilemma. “Every poet has trembled on the verge of science,” he wrote after a long day at the Sudbury River, even as he also noted, “I wanted to know the name of every shrub.” Was his knowledge becoming so fine-grained “that in exchange for views as wide as heaven’s cope I am narrowed down to the field of a microscope”? He saw “details not wholes,” and feared being “dissipated by so many observations.” Or could the sensual be entwined with the scientific? For Thoreau, in a short entry about frogs, that happened: “They express, as it were, the very feeling of the earth or nature. They are perfect thermometers, hygrometers, and barometers.”

Humboldt had addressed the same issues. Nature, the undaunted explorer explained, should be described with scientific accuracy but without being “deprived thereby of the vivifying breath of imagination.” The same man who had carried 42 scientific instruments along on his five-year exploration of Latin America, from 1799 to 1804, also wrote that “what speaks to the soul, escapes our measurements.” To Goethe he later said, “Nature must be experienced through feelings.”

Out of Humboldt’s extensive travels and intensive investigation of similarities, differences, and interrelationships among organisms—and among humans and the world they inhabit—emerged his vision of what he called “a wonderful web of organic life,” today a given, but then a sweeping new insight. In this interwoven world where “everything is interaction and reciprocal,” Humboldt wrote, humans were bound to leave their mark on nature. Half a century before Thoreau wrote about the preservation of the wilderness, Humboldt warned that mankind was “raping nature,” and described the devastating environmental effects caused by monoculture, irrigation, and deforestation.

For Thoreau, Humboldt’s global vision galvanized a more personal, provincial approach to experiencing the vast living organism that was nature. A little stream in Concord was his stand-in for Humboldt’s thundering Orinoco River, the neighboring hills became Thoreau’s Andes, and according to Emerson, the Atlantic Ocean was for Thoreau “a large Walden Pond.” As he surveyed his smaller domain, Thoreau could sound supremely anthropocentric: “What is nature unless there is an eventful human life passing within her?” he wrote at one point. “Nature nought without human experience,” he jotted at another. But Thoreau could also adopt a less domineering voice—in Walden he famously asked, “Am I not partly leaves and vegetable mould myself?” He was deeply interested in what he called “the mysterious relation between myself and these things.”

This relationship between him and the natural world around him—this sense of synchrony—lay at the heart of his daily, monthly, yearly monitoring of the changing seasons. In 1851, he began to compile long lists of leafing-out and flowering times. As summer came, Thoreau wrote that he now thought of the journal as “a book of the seasons.” The full implications of this were gradually revealed to him. “For the first time,” he wrote on April 18, 1852, “I perceive this spring that the year is a circle.” This might not sound very revelatory to us today, and of course painters and poets had for centuries depicted the seasons, portraying wild autumn storms and lush spring meadows. But Thoreau’s tracking of cyclical change was a radically different endeavor, and the beginning of a truly ecological understanding of the natural world, years before the term ecology was coined in 1866, by the German scientist Ernst Haeckel (another admirer of Humboldt’s ideas).

“Make a chart of our life, know how its shores trend, that butterflies reappear and when—know why just this circle of creatures completes the world,” Thoreau noted in 1852. Over time, nature’s interrelationships and the planet’s regenerative power emerged for him. The seasons became a metaphor of Earth as a living organism, a planet thumping with life—even in the darkest depth of winter: “There is nothing inorganic,” he wrote; “this earth is not, then, a mere fragment of dead history … but living poetry like the leaves of a tree—not a fossil earth—but a living specimen.”


Thoreau the observer was also a passionate participant, and his cyclical attunement comes across vividly in two beautifully illustrated books, Thoreau’s Animals and Thoreau’s Wildflowers, containing journal extracts selected by the writer Geoff Wisner. Thoreau’s own yearning for rebirth was clear as he listened to a red-winged blackbird “calling the river to life and tempting ice to melt and trickle like its own sprayey notes. Another flies over on high—with a tschuck and at length a clear whistle. The birds anticipate the spring—they come to melt the ice with their songs.”


Always alert to the bonds that connected each individual plant, bird, and frog to the greater cosmos, he was stirred by the sound of the first bullfrog in May—the sign for him that summer had finally arrived: “I hear in his tone the rumors of summer heat. By this note he summons the season … it reminds me at once of tepid waters—and of bathing. His trump is to the ear what the yellow lily or spatterdock is to the eye.”

Thoreau was deeply affected by the rhythm of the natural world, and his urgent anticipation of renewal is everywhere. His moods, he said, were “periodical” and “the seasons and all their changes are in me.” He worried in mid-August about winter: “How early in the year it begins to be late.” And then in late October, it was almost as if he had to remind himself of the beauty of scarlet oaks’ fiery foliage in order to escape his impending winter melancholy: “Look at one completely changed from green to bright dark scarlet—every leaf, as if it had been dipped into a scarlet dye, between you and the sun. Was this not worth waiting for?” When the darkness arrived, his mood sank, and on a cold mid-November afternoon, he wrote:

The landscape is barren of objects—the trees being leafless—and so little light in the sky for variety. Such a day as will almost oblige a man to eat his own heart. A day in which you must hold on to life by your teeth. You can hardly ruck up any skin on nature’s bones. The sap is down—she won’t peel … Truly a hard day, hard times these. Not a mosquito left. Not an insect to hum. Crickets gone into winter quarters. Friends long since gone there—and you left to walk on frozen ground, with your hands in your pockets.

Yet even this entry shows how he considered himself an integral part of the natural world, the ecological community—a lonely traveler missing his old friends from summer. There is nothing reminiscent here of the haughty and sanctimonious Thoreau who is folded into the pages of Walden. In his journal, the punctilious scientist revealed himself as an observer whose soul was open to immediate connection with the big messy web of life: The sounds, colors, and smells of the seasons triggered emotions without a need for elaborate explanations. Nature, he wrote in January 1852, “is a plain writer, uses few gestures, does not add to her verbs, uses few adverbs, uses no expletives.” He aspired to do the same.

Thoreau wondered whether anything he ever wrote could be better than his journal, comparing his words in those pages to flowers that were freely growing, not transplanted or rearranged:

I do not know but thoughts written down thus in a journal might be printed in the same form with greater advantage—than if the related ones were brought together into separate essays. They are now allied to life—& are seen by the reader not to be far fetched—It is more simple—less artful—I feel that in the other case I should have no proper frame for my sketches. Mere facts & names & dates communicate more than we suspect—Whether the flower looks better in the nosegay—than in the meadow where it grew—& we had to wet our feet to get it! Is the scholastic air any advantage?

To me the answer is clear. Thoreau’s love for nature sings off his journal pages in spring. His winter writing slices right into the heart. His entries, day after day, are testimony to the power of renewal and rebirth—and to the importance of harnessing the human sense of wonder to better understand and protect the Earth. In our age of the Anthropocene, as we distance ourselves from the cyclical rhythms of nature, we are disconnecting from our planet. Thoreau’s journal is a reminder of what is at stake.

A number of writings by Henry David Thoreau appeared in The Atlantic in its early years. In this excerpt, published in the November 2017 issue, Thoreau describes his special love of swamps.