When Henry David Thoreau died at age 44, he remained an enigma even to those who knew him best. Was he a crank or a prophet? Had he frittered away his time and talents, or had he crafted an exemplary life and enduring art?

Ralph Waldo Emerson, Thoreau’s most devoted mentor and patron, delivered a eulogy at the funeral that mixed praise with bewilderment. Why was Thoreau so contrary, Emerson wondered, so opposed to almost every social convention, so stern with adults yet playful with children, so much more eager to lead a huckleberry party than to harness his genius to some “great enterprise”? Despite misgivings about Thoreau’s prickly character, Emerson admired “the superiority which shone in his simple and hidden life.” To be in Thoreau’s company, Emerson declared, made one curious “to know more deeply the secrets of his mind.”

Since that funeral oration in 1862, friends of Thoreau, biographers, literary critics and readers have been seeking to know “the secrets of his mind.” Michael Sims, author of several books on our ways of imagining nature, introduces his study as an effort to uncover the man behind the myth. Between an opening sketch of Thoreau’s childhood and a closing sketch of the last 15 years of his life, Sims focuses on the period between his matriculation at Harvard in 1833 and his moving out of the Walden Pond cabin in 1847.

His principal sources, in addition to Thoreau’s voluminous journal, are the journals, letters and memoirs of people who knew the young Henry — from prominent figures such as Emerson, Nathaniel Hawthorne and Bronson Alcott (father of the more famous Louisa May), to Ellery Channing, a walking companion, and 17-year-old Ellen Sewall, who declined his proposal of marriage. Because the same sources have been mined by biographers — most notably by Walter Harding in “The Days of Henry Thoreau” and Robert D. Richardson Jr. in “Henry Thoreau: A Life of the Mind” — Sims struggles at times to find something fresh to say.

Nonetheless, while narrating familiar episodes, Sims offers intriguing sidelights and memorable details. He tells us, for example, that during Thoreau’s time at Harvard, each student was provided with a cannonball, which could be heated in the fireplace and then used to radiate warmth on chilly nights. Soon after graduation, Thoreau secured a position in a local grammar school, but when he was reprimanded for not thrashing his students, he whipped a number of them arbitrarily, a violent move that surprised those who knew him, according to Sims, and he promptly resigned rather than continue beating children.

You will read here how Thoreau’s beloved older brother, John, was the first to propose to Ellen Sewall, only to be vetoed by her parents, and how Thoreau’s proposal was vetoed in turn. You will read of the brothers’ expedition in their leaky, homemade boat down the Concord and Merrimack Rivers, which provided the narrative thread for Thoreau’s first book. And you will read of John’s agonizing death from lockjaw after cutting his finger while shaving, and of Thoreau’s subsequent profound depression, during which he exhibited all the symptoms of John’s fatal disease.

Likewise, Sims provides engaging accounts of Thoreau’s fascination with Indians, his embrace of abolitionism (under the influence of his mother and sisters), his contributions to the family pencil business, his ungainly ice-skating, his devotion to natural history and his delight in the company of children. In recounting how Thoreau refused to pay the poll tax out of opposition to a government that condoned slavery and waged imperialist wars, a refusal that led to a night in jail and a renowned essay on “Civil Disobedience,” Sims points out that Thoreau willingly paid taxes for schools and roads.

If you know anything at all about Thoreau, you know that he spent some time — two years, two months and two days, to be exact — living in a cabin beside Walden Pond. But you might not know, as Sims informs us, that he left the bark on the rafters, used a three-inch looking-glass for shaving, opened the cabin to a meeting of the Concord Female Anti-Slavery Society and entertained a resident field mouse by playing the flute.

Through such details, Sims helps us to see Thoreau as a colorful, crotchety human being. What Sims makes no attempt to explain is the grand achievement proclaimed by Emerson in his eulogy: “Mr. Thoreau dedicated his genius with such entire love to the fields, hills, and waters of his native town, that he made them known and interesting to all reading Americans, and to people over the sea.” To discover why his work still inspires countless readers a century and a half after his death, you will have to read Thoreau himself.

Sanders is the author of “Earth Works: New & Selected Essays.” His novel, “Divine Animal,” has just been released.


A Young Man’s Unlikely Path to Walden Pond

By Michael Sims

Bloomsbury. 372 pp. $27