Henry David Thoreau spent almost his entire life in the village of Concord, Massachusetts, where he was born in 1817. After graduating from Harvard College in 1837, he developed a deep friendship with the writer and philosopher Ralph Waldo Emerson, the foremost figure in the Transcendentalist movement. Emerson's emphasis on the cultivation of intuition and experience as keys to personal and social enlightenment profoundly influenced Thoreau. In 1845, Thoreau built a small cabin on a parcel of land Emerson owned near Walden Pond, where he lived for most of two years, seeking a new relationship to nature, society, and his own self. His experiences there are the raw material of his masterpiece, Walden, or Life in the Woods. Although he was first and last a writer and outdoorsman, Thoreau worked as a surveyor and handyman and was an active abolitionist and opponent of war and imperialism. He died in 1862 of tuberculosis. Jedediah Britton-Purdy is the Beinecke Professor at Columbia Law School and a scholar of environmental and constitutional law. His books on environmental themes include After Nature and This Land Is Our Land. He has also written about Henry David Thoreau in venues including The Atlantic, The Nation, and n+1. He grew up in West Virginia and now lives in New York City with his family.