Ralph Waldo Emerson (May 25, 1803 – April 27, 1882), who went by his middle name Waldo, was an American essayist, lecturer, philosopher, and poet who led the transcendentalist movement of the mid-19th century. He was seen as a champion of individualism and a prescient critic of the countervailing pressures of society, and he disseminated his thoughts through dozens of published essays and more than 1,500 public lectures across the United States.
Emerson gradually moved away from the religious and social beliefs of his contemporaries, formulating and expressing the philosophy of transcendentalism in his 1836 essay "Nature". Following this work, he gave a speech entitled "The American Scholar" in 1837, which Oliver Wendell Holmes Sr. considered to be America's "intellectual Declaration of Independence."
He remains among the linchpins of the American romantic movement, and his work has greatly influenced the thinkers, writers and poets that followed him. "In all my lectures," he wrote, "I have taught one doctrine, namely, the infinitude of the private man." Emerson is also well known as a mentor and friend of Henry David Thoreau, a fellow transcendentalist.