Ralph Waldo Emerson (May 25, 1803 – April 27, 1882), who went by his middle name Waldo, was an American essayist, lecturer, philosopher, abolitionist, and poet, who led the transcendentalist movement of the mid-19th century. He was seen as a champion of individualism and critical thinking, as well as a prescient critic of the countervailing pressures of society and conformity.