Ralph Waldo Emerson (1803-1882) was a prominent lecturer, poet, and essayist. He was a mentor and friend to Henry David Thoreau. Known as the "Sage of Concord" for his place of residence in Massachusetts, Emerson was a major literary figure and an important spokesman for transcendentalist philosophy, the New England movement that flourished until the Civil War, primarily among intellectuals. Transcendentalism was in part a reaction against Unitarian Church orthodoxy.
Emerson proved prophetic when he wrote that America's swallowing up of over half of Mexico would be analogous to a man who swallows arsenic, "which brings him down in turn. Mexico will poison us."_CITATION_UUID_66934F6DA1FB4E81B9CF3D07961D64B4_ He was openly against the war and thought that the spectacle of it all had sucked the country into a dangerous state of delirium.