Ralph Waldo Emerson was the leading proponent of the Transcendentalist movement of the mid-nineteenth century. He was ordained as a Unitarian minister at Harvard Divinity School but served for only three years before developing his own spiritual philosophy based on individualism and intuition. His essay Nature is arguably his best-known work and was both groundbreaking and highly controversial when it was first published. Emerson also wrote poetry and lectured widely across the US.