Henry David Thoreau was a 19th century American writer, philosopher and naturalist. He graduated from Harvard but was fired from teaching for refusing to discipline his students physically. In 1845, he built a cabin at Walden Pond where he lived in isolation for over two years, during which he wrote his famous book Walden. The book detailed his experiment in simple living and self-sufficiency at the pond. He is also known for his essay "Civil Disobedience" where he advocated for individual resistance to an unjust state.