On the Duty of Civil Disobedience is an essay by American author Henry David Thoreau and was first published in 1849 with the title of "Resistance to Civil Government". Thoreau sets for an argument that permit governments to rule or degrade their consciences, otherwise the government forces one to become an agent of injustice. Thoreau was motivated by his opposition to slavery and with the Mexican–American War (1846–1848).