'On the Duty of Civil Disobedience' argues that citizens should not permit their government to overrule their consciences, and that they have a duty to avoid allowing their acquiescence to enable the government to make them the agents of injustice. Thoreau was motivated in part by his disgust with slavery and the Mexican-American War, but the sentiments he expresses here are just as pertinent today as when they were first written. A true American classic.