An Abolitionist, Henry David Thoreau was a true man of principle because he acted upon his beliefs. For, he refused to pay a poll tax in his state because the monies gathered from this tax went toward funding that against which he objected. When the Mexican War began in 1846, he protested against it as an act of aggression that was designed to gain new slave territories for the United States. Consequently, he refused to pay the tax that supported this war.
After he was arrested for having refused to pay the taxes, Thoreau went to jail rather than pay the fine and taxes. He wrote,
Must the citizen ever for a moment, or in the least degree, resign his conscience to the legislator? Why has every man a conscience, then? I think that we should be men first, and subjects afterward. it is not desirable to cultivate a respect for the law, so much as for the right.
Thoreau's action of civil disobedience gave birth to the act later termed "passive resistance" or "non-violent protest," not to mention "civil disobedience" itself. Such non-violent protest was employed in India as Mahatma Gandhi led his people towards freedom from the colonial government of England. In the twentieth century, civil disobedience was exercised by the Civl Rights protestors; in fact, Dr. Martin Luther King even quotes Thoreau in his famous "Letter from a Birmingham Jail" after his arrest.
When a law is unjust, Thoreau, Gandhi, and King all felt that a man must protest these laws through non-violent resistance, acts of civil disobedience because "citizens must never surrender their conscience to the legislators."