Henry David Thoreau wrote Civil Disobedience. It was first published in 1849 under the title On the Duty of Civil Disobedience (also known as Civil Disobedience or Resistance to Civil Government) and argues that individuals must prioritize conscience over laws when a government endorses injustice, such as slavery or wars. Thoreau’s essay became a foundational text for later nonviolent resistance movements, influencing leaders like Mahatma Gandhi and Martin Luther King Jr.