The essay "Civil Disobedience" (1849) - one of the most important texts of political thought - calls on American citizens to refuse to pay the tax imposed on them by the government of James Polk, a government that accepted slavery as a legitimate right and had declared war on Mexico in 1846 with the aim of expanding slavery to the conquered territories. Thoreau formulates here the doctrine of "passive resistance" to power through the expression of disobedience. This, the author says, is dictated by the sense of justice and the awareness of duty. Something similar had been formulated by the romantic poet P.B. Shelley in his poem "The Mask of Anarchy" (1819), a work that deeply influenced Thoreau. For Thoreau, the expression of political disobedience as a dictate of his conscience was nothing but the realization of his individuality. Disobedience becomes the method of defending freedom of conscience and individual rights.

Among the political thinkers who developed the idea of political disobedience in the political conditions of their time, attributing the paternity of the term to Thoreau, the most important were Mahatma Gandhi and Martin Luther King Jr. The first significant author to pay attention to Thoreau's text in the 1866 edition was Leo Tolstoy, who extracts his ideas in "The Kingdom of God Is Within You".