If a man does not keep peace with his companions,
perhaps it is because he hears a different drummer.
Let him step to the music he hears,
however measured or far away.
The essay Civil Disobedience (1849) grew out of his overnight stay in prison as a result of his refusal to pay a tax supporting the Mexican War. This story is told in the play The Night Thoreau Spent in Jail. This concept of resistance was later used by Mahatma Ghandi in India to throw off British rule and later by Martin Luther King in his Civil Rights protests.

Less commonly known, Thoreau was also a naturalist emphasizing the dynamic ecology of the natural world.