In 1846 the United States invaded Mexico. At the same time, the controversy over slavery, which would finally boil over in 1861 with the start of the Civil War, was already intense. Out of this moment came, among other things, Henry David Thoreau’s essay, “On Civil Disobedience,” which would inspire both Mahatma Gandhi and Martin Luther King, Jr.

Thoreau quotes “Paley, a common authority with many on moral questions,” who

resolves all civil obligation into expediency; and he proceeds to say that “so long as the interest of the whole society requires it, that is, so long as the established government cannot be resisted or changed without public inconveniency, it is the will of God. . .that the established government be obeyed . . . .”

Thoreau objects to this mode of ethical reasoning in vivid terms:

But Paley appears never to have contemplated those cases to which the rule of expediency does not apply, in which a people, as well as an individual, must do justice, cost what it may. If I have unjustly wrested a plank from a drowning man, I must restore it to him though I drown myself. This, according to Paley, would be inconvenient. But he that would save his life, in such a case, shall lose it. This people must cease to hold slaves, and to make war on Mexico, though it cost them their existence as a people.