What a stupendous, what an incomprehensible machine is man! who can endure toil, famine, stripes, imprisonment & death itself in vindication of his own liberty, and the next moment be deaf to all those motives whose power supported him thro’ his trial, and inflict on his fellow men a bondage, one hour of which is fraught with more misery than ages of that which he rose in rebellion to oppose.

Thomas Jefferson (1743-1826) American political philosopher, polymath, statesman, US President (1801-09)

Letter to Jean Nicholas Démeunier (22 Jun 1786)
    (Source)

This was part of a response to a draft article on the United States ("Essai sur les États-Unis") being put together for the Encyclopédie Méthodique which Démeunier had passed by Jefferson for comment. Jefferson requested changes on a number of items, including a passage on a new Virginia slave law and the failure of some of the delegates to propose an amendment for the gradual emancipation of slaves (Jefferson had not attended the legislative session, being in France). This quotation appeared toward the end of that proposed revision.

In the end, Démeunier provided this French translation in his article:

L’homme est un être bien étonnant et bien incompréhensible! pour défendre sa liberté, il souffre la fatigue, la faim, les coups de fouet, la prison et la mort, et le moment d’après les nobles sentimens qui l’ont soutenu dans de cruelles épreuves, ne font plus d’impression sur lui, et il impose à d’autres hommes une servitude qui, dans la durée d’une heure, produit plus de peines et de douleur, que l’assujettissement contre lequel il a pris les armes, n’en eût produit dans des siecles.