Thomas Jefferson, April 28, 1793 letter to George Washington

"...The Law of nations, by which this question is to be determined, is composed of three branches,

1. The Moral law of our nature.

2. The Usages of nations.

3. Their special Conventions.

"The first of these only, concerns this question, that is to say the Moral law to which Man has been subjected by his creator, & of which his feelings, or Conscience as it is sometimes called, are the evidence with which his creator has furnished him. The Moral duties which exist between individual and individual in a state of nature, accompany them into a state of society & the aggregate of the duties of all the individuals composing the society constitutes the duties of that society towards any other; so that between society & society the same moral duties exist as did between the individuals composing them while in an unassociated state, their maker not having released them from those duties on their forming themselves into a nation. Compacts then between nation & nation are obligatory on them by the same moral law which obliges individuals to observe their compacts. There are circumstances however which sometimes excuse the non-performance of contracts between man & man: so are there also between nation & nation. When performance, for instance, becomes impossible, non-performance is not immoral. So if performance becomes self-destructive to the party, the law of self-preservation overrules the laws of obligation to others. For the reality of these principles I appeal to the true fountains of evidence, the head & heart of every rational & honest man. It is there Nature has written her moral laws, & where every man may read them for himself. He will never read there the permission to annul his obligations for a time, or for ever, whenever they become "dangerous, useless, or disagreeable." Certainly not when merely useless or disagreeable, as seems to be said in an authority which has been quoted, Vattel, 2. 197, and tho he may under certain degrees of danger, yet the danger must be imminent, & the degree great. Of these, it is true, that nations are to be judges for themselves, since no one nation has a right to sit in judgment over another. But the tribunal of our consciences remains, & that also of the opinion of the world. These will revise the sentence we pass in our own case, & as we respect these, we must see that in judging ourselves we have honestly done the part of impartial & vigorous judges...."

- Thomas Jefferson, April 28, 1793 letter to George Washington. [The Works of Thomas Jefferson in Twelve Volumes. Federal Edition. Collected and Edited by Paul Leicester Ford.]