The prophet closes his letter by allusion to a proposed tour of America, adding, that, “if there ever was an object worth the travelling to see, and worthy of the contemplation of a philosopher, it is that in which he may see the beginnings of a great empire at its foundation.” He communicated this purpose also to John Adams, who answered him, that “he would be received respectfully in every part of America, that he had always been considered as friendly to America, and that his writings had been useful to our cause.”[552] Then came another work, first published in 1783, entitled “A Memorial addressed to the Sovereigns of America,” of which he gave the mistaken judgment to a private friend, that it was “the best thing he ever wrote.”[553] Here for the first time American citizens are called “sovereigns.” At the beginning he explains, and indicates the simplicity with which he addresses them:-- “Having presumed to address to the Sovereigns of Europe a Memorial, … permit me now to address this Memorial to you Sovereigns of America. I shall not address you with the court titles of Gothic Europe, nor with those of servile Asia. I will neither address your Sublimity or Majesty, your Grace or Holiness, your Eminence or Highmightiness, your Excellence or Honors. What are titles, where things themselves are known and understood? What title did the Republic of Rome take? The state was known to be sovereign, and the citizens to be free. What could add to this glory? Therefore, United States and Citizens of America, I address you as you are.”[554] Here again are the same constant sympathy with Liberty, the same confidence in our national destinies, and the same aspirations for our prosperity, mingled with warnings against disturbing influences. He exhorts that all our foundations should be “laid in Nature”; that there should be “no contention for, nor acquisition of, unequal domination in men”; and that union should be established on the attractive principle by which all are drawn to a common centre.[555] He fears difficulty in making the line of frontier between us and the British Provinces “a line of peace,” as it ought to be; he is anxious lest something may break out between us and Spain; and he suggests that possibly, “in the cool hours of unimpassioned reflection,” we may learn the danger of our “alliances,”[556]--referring plainly to that original alliance with France which at a later day was the occasion of such trouble. Two other warnings occur. One is against Slavery,[557] which is more memorable, because in an earlier Memorial he enumerates among articles of commerce “African slaves, carried by a circuitous trade in American shipping to the West India markets.”[558] The other warning is thus strongly expressed:--