He is vain, irritable, and a bad calculator of the force and probable effect of the motives which govern men. This is all the ill which can possibly be said of him. He is as disinterested as the Being who made him. Thomas Jefferson, Letter to James Madison, 1787.
It has been the political careeer of this man to begin with hypocrisy, proceed with arrogance, and finish with contempt. Tom Paine, Open Letter To The Citizens Of The United States, 22 November 1802.
He was terribly open, earnest, and direct, and could not keep his mouth shut.
Theodore Parker, in James B. Peabody ed., John Adams, A biography in his own words.
He can't dance, drink, game, flatter, promise, dress, swear with the gentlemen, and small talk and flirt with the ladies — in short, he has none of the essential arts or ornaments which make up a courtier — there are thousands who with a tenth part of his understanding, and without a spark of his honesty, would distance him infinitely in any court in Europe. Jonathan Sewall, 1787, in Page Smith, John Adams, 1784-1826.