[John Adams] diary, of course, is even more revealing of his feelings. Both his letters to [his wife] Abigail and his diary tell us what he really thinks about people and events.

After [Tomas] Jefferson's defeat of [John] Adams in the presidential election of 1800, they didn't communicate with one another for more than a decade.

[John] Adams identified himself with the political theories of [James] Harrington, [John] Locke, and [Charles-Louis] Montesquieu, whose ideas of constitutionalism, he believed, were applicable to all peoples everywhere; they were his contribution to what he called "the divine science of politics."

Again and again [Tomas] Jefferson deftly sidesteps many of [John] Adams's often provocative remarks. They both felt the correspondence, which was written for posterity, was too important to risk by being too candid with one another.

A mutual friend, Benjamin Rush, brought [Tomas Jefferson and John Adams] together in 1812, and they went on to exchange letters for the rest of their lives. But in their correspondence they tended to avoid the most controversial issues, such as slavery.

[John Adams] always felt that his contribution to bringing about independence went unappreciated, especially after the 1790s when [Tomas] Jefferson began to be lauded as the "author" of the Declaration of Independence.

I think [John Adams] developed a much deeper suspicion of France and the other European powers than he had earlier. He lost much if not all of the utopian thinking about international politics and diplomacy expressed in his Model Treaty of 1776 and became much more cynical about the world.