According to Founding Brothers: The Revolutionary Generation, why was the friendship between Jefferson and Adams so central to the development of the United States?
The friendship between Adams and Jefferson was one that transcended political differences. Essentially, Ellis argues that friendship and a sense of mutual respect was critical to the development of the new nation:
...character mattered because the fate of the American experiment with Republican government still required virtuous leaders to survive.
Due to the fragile state of the nation and the experiment, in general, Ellis argues that the friendship and respect that the framers held for one another was the glue that allowed the nation to "congeal." Ellis demonstrates this in his detailing of the friendship between Jefferson and Adams. Theirs was a predicament where political rivalries were intensely present. Jefferson and the Republicans were vociferous critics of the Adams presidency. Yet, after both left office, their friendship resumed through correspondence, something that represents how both essentially held respect for one another outside of politics. This is the type of friendship that showed how the fragile nation was held together because of mutual respect for one another.