After writing the first in the Federalist series Alexander Hamilton turned things over to John Jay, who wrote the next four papers. In No. 2 Jay tries to flip the script on those antifederalists who claimed that the more perfect union envisioned by the Framers was a dangerous innovation. The Framers' desire for a strong union was nothing new, Jay claimed. Instead, the opposition to the new Constitution represented a "new doctrine" that sought "safety and happiness" in "a division of the States into distinct confederacies or sovereignties." It was different from the "strong sense of the value and blessings of union [that] induced the people, at a very early period, to institute a federal government to preserve and perpetuate it." While antifederalists argued that the Articles of Federation were perfectly adequate for that original purpose, but didn't satisfy certain ambitious men, Jay argues that the Articles were a sincere but "greatly deficient and inadequate" attempt, under oppressive wartime conditions, to do what the Constitution would now accomplish. "Publius" rejects a false dichotomy between union and liberty. "Still continuing no less attached to union than enamored of liberty, [federalists] observed the danger which immediately threatened the former and more remotely the latter." They now were convinced that "ample security for both could only be found in a national government more wisely framed."
Jay acknowledges that there had always been resistance to centralized government and suggests that some who supported stronger measures during the Revolution have only now turned against the idea for reasons the author doesn't discuss. In general, resistance can be traced to "the dictates of personal interest," "a mistaken estimate of consequences" or "the undue influence of ancient attachments." Against those tendencies, Jay claims that political union is the natural and desirable consequence of the rise of "one united people" on a continent ideal for commerce. Jay is no multiculturalist on this evidence, nor does he buy the idea that different social or economic arrangements make different cultures. For the most part, however, he's arguing with a straw man here, since I'm not aware of many antifederalists advocating the breakup of the United States. Some did believe, however, that differences among the states or regions of the country had to be respected and defended in a way that implicitly limited central (not to mention popular) power. At this point Jay isn't ready to acknowledge such concerns, but he does remind his readers that the Constitution isn't being forced down anyone's throat. "The plan is only recommended, not imposed," he writes, and time remains for "that sedate and candid consideration which the magnitude and importance of the subject demand." Further reading will show to what extent "Publius" himself was shaped by such consideration.