With publication of Federalist Paper #14, Objections to the Proposed Constitution From Extent of Territory Answered, James Madison brings the argument of union vs disunion to a close. He explains clearly the difference between a democracy and a republic.
To the critics who claim that a republic must be confined to a small territory, Madison writes that they confuse a republic with a democracy. The difference, according to Madison, is that in a democracy the people meet and exercise the government in person, whereas in a republic the people govern the country through their elected representatives. Because a republic has representatives, it can extend over a large region.
Madison makes an appeal to exceptionalism – the unique sprit of Americans to try something new even though there is no historic precedent for such an ambitious endeavor. He appeals to the patriotism of citizens to create something for all mankind to follow.
Go to the GrAdeSaver Summary of Federalist #14