Final answer:
James Madison believed large republics prevent dominance by local interests, provide security against oppressive parties due to diverse interests, and pose greater obstacles to the implementation of selfish majority agendas.
Step-by-step explanation:
The author of the Federalist Papers, particularly James Madison, believed that large republics have several advantages over small ones, and by extension, that the Union (national government) has over individual states (small republics). One fundamental reason is the protection against the tyranny of majority factionalism, where the larger scale of the Union would make it difficult for local interests to dominate at the national level.
Another advantage highlighted by the author is the variety of interests, which can provide greater security against any single party gaining oppressive power. Lastly, the size of the Union itself creates more obstacles to the execution of unjust and selfish majoritarian agendas, further safeguarding the public interest and protecting minority rights.
Madison and other proponents of a larger republic argued that diverse interests and opinions inherent in a vast republic like the United States would prevent the formation of dominant factions that could oppress others. Additionally, a large republic would be able to govern itself more effectively and address the larger common good, rather than the narrow interests that might dominate smaller, more homogeneous populations.