Federalist Papers

Why do the authors of the Federalist Papers assert that a republic or confederation of states is an ineffective way to govern the United States? (see Federalist 9 and 10 specifically)

What do they suggest in place of the system established by the Articles of the Confederation?

What techniques of persuasion are at work in the Papers? (for example, fear of disintegration,
Providence, hope of economic prosperity, etc)