in support of this was that most of the states were focused on one industry—to generalize, commerce and shipping in the northern states and plantation farming in the southern. The Anti-Federalist belief that the wide disparity in the economic interests of the various states would lead to controversy was perhaps realized in the American Civil War, which some scholars attribute to this disparity. Madison himself, in a letter to Thomas Jefferson, noted that differing economic interests had created dispute, even when the Constitution was being written. At the convention, he particularly identified the distinction between the northern and southern states as a "line of discrimination" that formed "the real difference of interests". The discussion of the ideal size for the republic was not limited to the options of individual states or encompassing union. In a letter to Richard Price, Benjamin Rush noted that "Some of our enlightened men who begin to despair of a more complete union of the States in Congress have secretly proposed an Eastern, Middle, and Southern Confederacy, to be united by an alliance offensive and defensive". In making their arguments, the Anti-Federalists appealed to both historical and theoretic evidence. On the theoretical side, they leaned heavily on the work of Charles de Secondat, Baron de Montesquieu. The Anti-Federalists Brutus and Cato both quoted Montesquieu on the issue of the ideal size of a republic, citing his statement in The Spirit of the Laws that: It is natural to a republic to have only a small territory, otherwise it cannot long subsist. In a large republic there are men of large fortunes, and consequently of less moderation; there are trusts too great to be placed in any single subject; he has interest of his own; he soon begins to think that he may be happy, great and glorious, by oppressing his fellow citizens; and that he may raise himself to grandeur on the ruins of his country. In a large republic, the public good is sacrificed to a thousand views; it is subordinate to exceptions, and depends on accidents. In a small one, the interest of the public is easier perceived, better understood, and more within the reach of every citizen; abuses are of less extent, and of course are less protected. Greece and Rome were looked to as model republics throughout this debate, and authors on both sides took Roman pseudonyms. Brutus points out that the