<P> The Convention agreed on several principles . Most importantly, they agreed that the Convention should go beyond its mandate merely to amend the Articles of Confederation, and instead should produce a new constitution outright . While some delegates thought this illegal, the Articles of Confederation were closer to a treaty between sovereign states than they were to a national constitution, so the genuine legal problems were limited . Another principle they agreed on was that the new government would have all the powers of the Confederation Congress, plus additional powers over the states . Once agreeing on these principles, the Convention voted on the Virginia plan and signaled their approval for it . Once this was done, they began modifying it . </P> <P> Madison's plan operated on several assumptions that were not seriously challenged . During the deliberations, few raised serious objections to the planned bicameral congress, nor the separate executive function, nor the separate judicial function . As English law had typically recognized government as having two separate functions, law making embodied in the legislature, and law executing embodied in the king and his courts, the division of the legislature from the executive and judiciary was a natural and uncontested point . </P> <P> The division of the legislature into an upper and lower house wasn't questioned either, despite the obscure origins of the English House of Lords and its role as the representative of the hereditary nobility . Americans had seldom known any but bicameral legislatures, both in Britain and in most state governments . The main exceptions to this were the dysfunctional Confederation Congress and the unicameral Pennsylvania legislature, which was seen as quickly vacillating between partisan extremes after each election . Experience had convinced the delegates that an upper house was necessary to tame the passions of the lower classes against the interests of wealthy merchants and landowners . Since America had no native hereditary aristocracy, the character of this upper house was designed to protect the interests of this wealthy elite, the "minority of the opulent," against the interests of the lower classes, who constituted the majority of the population . </P> <P> On Thursday, June 7, it was proposed that senators should be chosen directly by the state legislatures, instead of by popular vote, as this method was more likely to preserve the power of the upper classes . Convention delegate Elbridge Gerry of Massachusetts observed that "the great mercantile interest and of stockholders, is not provided for in any mode of election - they will however be better represented if the State legislatures choose the second branch ." The proposal was carried unanimously . </P>

What was the most important challenge facing the constitutional convention