The very complication of the business, by introducing a necessity of the concurrence of so many different bodies, would of itself afford a solid objection. . . . [a] source of so great inconvenience and expense as alone ought to condemn the project.- Alexander Hamilton, Federalist 75
The consensus among critics of the Constitution is that many of the ordeals we are confronted with in our society are directly traceable to a constitutional structure that was designed by the Framers to be permanently divided against itself. The structure they instituted has resulted in paralysis and a lack of governmental accountability, and a concomitant inability to prevent social breakdown.
This was not completely the fault of the Framers; after all, they were not designing a Constitution for the 21st Century. They were simply trying to create a New Constitution for the 18th Century, since experience with the previous constitution (the Articles of Confederation) revealed fatal flaws in that document. Consequently, our Framers met in the Federal Convention of 1787 to draft a New Constitution for the United States of America. This 1787 Constitution was formed under several new theories of Government - most notably the Separation of Powers Principle and the need for a Bicameral Legislature - which Hamilton enumerated in Federalist 9:
The regular distribution of power into distinct departments - the introduction of legislative balances and checks - the institution of courts composed of judges holding their offices during good behavior - the representation of the people in the legislature by deputies of their own election: these are wholly new discoveries, or have made their principal progress towards perfection in modern times. They are means, and powerful means, by which the excellences of republican government may be retained and its imperfections lessened or avoided.
In one of the most famous essays in The Federalist, Federalist 51, Madison described how the principle of Government divided against itself into three separate Branches would maintain the integrity of the individual Branches:
To what expedient, then, shall we finally resort for maintaining in practice the necessary partition of power among the several departments, as laid down in the Constitution? . . . [T]he defect must be supplied, by so contriving the interior structure of the government as that its several constituent parts may, by their mutual relations, be the means of keeping each other in their proper places. . . .
[E]ach department should have a will of its own; and, consequently, should be so constituted that the members of each should have as little agency as possible in the appointment of the members of the others.
A system of Checks and Balances was instituted, which allowed each one of the three Branches of Government, the Legislative (the lawmakers), the Executive (the enforcers of the law), and the Judicial (the determinants of whether or not a law was broken) to restrict in some manner the actions of the other:
[T]he great security against a gradual concentration of the several powers in the same department, consists in giving to those who administer each department the necessary constitutional means and personal motives to resist encroachments of the others. The provision for defence must in this, as in all other cases, be made commensurate to the danger of attack. Ambition must be made to counteract ambition. The interest of the man must be connected with the constitutional rights of the place.
The Framers knew that it was not enough to rely on politicians to "do the right thing" and maintain the integrity of the Branches themselves; even the power of voting politicians out of office was not enough to secure the constitutional structure. Thus, the Constitution would contain within itself the means of its self-preservation. Under the Separation of Powers Principle as instituted in the Constitution, each Branch would confront the other. Government was weakened under the divide et impera [divide and rule] maxim referred to by Hamilton in Federalist 7:
This policy of supplying, by opposite and rival interests, the defect of better motives, might be traced through the whole system of human affairs, private as well as public. We see it particularly displayed in all the subordinate distributions of power, where the constant aim is to divide and arrange the several offices in such a manner as that each may be a check on the other; that the private interest of every individual may be a centinel over the public rights. 
Since the nature of the powers were different, the nature of the checks also had to be different. Because the Legislative Branch was seen as the most powerful, it was subdivided (again, divide et impera) into a House of Representatives and Senate.
[I]t is not possible to give to each department an equal power of self defence. In republican government, the legislative authority necessarily predominates. The remedy for this inconveniency is to divide the legislature into different branches; and to render them, by different modes of election and different principles of action, as little connected with each other as the nature of their common functions and their common dependence on the society will admit.
As if this evisceration of Legislative power wasn't enough to secure the objective of the Framers, the Executive Branch was given what was actually a Legislative power, an overrulable veto, to stop "encroachments" by the Legislative Branch. Thus, the form of Government given to us by the Framers in 1787 was a Legislative Branch divided into two separate Branches, with that Branch checked by a President with veto power, and a Supreme Court with the power (as it subsequently developed) to determine laws unconstitutional - a Government permanently divided against itself. This division sought to preserve the integrity of the Branches, but at a heavy and unavoidable cost: delay in the face of a necessity for action.
END PART 5: TO BE CONTINUED
 Federalist 75, pp. 381-2 (Hamilton).
 Federalist 9, p. 38 (Hamilton).
 Federalist 51, p. 261 (Madison).
 Federalist 51, p. 262 (Madison).
 Federalist 51, p. 263 (Madison).
 Federalist 51, p. 263 (Madison).