Contemplations on government in the Western tradition go as far back as Greek philosopher Aristotle. In his discourse On Politics, government for Aristotle is for the well-being of the community and the good-life of its citizens. One of Aristotle's first exercises in identifying the principles of a well-ordered community is to understand the various interests in any community: the one, the few and the many. In Book 3, Chapter VII, Aristotle writes:
Having determined these points, we have next to consider how many forms of government there are, and what they are; and in the first place what are the true forms, for when they are determined the perversions of them will at once be apparent. The words constitution and government have the same meaning, and the government, which is the supreme authority in states, must be in the hands of one, or of a few, or of the many. The true forms of government, therefore, are those in which the one, or the few, or the many, govern with a view to the common interest; but governments which rule with a view to the private interest, whether of the one or of the few, or of the many, are perversions. For the members of a state, if they are truly citizens, ought to participate in its advantages. Of forms of government in which one rules, we call that which regards the common interests, kingship or royalty; that in which more than one, but not many, rule, aristocracy; and it is so called, either because the rulers are the best men, or because they have at heart the best interests of the state and of the citizens. But when the citizens at large administer the state for the common interest, the government is called by the generic name- a constitution. And there is a reason for this use of language. One man or a few may excel in virtue; but as the number increases it becomes more difficult for them to attain perfection in every kind of virtue, though they may in military virtue, for this is found in the masses. Hence in a constitutional government the fighting-men have the supreme power, and those who possess arms are the citizens.
Of the above-mentioned forms, the perversions are as follows: of royalty, tyranny; of aristocracy, oligarchy; of constitutional government, democracy. For tyranny is a kind of monarchy which has in view the interest of the monarch only; oligarchy has in view the interest of the wealthy; democracy, of the needy: none of them the common good of all.
In order to give a society the best chance of stability and peace, Aristotle recommends that the "poor majority" (the many) and the "rich minority" (the few) be given roughly equal amounts of power in the government. Besides the fact that the poor and middle class are more in numbers, the many, collectively in assembly, says Aristotle, are better suited for holding magistrates accountable:
That inferior persons should have authority in greater matters than the good would appear to be a strange thing, yet the election and calling to account of the magistrates is the greatest of all. And these, as I was saying, are functions which in some states are assigned to the people, for the assembly is supreme in all such matters. Yet persons of any age, and having but a small property qualification, sit in the assembly and deliberate and judge, although for the great officers of state, such as treasurers and generals, a high qualification is required. This difficulty may be solved in the same manner as the preceding, and the present practice of democracies may be really defensible. For the power does not reside in the dicast, or senator, or ecclesiast, but in the court, and the senate, and the assembly, of which individual senators, or ecclesiasts, or dicasts, are only parts or members. And for this reason the many may claim to have a higher authority than the few; for the people, and the senate, and the courts consist of many persons, and their property collectively is greater than the property of one or of a few individuals holding great offices. [Book 3, Part XI]
The few have an interest in having representation in the government in order to protect their property and business interests. The segment of society which generates the bulk of the economic activity must have a say in the government of the state. Aristotle astutely observes that constitutions are generally changed or disposed by a large, dissatisfied faction, so preservation of a constitution is generally best accomplished through moderation, education and inclusiveness. 
All men have a claim in a certain sense, as I have already admitted, but all have not an absolute claim. The rich claim because they have a greater share in the land, and land is the common element of the state; also they are generally more trustworthy in contracts. The free claim under the same tide as the noble; for they are nearly akin. For the noble are citizens in a truer sense than the ignoble, and good birth is always valued in a man's own home and country. Another reason is, that those who are sprung from better ancestors are likely to be better men, for nobility is excellence of race. Virtue, too, may be truly said to have a claim, for justice has been acknowledged by us to be a social virtue, and it implies all others. [Book 3, Part XIII]
These principles were fully known by the Founding Fathers and were built into the U.S. Constitution, and John Adams, the nation's second president and an ardent philosopher-thinker, picks up where Aristotle left off. He writes in his tome which defends the Constitution, In Defence of the Constitutions of the United States:
The generation and corruption of governments, which may, in other words, be called the progress and course of human passions in society, are subjects which have engaged the attention of the greatest writers; and whether the essays they have left us were copied from history, or wrought out of their own conjectures and reasonings, they are very much to our purpose, to show the utility and necessity of different orders of men, and of an equilibrium of powers and privileges. They demonstrate the corruptibility of every species of simple government, by which I mean a power without a check, whether in one, a few, or many.
The Founders built upon the concept of the one, the few, and the many that had evolved in Western political theory and had been applied specifically to the governing institutions that had evolved in Great Britain. The one was embodied by the monarch. The few were seated in the House of Lords. And the many were represented in the House of Commons. Each segment of society was present in the government of the British nation, even if not all provinces of that vast empire were so represented.
The writers of the Constitution added further layers of checks and balances to the U.S. system of governance. The president, the one, represents the interests of society at large and has, as Aristotle describes, the royal powers of war. However, these powers of war are checked by the requirement of congressional authorization of any war in which the United States enters.
The Senate, the few, represents the interests of the States and, even more so today since the passage of the Seventeenth Amendment, the interests of the rich minority (to use Aristotle's phrase). The Senate acts as a buffer to the passions of the people through extended debate and the power of individual senators provides insurances that minority interests will at least have a voice. This body also has a say in the the composition of the executive branch through advice and consent, ensuring the few (the States and the wealthy) are adequately confident in the day-to-day administration of the country. However, the Senate must act with the House to pass legislation, ensuring that the rich will not be able to trample the rights of the poor majority.
The House of Representatives, the many, represents the masses of society, ensuring their interests are given voice in the formulation of policy. The constitutional requirement that appropriation bills originate in the House gives the many the power of the purse. However, the Senate must give its approval to all spending measures, ensuring the many will not raid or trample on the property of the wealthy few. And to round out the checks and balances, the presidential veto power means that the House and Senate must act in cooperation with the president to ensure the interests of society at large are considered.
So the one, the few, and the many working together and, indeed, against each other to ensure the proper functioning of the government for the good of all society. Nevertheless, the constitutional design is only as strong as our adherence and dedication to its principles.
SparkNotes summary of Aristotle's On Politics