When writing the Declaration of Independence, members of the Congress outlined reasons for separating from England. When they wrote the Bill of Rights, U.S. leaders were contemplating personal liberties. When writing the Constitution, the primary concern of the authors was to create a system of government that would avoid the problems the United States had encountered with England.
Heavily influencing the framers of the Constitution was the social contract theory as espoused by Jean-Jacques Rousseau and others. Social contract theory states that for a government to be legitimate its creation must be with the consent of the governed. The original Constitution was not perfect in this regard. Because the states controlled elections, they generally limited voting to free white males, and there was typically a requirement that they be landowners. State governors originally appointed members to the Senate rather than have them elected, but the provisions laid out for the election of the House of Representatives and the president ultimately led to greater levels of democracy.
Under British rule, most governments had whatever powers the local governor or the Crown decided they had. One of the most important principles for the framers of the Constitution was limited government. This does not necessarily mean small or weak government, but one with legitimate powers spelled out, along with some restrictions on power. Limited government included the concept of federalism, or the sharing of powers with state and local governments. When ratified, the Bill of Rights served to limit the powers of government further.
Separation of Powers
In the British House of Lords in 1770, William Pitt said, "Unlimited power is apt to corrupt the minds of those who possess it." It is unclear whether America's founding fathers, who declared independence from Britain six years later, ever heard the statement, but they certainly understood the concept. They crafted the U.S. Constitution so that no one individual or body holds too much power. The president, the Senate, the House of Representatives, the courts, state governments and individuals all had their roles to play in the new U.S. power structure.
Checks and Balances
Related to the separation of powers is the concept of checks and balances. The framers of the Constitution not only had limited powers, they had the ability to block the powers of others. The president, for example, commands the troops but only Congress can declare war. The Congress passes laws, but the president can veto them. The Congress, in turn, can override the presidential veto if support is strong enough. The Supreme Court can rule a law unconstitutional. Impartial "judicial review" was another important concept to the framers. The people, of course, can remove representatives from office in regular elections if there is no popular support for their actions.