The American Revolution inaugurated the first government in the world that was based on the principle that sovereignty and rights are in the people and not in the king or the ruling class.
Jefferson—who was a man of the Enlightenment, and by no means an orthodox Christian—nevertheless locates the source of equality and rights in a single source: the Creator. Why does he not locate the doctrine of equality in the people, in the consent of the governed? Because never have “all men” or all people ever given their consent to such a proposition. Moreover, even if they did, all people don’t become equal—any more than they become tall or intelligent or morally good—by mutual or common agreement!
In the old case the king granted limited authority and power to the people; in America, the people grant limited authority and power to their rulers.
So the government that controls the people is, through majority rule, selected by the people. But who controls the government? The American answer to this question is: the Constitution.
The American Founders, however, adopted a Constitution which is a “higher law,” a law that trumps even majority rule. Why is such a law necessary? When governments are given power through a democratic process, why do they need to be restricted and over-ridden by a higher law? The reason is that the American Founders recognized the limits of majority rule.
Another way to put it is that the majority must not use its power to trample on minority rights. The Founders were very concerned about this. What if the majority decides, for instance, to confiscate the property of the minority? The Founders insisted that “tyranny of the majority” is just as dangerous as having a one-man tyrant. In some ways, it’s more dangerous. It’s bad enough to be oppressed by one man—even worse to be oppressed by the bulk of your fellow citizens.
Consequently the American Founders implemented multiple mechanisms for limiting the power of the central government—even an elected government—and for ensuring that this government did not become oppressive to all or even some of its citizens. The Constitution is a charter for limited government. Basically it says that the federal government can do this, this, and this. And beyond this, the federal government has no power to act.
others wanted it in writing that government could not abridge certain fundamental rights, and so the Bill of Rights was adopted in the form of amendments to the Constitution.
In addition to limiting the size and power of the federal government, the Founders divided power between the federal government on the one hand, and states and local governments on the other. This principle is called “federalism.” They also divided the federal government between a legislature, executive, and judiciary, which we know as a “separation of powers” and they instituted a system of “checks and balances” giving different branches of government (say the House and the Senate, or the president and the Congress, or Congress and the courts) authority to exercise competing authority on the same issue.