Which document outlines the foundational principles of American democracy?

The Constitution of the United States serves as the foundational document outlining the principles of American democracy. It establishes the framework for the government, detailing the separation of powers among the legislative, executive, and judicial branches. Moreover, it enumerates the rights of citizens and the responsibilities of the government, thereby underscoring the principles of democracy such as checks and balances, representative government, and the rule of law.

The other documents mentioned play important roles in American history and governance but serve different purposes. The Federalist Papers, for example, were a series of essays advocating for the ratification of the Constitution, providing insight into the framers' intentions. The Articles of Confederation were the first attempt at governance following independence but proved inadequate, leading to the creation of the Constitution. The Declaration of Independence expresses the philosophical foundations of freedom and individual rights but does not provide the structure or mechanisms of government that support American democracy in the way the Constitution does.