The Framers of the Constitution knew exactly what kind of government they didn't want. They didn't want the British monarchy, a system of government that centralized so much power in the hands of one man (the King) and one institution (the Parliament) that tyranny became (in the Americans' thinking, at least) the inevitable result. But they also didn't want the Articles of Confederation, the system of government that the newly independent American states had cobbled together in 1781. That system had decentralized power so completely that the feeble national government wasn't able to do much of anything at all. As increasingly serious social and economic problems threatened the young United States over the course of the 1780s, many of America's leading statesmen came to believe that a complete overhaul of the government was needed.
The 55 leaders who met in Philadelphia in 1787 to frame a new Constitution thus had to walk a kind of tightrope. The new government they sought to create couldn't have too much power; that would risk a return of tyranny. But it also couldn't have too little power; that would risk national disintegration.
How could they solve this problem of power? How could they create a new system of government that would allow the new nation to meet its challenges without threatening the cherished freedoms of its people?
Influenced by the great Classical and Enlightenment philosophers of republicanism, but also inspired by their own real-world experiences as British colonial subjects and fledgling American nationalists, they devised a new scheme of government. The Constitution they created in Philadelphia created a new, much more powerful American government… but a government with powers carefully divided among different institutions that could keep each other in check, if necessary.
Four key principles, distinct but mutually reinforcing, are embodied in the Constitution: