John Locke is considered the "father of liberalism" and was one of the most important thinkers of the Enlightenment period. Locke's ideas formed the basis for social contract theory, a philosophy developed later by other writers in Europe.

In his Second Treatise of Government, Locke identifies the basis of a legitimate government. He argues that a ruler gains "true," or rightful authority, only through the consent of the governed. He also argues that the duty of any government is to protect the natural rights of its citizens, which include life, liberty, and the possession of property. Locke’s ideas are reflected in both the Declaration of Independence and the U.S. Constitution.

Charles-Louis Montesquieu was a French Enlightenment philosopher who lived during the 17th and 18th centuries. His writings and his political ideas were widely read by American colonists and had a major influence on the drafting of the U.S. Constitution. The Founding Fathers directly adopted Montesquieu's ideas about the separation of powers. This led them to create checks and balances among the legislative, executive, and judicial branches of the new government created by the Constitution.

Montesquieu based his thinking on the republican government of the ancient Romans and on the parliamentary monarchy of Britain. These governments, he argued, prevented both the concentration of power in one person's hands and the infringement upon individual liberties that often occurs under dictatorial governments.

Many of Montesquieu’s central ideas came from the writings of John Locke. The theories of both men regarding individual rights to life, liberty, prosperity, and property are still considered critical to the success of electoral democracies.