In one of his last letters before his death, Jefferson wrote that the "principles of the Declaration were found in the — elementary books of public right, as Aristotle, Cicero, Locke & Sidney." Considered the first political scientist, Aristotle — a disciple of Plato — examined different types of governments, their strengths and weaknesses, and the possibility of combining stability and justice.

The second of Jefferson's ancient sources, Cicero was a Roman statesman, orator, and philosopher. This volume attempts to clarify how a large, diverse nation can remain true to republican principles.

Locke was a 17^th-century English political philosopher whose books, along with the Bible, were among those most cited by the Founders. He was a pioneer theorist of limited government and religious tolerance. His most important works are his Second Treatise of Government and his Letter on Toleration.

The founders recognized Sidney's Discourses as the classic defense of republicanism and popular government. Sidney was a martyr of the anti-monarchical party opposing James II. He is part of a tradition of English defenders of republicanism against established or state-sponsored religion.

This very influential collection of short biographies paired famous generals, statesmen, and political founders in the Greek and Roman worlds. The American Founders regarded Plutarch as a rich source for understanding human nature, political motivation, virtue, and the desire for honor and fame.

Montesquieu argues for the connection between character and politics. His description of the separation of powers made him a crucial source for the Founders.

Smith defends the moral and political advantages of free market economics.

Thucydides' history of the war between the Peloponnesians and the Athenians was often cited by the Founders, and influenced their understanding of human nature and politics.