How is Jefferson influenced by Enlightenment thinking?

Thomas Jefferson was influenced by Enlightenment figures in many different ways. Jefferson dedicated much of his intellectual life to studying famous philosophers, scholars, and scientists from the Enlightenment era, men like John Locke, Sir Isaac Newton, and Montesquieu. As a result, many Enlightenment “ideas” made their way into Jefferson’s writings (and later, his political policies), most notably the Declaration of Independence.
One central political idea of the Enlightenment was the belief that individuals were entitled to certain guarantees from their government, like life, liberty, and property. Moreover, many Enlightenment intellectuals believed that government was obligated to protect their citizens’ personal and political rights. (For example, governments were supposed to simultaneously protect their citizens’ right to own property, while also protecting their right to free speech.)
Jefferson infused his most famous political writing—the Declaration of Independence—with many Enlightenment ideas, most famously the idea that all Americans were entitled to the rights of “life, liberty, and the pursuit of happiness.” However, Jefferson justified the writing of the Declaration from the work of Enlightenment figure John Locke and Locke’s “social contract” theory. Under the social contract, citizens were obliged to support and respect their government as long as their government protected their individual rights and liberties. If the government failed in doing so, then the citizens had the right to rebel against their government and establish a better system for themselves. Jefferson mentions this in the Declaration, arguing that Great Britain had abused the rights of its American subjects and the colonies were therefore justified in declaring their independence.
While influenced heavily by the Enlightenment and its key intellectual leaders, Jefferson and the Declaration should be considered an equal part of that era. Enlightenment ideas would continue to shape other movements of the period, including the French Revolution.
For more information, see: Meacham, Jon. Thomas Jefferson: The Art of Power. New York, NY: Random House Trade Paperbacks, 2013.