In 1776, two landmark works appeared. The first of these was Adam Smith's "The Wealth of Nations." The other was the Declaration of Independence. Each was a reflection of the Enlightenment, an intellectual current that swept Europe and America in the 17th and 18th centuries. At its core, the Enlightenment stressed human reason over inherited beliefs. You had to discover truth for yourself, Enlightenment thinkers believed. This basic concept helped spawn a variety of scientific discoveries, a new understanding of religion and two major political revolutions.

The Scientific Revolution

The founding principle of the Enlightenment was rationalism, the belief that truth can only be discovered through logic and reason. French Philosopher Rene Descartes had written that longstanding beliefs should be subjected to rigorous testing and skepticism. This idea served to fuel the scientific revolution of the period. At its forefront was Isaac Newton, whose work demonstrated the mechanisms of gravity. his was but one breakthrough of the era. Others included James Hutton's contributions to geology; James Watt's development of the rotary steam gear; and Benjamin Franklin's experiments with electricity.

Deism: The Religion of the Enlightenment

Skepticism during the Enlightenment was also applied to Christian doctrine. Yet enlightenment thinkers were not true atheists. Rather, most were deists -- they believed in a divinely created universe governed by natural laws. These laws made divine intervention unnecessary. According to the deists, God did not meddle in human affairs. So, most of Christian tradition was merely allegorical, as opposed to factual. These ideas originated in England, but they soon traveled abroad, influencing the likes of Voltaire, Benjamin Franklin and Thomas Jefferson.

New Social Theories

Enlightenment philosophers were also concerned with social issues. The Industrial Revolution was then under way, producing a great deal of poverty and displacement. Intellectuals sought to construct a society that would make people happy. Thomas Hobbes addressed this in his work "Leviathan," which introduced the social contract theory. Hobbes wrote that societies form because people have mutual needs. Yet, society often leaves them impoverished and unhappy. Another theorist, Adam Smith, saw industrialization as the key to mutual prosperity. His economic study, "The Wealth of Nations," called on governments to loosen regulations to allow wealth to circulate more freely in society.

Political Philosophy

The Enlightenment was more than just an intellectual movement, however. It also had a profound effect on 18th century politics, most notably in France and America. Hobbes' "Leviathan" argued that rulers should hold power by the consent of the governed, a theme that was echoed in John Locke's "Second Treatise of Government." Writings like these became the intellectual foundations for both the American and French revolutions. But the French Revolution also undermined the Enlightenment, as it became increasingly totalitarian. The ensuing "Reign of Terror" demonstrated that Enlightenment leaders could not always live up to their own ideals.