The Enlightenment was as much a reaction to the horror of the Thirty Years War and the English Civil War as it was a natural follow on the Reconnaissance. It brought a new sense of scientific openness and concern for the human condition to Europe and set the stage for the founding of the American Republic, the only state formed on its core principles.
The Enlightenment marked a clear delineation between societies dominated by religious and those governed by civil administration and the concept of "rationalism". For part of Europe and the Americas, it also meant a rise in humanism and scientific inquiry unfettered by the bounds of religion. The rise of scientific inquiry gave rise to the scientific method. It focused on finding natural causes for events rather than supernatural or religious causes.
The Enlightenment had two driving premises: rationalism and liberty. Rationalism drove the quest to free the mind and seek out cause and effect relationships and to inquire into the cosmos. Liberty sought to free the individual and recognize natural rights that came not from governments, but simply as a state of nature. These two were related as the Enlightenment sought to define the relationship between the individual and the cosmos in ways that did not require supernatural beliefs, but rather provable and reproducable causal relationships.
These premises set the stage for two critical conflicts:
Unchecked liberty, however, also lead to potential excess and the charge of being a "libertine". The word "libertine" first came in use to a person freed from slavery. As the Reformation took root, it also took on a new meaning: a religious freethinker. This stems naturally from the concept a ""freedman". The religious freethinker was freed from the constraints of religious dogma. As many of these "freedman" began to act in ways that specifically pleased them regardless of social mores and constraints, it also took on the meaning that most people associate with the word today: a person of loose moral character, especially about sex.
This linkage had two key consequences for the Enlightenment and fostered the conflicts listed above:
The groups that felt threatened by the Enlightent used these consequences to rally support for a "Counter Enlightenment" that preserved the existing structures of the old order in Europe and started to weaken the awareness of the Enlightenment and its key tenets in the fledgling United States. Europe had to wait until the revolutions of 1848 to re-awaken the flame of liberty and the desolation of World War I to break up some of its hegemonic empires.
The most significant cultural movements to counter the Enlightenment was Romanticism, which sought to restore a sense of mystery to the cosmos and Nationalism, which sought to raise the importance of the state and cement the individual's identity to the state.
These movements had an impact even in the United States, the only state founded upon the principles of the Enlightenment. As the state grew more powerful in response to key events such as the American Civil War, American's neo imperialism surrounding the Spanish American War, the consolidation of federal power with Constitutional Amendments in 1913, the further consolidation of power with the New Deal, the rise of American power after World War II, and the rise of the welfare state with the Great Society, the American concept of liberty and the relationship between the individual and the state changed dramatically.
Today, few Americans even know about the Enlightenment, let alone understand its core tenets and the underlying philosophy and philosophers that framed it.