This age of reason is supposed to have begun with the publication of ‘the Novum Organum’ by Francis Bacon (1620) and ended with the publication of ‘Critique of Pure Reason’ by Immanuel Kant (1781). On the political scale, it can be assumed to have started with the end of ‘The Thirty Years War’ (1648) and ended with the ‘French Revolution’ (1789).

Immanuel Kant defined the Enlightenment as an age shaped by the Latin motto “Sapere aude” ("Dare to Know"). Unlike Eastern concept of Enlightenment which is spiritual (Moksha, Nirvana) Western Enlightenment is intellectual i.e. development of logic, rationality and objectivity.

This process was closely related to the changes in religion, economy, politics and cultural events in France, Germany and England.

The Scientific Revolution and the Enlightenment opened a path for independent thought, and the fields of mathematics, astronomy, physics, politics, economics, philosophy, and medicine were drastically updated and expanded.

The amount of new knowledge that emerged was staggering. Just as important was the enthusiasm with which people approached the Enlightenment: intellectual salons popped up in France, philosophical discussions were held, and the increasingly literate population read books and passed them around feverishly. The Enlightenment and all of the new knowledge thus permeated nearly every facet of civilized life.

Whether considered from an intellectual, political, or social standpoint, the advancements of the Enlightenment transformed the Western world into an intelligent and self-aware civilization. It is not simply the knowledge attained during the Enlightenment that makes the era so pivotal—it’s also the era’s groundbreaking and tenacious new approaches to investigation, reasoning, and problem solving that make it so important.

Causes

• On the surface, the most apparent cause of the Enlightenment was the Thirty Years’ War. This horribly destructive war, which lasted from 1618 to 1648, compelled German writers to pen harsh criticisms regarding the ideas of nationalism and warfare.

• Second, the Renaissance, with its interest in ancient Greek philosophies, gave rise to secular ideas that helped spawned the scientific revolution of the Enlightenment. This helped discredit the Church's old ideas on the universe and raise the status of humanity and its ability to reason.
• Further, there was the Protestant Reformation. Reformation led to a series of religious wars that ravaged Europe for nearly a century (c.1550-1650). One result of those religious wars was that many people grew tired of religion and socio-economic destruction brought by it. This led to a shift from religion to reason.
• Finally, the rise of towns led to transformation of feudal monarchies into nation states. By the sixteenth century, they were using the doctrine of Divine Right of Kings to undercut the Church's authority in order to elevate their own.

All of these factors converged to undermine the role of blind faith in the Church's authority and helped unleash the age of reason.

·Pre-enlightenment discoveries

The Enlightenment developed through a snowball effect: small advances triggered larger ones, and before Europe and the world knew it, almost two centuries of philosophizing and innovation had ensued. These studies generally began in the fields of earth science and astronomy, as notables such as Johannes Kepler and Galileo Galilei took the old, beloved “truths” of Aristotle and disproved them. Thinkers such as René Descartes and Francis Bacon revised the scientific method, setting the stage for Isaac Newton and his landmark discoveries in physics. From these discoveries emerged a system for observing the world and making testable hypotheses based on those observations. The progressive, rebellious spirit of these scientists would inspire a century’s worth of thinkers.

The Enlightenment in England

The first major Enlightenment figure in England was Thomas Hobbes, who caused great controversy with the release of his provocative treatise Leviathan (1651). In this, he discussed the theory of social contract. He wrote on the best form of governance and assumed that man was innately evil and lived in anarchy. This situation could only be avoided with the creation of a strong and absolute central government through a form of social contract. Peace could only be achieved when man allowed the suppression of personal freedom.

A half century later, John Locke came into the picture, promoting the opposite type of government—a representative government—in his Two Treatises of Government (1690-94). Locke's basic idea was that government, rather than being at the whim of an absolute monarch with no checks on his power, existed merely as a trust to carry out the will of the people and protect their "lives, liberty, and property." If it failed in its duties or acted arbitrarily, the subjects had the right to form a new government, by revolution if necessary.

Locke’s message was closer to the English people’s hearts and minds. In 1688, English Protestants helped overthrow the Catholic king James II and installed the Protestant monarchs William and Mary. In the aftermath of this Glorious Revolution, the English government ratified a new Bill of Rights that granted more personal freedoms.

The Enlightenment in France

France’s Enlightenment came a bit later, in the mid-1700s, but the influence of the Enlightenment ideas was most widespread here because of the efforts of the philosophes. These philosophes, though varying in style and area of particular concern, generally emphasized the power of reason and sought to discover the natural laws governing human society.

The Baron de Montesquieu tackled politics by elaborating upon Locke's work. In his book "The Spirit of the Law" published in 1748, he gave the classic exposition of the idea of separation of powers. Montesquieu’ view is that concentration of legislative, executive and judicial functions either in one single person or a body of persons results in abuse of authority and such an organization becomes tyrannical. He argued that the three organs of government should be so organized that each should be entrusted to different persons and each should perform distinct functions within the sphere of power assigned to it.

Voltaire took a more caustic approach, choosing to incite social and political change by means of satire and criticism. He was famous for his attacks on the established Catholic Church, and his advocacy of freedom of religion, freedom of expression, and separation of church and state.

Denis Diderot, unlike Montesquieu and Voltaire, had no revolutionary aspirations; he was interested merely in collecting as much knowledge as possible for his mammoth Encyclopédie. But his Encyclopédie, which ultimately weighed in at thirty-five volumes, would go a long way to disseminate the Enlightenment knowledge to other countries around the world.

Romanticism

In reaction to the rather empirical philosophies of Voltaire and others, Jean-Jacques Rousseau wrote The Social Contract (1762), a work championing a form of government based on small, direct democracy that directly reflects the general will of the people. For him, humans had to hand over their rights and personal freedom to a sovereign body which decides the form of laws that would protect them as members of society with the same basic rights. All members of society would obey general laws that were agreed upon collectively. The unprecedented intimate perspective that Rousseau provided contributed to a burgeoning Romantic era that would be defined by an emphasis on emotion and instinct, instead of reason. This was the movement which grew as a response to dry logic and objectivity of the Enlightenment.

Skepticism

Another undercurrent that threatened the prevailing principles of the Enlightenment was skepticism. Skeptics questioned whether human society could really be perfected through the use of reason and denied the ability of rational thought to reveal universal truths. Their philosophies revolved around the idea that the perceived world is relative to the beholder and, as such, no one can be sure whether any truths actually exist.

Immanuel Kant, working in Germany during the late eighteenth century, took skepticism to its greatest lengths, arguing that man could truly know neither observed objects nor metaphysical concepts; rather, the experience of such things depends upon the psyche of the observer, thus rendering universal truths impossible. The theories of Kant, along with those of other skeptics such as David Hume, were influential enough to change the nature of European thought and effectively end the Enlightenment.

The End of the Enlightenment

Ultimately, the Enlightenment fell victim to competing ideas from several sources. Romanticism was more appealing to less-educated common folk and pulled them away from the empirical, scientific ideas of earlier Enlightenment philosophers. Similarly, the theories of skepticism came into direct conflict with the reason-based assertions of the Enlightenment and gained a following of their own.

What ultimately and abruptly killed the Enlightenment, however, was the French Revolution. Begun with the best intentions by French citizens inspired by Enlightenment thought, the revolution attempted to implement orderly representative assemblies but quickly degraded into chaos and violence. Many people cited the Enlightenment-induced breakdown of norms as the root cause of the instability and saw the violence as proof that the masses could not be trusted to govern themselves. Nonetheless, the discoveries and theories of the Enlightenment philosophers continued to influence Western society for centuries.