The Enlightenment is the period in the history of western thought and culture, stretching roughly from the mid-decades of the seventeenth century through the eighteenth century, characterized by dramatic revolutions in science, philosophy, society and politics; these revolutions swept away the medieval world-view and ushered in our modern western world. Enlightenment thought culminates historically in the political upheaval of the French Revolution, in which the traditional hierarchical political and social orders (the French monarchy, the privileges of the French nobility, the political power and authority of the Catholic Church) were violently destroyed and replaced by a political and social order informed by the Enlightenment ideals of freedom and equality for all, founded, ostensibly, upon principles of human reason. The Enlightenment begins with the scientific revolution of the sixteenth and seventeenth centuries. The rise of the new science progressively undermines not only the ancient heliocentric conception of the cosmos, but, with it, the entire set of presuppositions that had served to constrain and guide philosophical inquiry. The dramatic success of the new science in explaining the natural world, in accounting for a wide variety of phenomena by appeal to a relatively small number of elegant mathematical formulae, promotes philosophy (in the broad sense of the time, which includes natural science) from a handmaiden of theology, constrained by its purposes and methods, to an independent force with the power and authority to challenge the old and construct the new, in the realms both of theory and practice, on the basis of its own principles. D'Alembert, a leading figure of the French Enlightenment, characterizes his eighteenth century, in the midst of it, as “the century of philosophy par excellence”, because of the tremendous intellectual progress of the age, the advance of the sciences, and the enthusiasm for that progress, but also because of the characteristic expectation of the age that philosophy (in this broad sense) would dramatically improve human life.
The task of characterizing philosophy in (or of) the Enlightenment confronts the obstacle of the wide diversity of Enlightenment thought. The Enlightenment is associated with the French thinkers of the mid-decades of the eighteenth century, the so-called “philosophes”, (Voltaire, Diderot, D'Alembert, Montesquieu, et cetera). The philosophes constitute an informal society of men of letters who collaborate on a loosely defined project of Enlightenment centered around the project of the Encyclopedia. But the Enlightenment has broader boundaries, both geographical and temporal, than this suggests. In addition to the French, there was a very significant Scottish Enlightenment (key figures were Francis Hutcheson, David Hume, Adam Smith, and Thomas Reid) and a very significant German Enlightenment (die Aufklärung, key figures of which include Christian Wolff, Moses Mendelssohn, G.E. Lessing and Immanuel Kant). But all these Enlightenments were but particular nodes or centers in a far-flung and varied intellectual development. Given the variety, Enlightenment philosophy is characterized here in terms of general tendencies of thought, not in terms of specific doctrines or theories.
Only late in the development of the German Enlightenment, when the Enlightenment was near its end, does the movement become self-reflective; the question of “What is Enlightenment?” is debated in pamphlets and journals. In his famous definition of “enlightenment” in his essay “An Answer to the Question: What is Enlightenment?” (1784), which is his contribution to this debate, Immanuel Kant expresses many of the tendencies shared among Enlightenment philosophies of divergent doctrines. Kant defines “enlightenment” as humankind's release from its self-incurred immaturity; “immaturity is the inability to use one's own understanding without the guidance of another.” Enlightenment is the process of undertaking to think for oneself, to employ and rely on one's own intellectual capacities in determining what to believe and how to act. Enlightenment philosophers from across the geographical and temporal spectrum tend to have a great deal of confidence in humanity's intellectual powers, both to achieve systematic knowledge of nature and to serve as an authoritative guide in practical life. This confidence is generally paired with suspicion or hostility toward other forms or carriers of authority (such as tradition, superstition, prejudice, myth and miracles), insofar as these are seen to compete with the authority of reason. Enlightenment philosophy tends to stand in tension with established religion, insofar as the release from self-incurred immaturity in this age, daring to think for oneself, awakening one's intellectual powers, generally requires opposing the role of established religion in directing thought and action. The faith of the Enlightenment – if one may call it that – is that the process of enlightenment, of becoming progressively self-directed in thought and action through the awakening of one's intellectual powers, leads ultimately to a better, more fulfilled human existence.
This entry describes the main tendencies of Enlightenment thought in the following main sections: (1) The True: Science, Epistemology, and Metaphysics in the Enlightenment; (2) The Good: Political Theory, Ethical Theory and Religion in the Enlightenment; (3) The Beautiful: Aesthetics in the Enlightenment. . . .
Read the rest here: http://plato.stanford.edu/entries/enlightenment/.