Revolutions in thought—as opposed to those, for example, in politics or science—are in many ways the most influential and far-reaching, because they affect our entire sense of legitimate authority, of the possible and impossible, of right and wrong, and of the potentials of human life.
The intellectual inheritance of the educated world in the 17th century was a fusion of Aristotelian, and other Greek, philosophy and of Christian theology. It was—and is—known as "scholasticism," or, more precisely, as Aristotelian scholasticism. This system dominated the universities and schools of Europe at the time.
Francis Bacon, politician and philosopher, undertook the sizeable tasks of criticizing the Western intellectual inheritance, revising the human quest for knowledge, and transforming the uses of knowledge into power over the forces of nature—upon which humans' suffering, or well-being, was thought to depend.
Astronomy was an eminent science in the 17th century, and much of the challenge to scholasticism began in that field of inquiry. Among the challenges to Aristotelianism was neo-Pythagorean thought, which viewed the universe in terms of mathematics and geometry, not in terms of Aristotelian "qualities," and which saw the Sun as an emblem of God's divinity.
In the first half of the 17th century, Descartes created a coherent philosophical system that became, on the Continent, the major challenge to scholasticism. Descartes sought to demonstrate that humans can establish a criterion of truth and, with it, know with certainty the real nature and the real causes of things.
Hobbes, author of the monumental work of political philosophy known as Leviathan (1651), argued that the world, including the entire realm of human experience, was matter in motion according to fixed, mechanical laws; there was no freedom of the will, and all things were the necessary results of prior causes.
Philosophical skepticism is the belief that we may know nothing with certainty. When used to humble human reason and demonstrate our dependence on religious faith it is termed "fideism"—yet another systematic assault on Aristotelian scholasticism. Blaise Pascal was one of the 17th century's two most influential fideists.
A significant number of critics of Aristotelianism were in communication with each other by the middle of the 17th century. In England, such a group evolved into the Royal Society, which first published the monumental scientific work of Sir Isaac Newton.
The 1687, publication of Newton's Principia Mathematica was not merely a major event in the history of Western science, but a watershed in the history of Western culture. Newton's Principia convinced the majority of its readers that the world was ordered and coherent, and that the human mind, using Baconian inductive methodology and mathematical reasoning, could grasp that order.
John Locke's influence upon the late 17th and early 18th centuries cannot be overestimated; his Essay Concerning Human Understanding (1690) changed the way in which the culture thought about the whole phenomenon of human knowledge.
In Locke's empiricist view, the mind begins as a blank slate on which experience imprints ideas via the senses and via reflection. We cannot know, nor should we speculate about, what is beyond our experience. Because experience is not logically determined, our knowledge of the world is merely probable.
Although obscure to most contemporary readers, the French Protestant fideist Pierre Bayle was one of the most influential authors of his time. His Historical and Critical Dictionary (1697) is intended to expose the arrogance of reason and show that anything but a simple, peaceful faith leads to superstition, intolerance, and cruelty.
This generation of readers and authors increasingly rejects the presumptive authority of the past, increasingly believes induction from data (not deduction from inherited premises) to be the path to truth, and makes a systematic inquiry into experience—now seen as "the book of nature," the heart of natural philosophy, which holds that there are no supernatural beings or causes in the world.
Deism, a widespread religious phenomenon among the educated classes of Europe in the 18th century, embodies belief in a God whose existence and goodness are proven by nature, and disbelief in the Judeo-Christian (or any other) tradition and revelation.
Deism represents the first fundamental challenge to Judeo-Christian theology to emerge strongly within Christian culture itself. Deist and Christian thinkers clash over the most essential theological issues: the source of our knowledge of God, the grounds of religious belief, sin, and more.
If, as the Lockeans believed, knowledge and moral ideas are determined by one's experience, then one's sense of the world must necessarily be relative to one's time, place, personal experience, and physical senses. The Baron de Montesquieu explores this idea, particularly as it touches on questions of law, society, and politics.
Few works had greater impact in popularizing the intellectual revolution of the 17th century, and in inaugurating the debates that would shape the 18th century in France, than Voltaire's Lettres Philosophiques (1734), in which the author celebrates English religious, political, commercial, and intellectual liberty.
Bishop Butler, the preeminent moral theologian of the Church of England, argued that human beings are made for happiness and virtue, and that our nature conduces to both simultaneously. Among those influenced by this revered and pious churchman's views was Thomas Jefferson.
In his posthumously published Dialogues Concerning Natural Religion (1779), the philosopher and skeptic Hume challenged the fundamental premise of natural religion: That we must infer logically from the data of nature a wise, intelligent, good, omnipotent, and providential God.
Candide is Voltaire's most famous and enduring work. On the surface it is a lively satirical novella. It has dark and serious undertones, however, for it marks the author's agonized rejection of the optimistic notion that God would only have created "the best of all possible worlds" and, thus, that all things in the world serve an ultimate good.
In 18th-century France, there emerged a diverse community of thinkers and writers who thought of themselves as new philosophers and whose mission was a critical re-examination of knowledge, authority, and institutions. These were the philosophes of the French Enlightenment.
The view that both individuals and societies should seek happiness led the 18th century to place great weight on the role of the legislator. This, in turn, spawned a great interest in the law and one of the most influential works of the time, Cesare Beccaria's On Crimes and Punishments (1763)—an effort to reform, rationalize, and soften the criminal laws of Europe.
Rousseau, writing in the middle of the 18th century, dissented from prevailing Enlightenment beliefs. He framed a profoundly influential critique, which echoes down to our own day, by arguing that cultural "progress" inevitably leads to moral decadence via the proliferation of artificial needs and inequalities.
The natural, and at times atheistic, world of the philosophe and encyclopédiste Denis Diderot marks the ultimate rejection of the purposeful, qualitative world of Aristotelian scholasticism and begins the debates of the modern age in all of their intensity.