For two thousand years rationalism had beckoned from the heights, and Western Civilization had ignored the call. Sure, the thinkers might worship rationalism, and logical thinking had slowly penetrated into the pores of Western thinking, but as a whole, Western Civilization just after the Reformation regarded rationalism as the preserve of scholars, not something to embrace. Religious excess broke the dam.
The wars of religion had started as early as the 1520's, and continued for 130 years. Everywhere they were marked by atrocity. The Catholic Church burned heretics; the Spanish Catholic armies murdered woman and children in the Netherlands; the French massacred the Huguenots; and the English maintained a steady flow of religious executions.
But it was the Thirty Years' War that shocked Christendom into sense. The formula for peace that had been worked out at the Diet of Worms, allowing each petty prince in Germany to establish the state religion for that principality, had created a confessional checkerboard across Germany. And when war broke out, armies marched across Germany, burning and killing all those who did not share their religion. The result was the catastrophic devastation of Germany. Not only were millions of civilians horribly murdered; the entire infrastructure was torn down. Farms were burnt, villages destroyed, towns and cities reduced to shells. Germany was set back almost two centuries; it would not regain its earlier stature until well into the nineteenth century.
Anti-rationalism had one last spasm in the seventeenth century: the witch-hunts. Most Americans recall the Salem witch trials with horror, but they were only the local version of a phenomenon that blanketed Europe. Every country burned and hanged witches; the practice had been well-established throughout the Middle Ages. During the old days, however, the itch to burn people could more easily be satisfied by burning heretics, and so witch-burning was rare until the seventeenth century. Sometime in the early 1600s the practice of burning witches became more popular, and continued off and on for a hundred years.
What is particularly striking about the phenomenon is the abruptness of its ending. The Salem witch trials were followed just a few years later with public demonstrations of remorse by all concerned. The witch-hunting was always the work of religious zealots; eventually their thirst for blood sickened decent people enough to encourage them to put a stop to the killing.
By the dawn of the eighteenth century, people had developed a healthy fear of the dangers of religious zealotry. They recognized a need for something other than religion to guide behavior, something that would enforce the good without imposing any particular religious behaviors. The answer was provided to them by science.
Galileo Galilei had started the movement around 1640. He wasn't the first modern scientist by any stretch, but he came at the right time. His scientific discoveries were important in a negative sense: he challenged Catholic orthodoxy. This was the first showdown between science and religion. The fundamental problem was that both religion and science, at their heart, attempt to explain the nature of the universe. Nowadays, we sidestep that problem by drawing a line between religion and science, according to religion the task of answering "why?" questions and to science the task of answering "how?" questions. Even so, many people are confused over this distinction, and certainly back in the seventeenth century the distinction was lost on everybody.
In an ironic twist, the first battle between religion and science arose over a point that had arisen from Christianity's embrace of Aristotelianism. Many of Aristotle's teachings on physics were just plain wrong, and it didn't take much experimenting to expose the fallacy's in Aristotle's version of physics. When Galileo did just that, he antagonized the Catholic Church and eventually got himself into hot water. But in northern Europe, the Church had no temporal power and so scientists there proceeded unhindered. And by persecuting Galileo, the Church succeeded only in discrediting itself. Galileo's experiments were easily reproducible; anybody could try them out and see for himself that Galileo was right. As a result, confidence in religion fell.
It was an Englishman, Isaac Newton, who blew open the doors to science. Newton's work launched the Age of Reason, a happy period in which Europeans believed that all the world's problems could be solved with Reason -- that is, sequential thinking. The emotional impact Newton had on his age is hard for us to comprehend. The poet Edmund Pope pretty well said it all in a couplet: "Nature and Nature's secrets lay hid in night; God said, 'Let Newton be!' and all was light!"
Newton was a devout Christian; he felt that his researches served to glorify God. But confidence in religion as the central guide to life was waning and people needed to believe that there existed some alternative to utter anarchy of belief. Newton's work demonstrated that the universe obeyed absolute laws. The implication was that, with further research, the clockwork of the universe would soon be laid bare and men could solve any problem with reason.
Newton's success inspired the Western world. The giddy realization that every motion, every action in the universe could be calculated (at least theoretically) seized the imagination and transformed the Western view of the universe. A host of thinkers and scholars followed up Newton's work with ever more detailed applications, each one further proclaiming the omnipotence of this new logic of mathematics and nature. As Newton had said, borrowing from Bernard of Chartres, he saw further only because he stood on the shoulders of giants. Those giants -- Galileo and Descartes in particular -- lent their shoulders to Newton, and many others refined, developed, and expanded his work, but it was Newton who opened the door to the Age of Reason.
The Age of Reason lasted a bit more than a century; it was smothered in the bloody convulsions that swept Europe during the Napoleonic Wars. During that time, however, Reason established its grip on the imagination of Western civilization. Although the real world was a messy, ugly place, people firmly beleived that the light of pure reason would eventually lead mankind into a glorious new world of peace, justice, and prosperity.