To understand the natural world and mankind's place in it solely on the basis of reason and without turning to religious belief-this was the goal of the wide ranging intellectual movement called the enlightenment. The movement claimed the allegiance of a majority of thinkers during the 17th and 18th centuries, a period that Thomas Paine called the Age of Reason. At its heart it became a conflict between religion and the inquiring mind that wanted to know and understand through reason based on evidence and proof.
Like all historical trends and movements, the enlightenment had its roots in the past. Three of the chief sources for Enlightenment thought were the ideas of the ancient Greek philosophers, the Renaissance, and the scientific revolution of the Middle Ages.
The ancient philosophers had noticed the regularity in the operation of then natural world and concluded that the reasoning mind could see and explain this regularity. Among these philosophers Aristotle was preeminent in discovering and explaining the natural world.
The birth of Christianity interrupted philosophical attempts to analyze and explain purely on the basis of reason. Christianity built a complicated world view that relied on both faith and reason to explain reality.
The Renaissance, with its revival of classical learning, and the Reformation of the 16th century, which broke up the Christian church, ended the world view that the church had presented for a thousand years. Coupled with these events was the scientific revolution, a modern discipline that soon lost patience with religious quibbling and what was seen as the attempts of churches to hamper progress in thought. Among the leaders of this revolution were Francis Bacon, Rene Descartes, Copernicus, Galileo, Gottfried Leibniz, and-most significant of all - Sir Issac Newton. It was Newton who explained the universe and who justified the rationality of nature.
Religious Issue
The response of organized religion to the avalanche of new ideas and facts was far from friendly. A perfect example of this is that Galileo was called before the Inquisition in Rome and forced to take back his statements that the sun, not the earth , is the center of the solar system.
But religion in the 17th and 18th centuries was on the defensive, and the great number of new denominations after the Reformation made a united front impossible. While most early supporters of rationalism and new scientific methods did not deny either God or religion, they brought both under the microscope of reason. They were negative about biblical religion and Christianity while expressing a belief in a God who was the author of nature's wonders, a God who had set the world in motion and formulated the laws by which it operated. This religious view - called deism-found many followers during the enlightenment, but it was never an organized religion like Christianity.
Eventually both Christianity and its deistic opponents were faced with an extreme rejection of religion in an upsurge of atheism, the denial of God's existence. This reaction had its roots in the ancient philosophy of materialism that had been set forth by Epicurus and his followers-a world of atoms and empty space and nothing more. If reason could not discover God, said the atheists, there was no purpose served by deciding there was one.