Science, Rationalism and the Enlightenment

Descartes, Image: Wikipedia

In our discussion of the ten commandments and the postmodern alternative, I managed to get a bit ahead of myself.  While our founders were clearly influenced by the Hebrews and the thinking of the Greek and Roman philosophers, there was an alternative brewing largely in Europe at the same time.


The age of enlightenment in the mid 1700’s was led by thinkers such as Voltaire, Descartes, and Montesquieu in France, and Kant and Mendelssohn in Germany.  With great advances being made in science, both natural and social sciences, these philosophers believed that a new world was dawning and that mankind would be greatly improved by these advances.  Scientific advancements called into question some of the former assumptions about the universe and the world in which they lived.  As science began to answer these questions, it caused these philosophers to question some of the other assumptions of the ancients.  They envisioned science leading to “the century of philosophy par excellence”.


Of particular interest to us as we explore the thinking that drove western civilization, is to look at the philosophy of the enlightenment in France which took place at roughly the same time as the American founding.  The US constitution was ratified in 1788 and the French revolution took place in 1789.  For the sake of simplicity, we can call the “Reign of Terror” (1792-3 depending on who you ask) in France the end of the enlightenment.


The French monarchy, the idea of nobility, and the Catholic church all came under attack by the philosophy of the enlightenment.  Remember that Plato felt that the organization of society was ordained naturally.  The balance of reason, spirit and appetite, varied by individual and suited certain people to certain roles. A philosopher king would rule naturally because he was best suited to that role.  Those who were ruled by their appetites could hardly be expected to rule, let alone have learned opinions.  The Church acted as a restraint on the monarchy only at the margins, and while all monarchs knew that they would answer to God in the end, they also felt that they were ordained to rule.  And the Church, as any institution run by man, had its many flaws.  While not all of the philosophers of the enlightenment wanted to rid the world of religion, they did want a society based on reason and science with the ideals of liberty and equality.  Kant was a key driver in this movement and he defined the purpose of the enlightenment as a maturing of the human philosophy defining the alternative as, “the inability to use one’s own understanding without the guidance of another.”  He believed that man should be capable of arriving at conclusions using only his own reason.  Man’s own intellectual capabilities were sufficient.  He and his followers believed that the enlightenment was more than a philosophy, it was a process that would become self-perpetuating, in that a person’s perceptions would improve with practice and that would further improve their sense of perception in a virtuous cycle.  This process would lead to a better life for both the individual and for society.


The first advances of the enlightenment period could be described as a time of science and rationalism. The often-cited beginning of this movement was Isaac Newton’s work with astrology.  Using a few simple mathematical formulas, he described the movement of planets relative to the sun in Principa Mathamatica published in 1687.  Because Newton was able to describe this complex movement in a brilliantly simple mathematical manner, people came to believe that the most complex universal questions could be known by humans and their powers of reason.  The study of nature became a central premise of the enlightenment as these philosophers sought to use this method to better comprehend the previously incomprehensible.  While Newton clearly showed that the movement of planets could be defined mathematically, he still believed in God.  “Atheism is so senseless. When I look at the solar system, I see the earth at the right distance from the sun to receive the proper amounts of heat and light. This did not happen by chance.”


Descartes believed that the best method for exploring the natural world was his “method of doubt”.  He began all inquiry with doubting everything that could be doubted. He felt that this skepticism was key to discovering metaphysical truths. Like Plato he doubted the veracity of what our senses perceive. His most famous formulation was that the mind and body were two distinct substances and that the world of perception, that which we experience in the world, is our external world, whereas our God and the soul are innate to us and not subject to our perceptions.  In Descartes understanding, all knowledge comes from a metaphysical understanding of God, of understanding His nature, His first principles.


Science owes Descartes a great deal.  The concept of matter begins with Descartes and that work was critical to the ability to use physics to describe matter in a mathematical way.  He also was responsible for using mathematical formulas to define geometric problems.  Newtonian physics starts with Descartes work as Newton himself admitted.


Along with these significant credits, Descartes was also responsible for some of the great controversy in the philosophy of the Enlightenment.  The concept of the mind and the body being two separate substances was a cause for a great deal of angst.  If they are indeed separate, how are they related?  Descartes did not have a solution for that problem.  If Descartes’ mathematical models describe the movement of matter, and matter is inert (as he believed) what is the cause of movement?  And finally, his defining of God as the key to all understanding caused problems for people who believed in only that which can be observed.


Baruch Spinoza attempted to solve the problem of two substances that Descartes created by stating that there was only one substance, with two natures, mind and body, and God and nature.  But Spinoza broke with Descartes and Newton as he identified God with nature, not as a separate transcendental being.


The German philosopher Leibniz, added to this the theory of “sufficient reason”.  He hypothesized that everything that exists has a sufficient reason for that existence.  This is perhaps the best way of summarizing the movement.  To the philosophers of the enlightenment, all of nature was rational and could therefore be explained.


In addition to the advances of science, the enlightenment also brought forward the concept of empiricism.  The concept that all truth must be based on evidence.  We will explore that a bit more next time.

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