Sir Isaac Newton and Rene Descartes

Newton and Descartes both accepted Galileo’s revision of classical and medieval knowledge; but offered contrasting theories of Scientific Knowledge. Kepler, Galileo, and the other early scholars of the Scientific Revolution completely discredited Aristotelian theory, but did not synthesize their findings into a single comprehensive conclusion. That synthesis was completed by Sir Isaac Newton. (1642 – 1727)

Rene Descartes: used deductive reasoning, deducing a conclusion from a set of premises, to determine the nature of the Universe. This was contrary to other great thinkers of the time who used scientific observation. In 1637, he published his Discourse on Method, in which he discussed his rejection of the scientific teaching he encountered as a young man. He argued that too much of what had been taught had been based on tradition without critical commentary. He therefore "resolved no longer to seek any other science than the knowledge of myself or of the great book of the world."

Descartes stated that a person must begin with a blank slate, the famous tabula rasa, to understand the world through deductive reasoning. In his famous discourse, he at first questioned his own existence, but postulated that he did exist in his famous statement, Cognito Ergo Sum (I think, therefore I am.). To Descartes, the ability to think was the basis of human existence. Thereafter each problem had to be separated, "into as many parts as may be necessary for its adequate solution." That way, one could move from the simplest idea to the most complicated, similar to mathematical computation. The world could be reduced to two substances, "Mind," the "thinking substance;" and "matter," the "extended substance." Hence the famous expression of "mind over matter." (Growing old is often a problem of mind over matter: If you don’t mind, it doesn’t matter!)

Descartes defined matter as the infinite number of particles that fill all space. There was no void or vacuum. This, he said, could be discovered and described mathematically, as could the laws of motion. He argued that the existence of the material universe and even the existence of God could be deduced. "Begin with the smallest object, the easiest to understand, and gradually move to a knowledge of those that are the most complex.

Descartes’ theories left no room for medieval or ancient tradition. As a sign of the break of the old with the new, he published his work in French, rather than the traditional Latin, describing the latter as the language of ecclesiastical doctrine and scholasticism. His concept of God was similar to that of Kepler: God was a giant clockmaker who created the universe according to rules that the human mind could understand with proper reasoning. God then stepped back, and completely removed Himself from the workings of His creation.

Descartes’ chief contribution is the theory that reason, not experimentation, is the proper method by which truth may be discovered. Mathematics was the foundation of all science, and demonstrated "the certainty and self-evidence of its reasonings." Eventually a mathematical rule would be discovered that would explain every natural phenomenon. It could all be reduced to a simple matter of mathematical computation, once one discovered the correct formula, which one would discover by reason, not computation.

A rationalist rather than a scientist, Descartes attracted many followers On one occasion one poor soul, not appreciating Descartes’ disdain for experimentation, asked to see his instruments. Descartes recalled that he "would drawe out a little Drawer under his Table, and shew them a paire of Compasses, with one of the Legges broken; and then, for his Ruler, he used a sheet of paper folded double." Share that with your geometry teacher!

Newton: Sir Isaac was born into a gentleman family in England and attended Cambridge University where he demonstrated genius. He specialized in uniting experimental and theoretical elements of modern science. He was fascinated with alchemy, the belief that with the use of a catalyst known as the "philosopher’s stone," one element could be converted into another, the most famous illustration being the conversion of lead into gold. Although he has often been characterized as the perfect rationalist, he was in fact intensely religious.

Newton suffered from bipolar disorder, and frequently shut himself in his chambers for days on end, leaving only to deliver lectures at Cambridge where he was professor of mathematics. His meals were left at his door, and often left uneaten. In 1684, he began an intensive study of physics that lasted for eighteen months. In the opening lines of the third book of his Principia Mathematica (Mathematical Principals of Natural Philosophy), he wrote:

In the preceding books I have laid down the principles of philosophy (that is, science)….These principles are the laws of certain         motions and powers or forces, which chiefly have respect in philosophy….It remains that from the same principles I now demonstrate the frame of the System of the World.

The Principia was the first synthesis of scientific principles. Newton combined Galileo’s experimental practice (empiricism) with Descartes’ logic and rigor, and thereby developed the theory of modern science: theory and experimentation combined into a single discipline.

The story of Newton observing a falling apple is in fact true. He was sitting under a tree on his family farm ruminating about celestial motion, when he saw the apple fall. He recognized that the force that causes objects to fall to the ground was the same force that kept the planets in motion. He theorized that Kepler’s law of planetary motion would be correct if the planets war being pulled toward the sun by a force whose strength was in inverse proportion to their distance from it.

On the basis of this theory, Newton developed a system of mathematical laws that explained motion and mechanics. The key feature of his work was the law of universal gravity: Every body in the universe attracts every other body in the universe in a precise mathematical relationship, whereby the force of attraction is proportional to the quantity of matter of the objects and inversely proportional to the square of the distance between them. (*whew!*) His theory unified Kepler’s universe with Galileo’s rolling balls. He went beyond Kepler’s three laws of planetary motion and postulated a theory of universal gravitation, the existence of forces of attraction and repulsion between objects.

Newton also calculated, correctly, that the density of the earth is five and one half times that of water, and theorized (incorrectly) that electrical impulses activated the central nervous system. His theories were the forerunners of quantum physics and thermodynamics. He was the first to understand that all colors are composed of a mixture of the primary colors of the spectrum, and explained the phenomena of rainbows. He also calculated sound waves and invented calculus, a fact for which every advanced placement student will be eternally grateful. (Calculus was invented simultaneously by a German scholar, Gottfried Liebniz.) Newton also constructed the first reflecting telescope (previous telescopes had used refractive lens) and wrote a paper on optics in which he postulated that light could be mathematically described and analyzed. His work is often considered the beginning of theoretical physics.

Newton disagreed with Descartes as he believed that Descartes described the world as comprised totally of matter and thereby eliminated God from the equation. Newton, devoutly religious, believed that God did intervene from time to time to keep the great clock running, otherwise it would run down. He wrote several manuscripts on religious doctrine in which he seemed to indicate that science and religion were not necessarily inconsistent with one another.

Although his predecessors never saw fame during their lifetimes, Newton became wealthy and a hero in his own lifetime. He was elected to Parliament in 1609 as the representative of Cambridge University, and became warden of the Royal Mint, and was knighted by the King. Even so, he was something of a weirdo. He was humorless and published his findings with reluctance, normally only when he feared that a rival might be him to the punch. He accused those working on similar problems of copying him, and was not generous in acknowledging that which he learned from others. He did, however, pay tribute to the work of Galileo by stating, "If I have seen further than others, it is because I have stood on the shoulders of giants." Alexander Pope, the English Poet, paid tribute to Newton’s discoveries in a famous verse:

                                    Nature and Nature’s laws were hid in night.
                                    God said, Let Newton be! And there was light.

On his death, Newton was given a state funeral, and buried in Westminster Abbey.

The followers of Newton and Descartes often engaged in intense scientific debate as to the correctness of their respective positions. A Dutch philosopher and mathematician, Baruch Spinoza (1632 – 1677) supported the Cartesians (followers of Descartes) by theorizing that thought and matter comprised the two categories of reality. Gottfried Liebniz also agreed with Descartes and rejected Newton’s theory that God had to intervene from time to time to keep the machinery running. He concluded that the universe was, like God, infinite in space and time. The bodies of animals and humans ran like clocks that were set in motion, as was the universe. His thinking that God created the universe to run on its own without intervention constituted the hallmark of the "new philosophy."