Isaac Newton's Principia Mathematica Greatly Influences the Scientific World and the Society Beyond It

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Isaac Newton's Principia Mathematica Greatly Influences the Scientific World and the Society Beyond It

Overview

Isaac Newton's (1642-1725) most influential writing was his Philosophiae Naturalis Principia Mathematica (The Mathematical Principles of Natural Philosophy), published in sections between the years 1667-86. It united two competing strands of natural philosophy—experimental induction and mathematical deduction—into the scientific method of the modern era. His emphasis on experimental observation and mathematical analysis changed the scope and possibilities of science.

Background

Throughout the medieval period European scholars had relied heavily on the teachings of Aristotle (384-322 b.c.) and the works of a few Christian philosophers. Then, in the late fifteenth century, there was a rediscovery and popularization of other ancient writers, such as Plato (427-347 b.c.), who opposed many of Aristotle's ideas. The intellectual community began to debate the works of these and other ancient writers, often challenging firmly held academic and religious beliefs. However, these debates were framed by the question of which of the ancient writers was correct. Some thinkers began to question the basis of such debate, arguing that new forms of thinking could go beyond the works of the ancients.

René Descartes (1596-1650) found the Aristotelian methods he was taught to be entirely unsatisfactory. He considered them to be based on false assumptions. The only knowledge he found certain was mathematics, and so he used mathematical deduction as the basis of his entire scientific method and philosophy. Descartes' most comprehensive work was his Principia Philosophiae (1644), which attempted to put the whole universe on a mathematical foundation, reducing the study of everything to that of mechanics. For Descartes, knowledge could only be gained from deduction from fundamental principles.

Deduction is the method by which consequences are derived from established premises. From the observed or established facts predictions of future events or possible consequences can be deduced. In a sense it is an educated guess. For example, from the premise that all swans are white, if the bird you observe is a swan, then deductively the bird must also be white. As long as the premise and observation are correct then the conclusion must be true. However, deduction can never prove the premise, no matter how much supporting evidence is gathered, as a single contradictory result will overturn the rule. Black swans were discovered in Australia, and so the deduction was incorrect.

Galileo Galilei (1564-1642) also championed the notion of deduction, although in his case from experimental observations. He found the academic focus on ancient knowledge to be suffocating and limiting. He used experimental deduction to show that the universe was not as he had been taught. He observed the mountains and craters of the Moon, which tradition held was a perfect sphere. He saw moons orbiting Jupiter, and observed that the Milky Way was made up of tiny stars. From these observations he deduced that Earth was not the center of the universe, that the planets were not perfect and unchanging, and that the Copernican theory (that Earth revolved around the Sun, not vice versa) was correct.

An alternative to both the reliance on ancient writings and the deductive method was proposed by Francis Bacon (1561-1626). Bacon dismissed deduction as merely the logic of argumentation. He preferred induction, which is the process of reasoning from particular events to general rules. For example, when numerous observations of swans also gave the result that all observed swans are white, then it was induced that all swans were white. As we have seen, this is not correct.

Bacon did not think that scientists should seek to prove particular theories as Galileo had done. He proposed that scientists should unselectively and objectively collect facts from experiment and observation and then organize and classify them. When enough facts had been collected, then they would be generalized to create a universal theory.

Another inductive thinker was Robert Boyle (1627-1691). His 1661 work The Sceptical Chemist argued against Aristotle's views on the composition of matter. His experimental work was wide and varied, and only when he had performed numerous variations of an experiment would he then induce general rules to explain the results.

Like these other scientists, Newton also found the stale debates over ancient writings to be frustrating. Initially he turned to the mathematical deduction of Descartes as an escape from Aristotle. However, the more he considered Descartes's ideas the more he disagreed. He was also influenced by the works of Nicolaus Copernicus (1473-1543), Johannes Kepler (1571-1630), and Galileo, and began to combine them all together. The work that resulted was his Principia Mathematica.

Newton's Principia was mainly a description of the laws of planetary motion. However, it also contained more universal material that was to influence the way all science developed. In effect it combined the methods of induction and deduction. Newton agreed with the inductionists that first a scientist should establish the facts by careful observation and experiment. However, he then proposed using deduction from already known principles to formulate new hypothetical principles. Then laws of nature could then be induced. These new laws could be tested by further experiment and observation, and so on.

Impact

The Principia received good reviews, perhaps because some were written by close friends of Newton. The book was an all-encompassing explanation of physics, starting with definitions of mass, force, and motion, providing mathematical explanations of these principles, and going on to explain planetary motion, lunar motion, the ocean tides, and many other things besides.

Descartes had stressed the importance of mathematics, and on this point Newton agreed. The Principia established mathematics as the language of science. Mathematics became a means of knowing about the universe. However, the Principia was directly, and deliberately, opposed to Descartes' philosophy. Newton fundamentally disagreed with the separation of spirit from matter that existed in Descartes' mechanical view of the world. In part Newton's work was an attempt to restore the place of God in science. Newton used his mathematical method to show that Descartes' system of mechanics was impossible.

However, despite the problems with Descartes' theories they remained popular on the European continent, particularly in France, for nearly one hundred years. There were, however, a number of non-British scientists who followed Newton's ideas. The prominent French intellectual Voltaire (1694-1778) was in England at the time of Newton's funeral, and was impressed with the scientific culture he found there. He wrote a glowing description of the British intellectual climate, but these writings were immediately banned in France.

The Principia provided a standard for doing scientific investigations, and with his other published works, such as Opticks (1704), formed the cornerstone for the modern scientific method. It offered a coherent method that seemed free of the occult and reliance on the ancients. However, Newton's influences included alchemy, unorthodox religious ideas, and a belief that God had given the ancients the true secrets of science and religion.

The Principia's focus on experiment and observation seems to owe much to the ideas of Bacon. Yet Newton had been more strongly affected by alchemical philosophy, partly because of its mystical and religious elements. He found alchemy's reliance on experiment to be more solid than many other forms of study. He also preferred its description of the universe as a living force over the mechanical philosophy of Descartes. Newton wrote over a million words on his alchemical studies, but published nothing.

Newton had been careful to include God in his overall plan of the universe. Against Newton's wishes later followers of his ideas tended to reduce, or eliminate completely, the religious aspect of his theories. Later editions of the Principia often edited out the philosophical sections, and emphasized Newton's mechanics. In a sense the mechanical views of Descartes were eventually triumphant, but only within the setting of Newton's theories.

Newton's success enabled him to wield great influence in British scientific affairs. He was careful to promote the careers of those who supported his ideas, and obstruct those who opposed him. A culture of Newtonianism grew, helping to spread the ideas and changing the way science was performed. Britain developed a more practical and hands-on scientific approach than the rest of Europe. The emphasis on experiments was different from the contemplative, hands-off philosophy that remained popular elsewhere.

Newton's methods lent themselves easily to everyday applications in mining, agriculture, and industry. Newtonian mechanics could be applied to drain swamps, construct bridges, and pump air into deep mines. Newton's writings helped change the perspective of his followers, and they saw the world with practical, and mechanical, eyes.

The ideas of the Principia were used outside of science as well. Indeed, Newtonian mechanics was applied to almost anything, including society itself. John Locke's (1632-1704) democratic philosophy, one of the sparks of the revolutionary period, used Newtonian concepts. Newton even revolutionized the Freemasons (a fraternal order who adopted the rites of ancient religious orders), who introduced new rituals modeled on his philosophy.

Newton's writings took on the form of doctrine to many later scientists, particularly in England. His findings were often held to be unshakable, even when experiments and analysis using his own method showed them to be wrong. In the eighteenth century many physicists insisted that there were only seven colors, the ones Newton had shown with his prisms. Work that contradicted the old master was discouraged or denied. In nineteenth-century England there was fierce resistance to the wave-theory of light, as it opposed Newton's corpuscular model. While the culture of Newtonianism helped spark the Industrial Revolution, it later held back research into new areas.

Newton's ideas were practical, and his method allowed predictions and discoveries to be made. Perhaps the most spectacular use of Newton's laws of planetary motion were the calculations made by U. J. J. Le Verrier (1811-1877). On the basis of slight variations from Newtonian calculations of the orbit of Uranus he predicted the existence of a new planet, Neptune. However, a similar wobble in the orbit of Mercury was shown by Albert Einstein (1879-1955) not to be caused by another planet, but rather due to effects of relativity, which was to supersede Newtonian mechanics in the twentieth century.

DAVID TULLOCH