The Turning Point (Chapter 2--excerpted)
According to legend, the decisive insight occurred to Newton in a sudden flash of inspiration when he saw an apple fall from a tree. He realized that the apple was pulled toward the earth by the same force that pulled the planets toward the sun, and thus found the key to his grand synthesis. He then used his new mathematical method to formulate the exact laws of motion for all bodies under the influence of the force of gravity. The significance of these laws lay in their universal application. They were found to be valid throughout the solar system and thus seemed to confirm the Cartesian view of nature. The Newtonian universe was, indeed, one huge mechanical system, operating according to exact mathematical laws.
Newton presented his theory of the world in great detail in his Mathematical Principles of Natural Philosophy. The Principia, as the work is usually called for short after its original Latin title, comprises a comprehensive system of definitions, propositions, and proofs which scientists regarded as the correct description of nature for more than two hundred years. It also contains an explicit discussion of Newton's experimental method, which he saw as a systematic procedure whereby the mathematical description is based, at every step, on critical evaluation of experimental evidence:
Whatever is not deduced from the phenomena is to be called a hypothesis; and hypotheses, whether metaphysical or physical, whether of occult qualities or mechanical, have no place in experimental philosophy. In this philosophy, particular propositions are inferred from the phenomena, and afterwards rendered general by induction.2
Before Newton there had been two opposing trends in seventeenth-century science; the empirical, inductive method represented by Bacon and the rational, deductive method represented by Descartes. Newton, in his Principia, introduced the proper mixture of both methods, emphasizing that neither experiments without systematic interpretation nor deduction from first principles without experimental evidence will lead to a reliable theory. Going beyond Bacon in his systematic experimentation and beyond Descartes in his mathematical analysis, Newton unified the two trends and developed the methodology upon which natural science has been based ever since.
Isaac Newton was a much more complex personality than one would think from a reading of his scientific writings. He excelled not only as a scientist and mathematician but also, at various stages of his life, as a lawyer, historian, and theologian, and he was deeply involved in research into occult and esoteric knowledge. He looked at the world as a riddle and believed that its clues could be found not only through scientific experiments but also in the cryptic revelations of esoteric traditions. Newton was tempted to think, like Descartes, that his powerful mind could unravel all the secrets of the universe, and he applied it with equal intensity to the study of natural and esoteric science. While working at Trinity College, Cambridge, on the Principia, he accumulated, during the very same years, voluminous notes on alchemy, apocalyptic texts, unorthodox theological theories, and various occult matters. Most of these esoteric writings have never been published, but what is known of them indicates that Newton, the great genius of the Scientific Revolution, was at the same time the 'last of the magicians."24
The stage of the Newtonian universe, on which all physical phenomena took place, was the three-dimensional space of classical Euclidean geometry. It was an absolute space, an empty container that was independent of the physical phenomena occurring in it. In Newton's own words, 'Absolute space, in its own nature, without regard to anything external, remains always similar and immovable.'25 All changes in the physical world were described in terms of a separate dimension, time, which again was absolute, having no connection with the material world and flowing smoothly from the past through the present to the future. 'Absolute, true, and mathematical time,' wrote Newton, 'of itself and by its own nature, flows uniformly, without regard to anything external.'26
The elements of the Newtonian world which moved in this absolute space and absolute time were material particles; small, solid and indestructible objects out of which all matter was made. The Newtonian model of matter was atomistic, but it differed from the modern notion of atoms in that the Newtonian particles were all thought to be made of the same material substance. Newton assumed matter to be homogeneous; he explained the difference between one type of matter and another not in terms of atoms of different weights or densities but in terms of more or less dense packing of atoms. The basic building blocks of matter could be of different sizes but consisted of the same 'stuff,' and the total amount of material substance in an object was given by the object's mass.
The motion of the particles was caused by the force of gravity, which, in Newton's view, acted instantaneously over a distance. The material particles and the forces between them were of a fundamentally different nature, the inner constitution of the particles being independent of their mutual interaction. Newton saw both the particles and the force of gravity as created by God and thus not subject to further analysis. In his Opticks, Newton gave a clear picture of how he imagined God's creation of the material world:
It seems probable to me that God in the beginning formed matter in solid, massy, hard, impenetrable, movable particles, of such sizes and figures, and with such other properties, and in such proportion to space, as most conduced to the end for which he formed them; and that these primitive particles being solids, are incomparably harder than any porous bodies compounded of them; even so very hard, as never to wear or break in pieces; no ordinary power being able to divide what God himself made one in the first creation.27
In Newtonian mechanics all physical phenomena are reduced to the motion of material particles, caused by their mutual attraction, that is, by the force of gravity. The effect of this force on a particle or any other material object is described mathematically by Newton's equations of motion, which form the basis of classical mechanics. These were considered fixed laws according to which material objects moved, and were thought to account for all changes observed in the physical world. In the Newtonian view, God created in the beginning the material particles, the forces between them, and the fundamental laws of motion. In this way the whole universe was set in motion, and it has continued to run ever since, like a machine, governed by immutable laws. The mechanistic view of nature is thus closely related to a rigorous determinism, with the giant cosmic machine completely causal and determinate. All that happened had a definite cause and gave rise to a definite effect, and the future of any part of the system could - in principle - be predicted with absolute certainty if its state at any timewas known mail details.
This picture of a perfect world-machine implied an external creator; a monarchical god who ruled the world from above by imposing his divine law on it. The physical phenomena themselves were not thought to be divine in any sense, and when science made it more and more difficult to believe in such a god, the divine disappeared completely from the scientific world view, leaving behind the spiritual vacuum that has become characteristic of the mainstream of our culture. The philosophical basis of this secularization of nature was the Cartesian division between spirit and matter. As a consequence of this division, the world was believed to be a mechanical system that could be described objectively, without ever mentioning the human observer, and such an objective description of nature became the ideal of all science.
The eighteenth and nineteenth centuries used Newtonian mechanics with tremendous success. The Newtonian theory was able to explain the motion of the planets, moons, and comets down to the smallest details, as well as the flow of the tides and various other phenomena related to gravity. Newton's mathematical system of the world established itself quickly as the correct theory of reality and generated enormous enthusiasm among scientists and the lay public alike. The picture of the world as a perfect machine, which had been introduced by Descartes, was now considered a proved fact and Newton became its symbol. During the last twenty years of his life Sir Isaac Newton reigned in eighteenth-century London as the most famous man of his time, the great white-haired sage of the Scientific Revolution. Accounts of this period of Newton's life sound quite familiar to us because of our memories and photographs of Albert Einstein, who played a very similar role in our century.
Encouraged by the brilliant success of Newtonian mechanics in astronomy, physicists extended it to the continuous motion of fluids and to the vibrations of elastic bodies, and again it worked. Finally, even the theory of heat could be reduced to mechanics when it was realized that heat was the energy generated by a complicated 'jiggling' motion of atoms and molecules. Thus many thermal phenomena, such as the evaporation of a liquid, or the temperature and pressure of a gas, could be understood quite well from a purely mechanistic point of view.
The study of the physical behavior of gases led John Dalton to the formulation of his celebrated atomic hypothesis, which was probably the most important step in the entire history of chemistry. Dalton had a vivid pictorial imagination and tried to explain the properties of gas mixtures with the help of elaborate drawings of geometric and mechanical models of atoms. His main assumptions were that all chemical elements are madeupof atoms,and that the atoms of a given element are all alike but differ from those of every other element in mass, size, and properties. Using Dalton's hypothesis, chemists of the nineteenth century developed a precise atomic theory of chemistry which paved the way for the conceptual unification of physics and chemistry in the twentieth century. Thus Newtonian mechanics was extended far beyond the description of macroscopic bodies. The behavior of solids, liquids, and gases, including the phenomena of heat and sound, was explained successfully in terms of the motion of elementary material particles. For the scientists of the eighteenth and nineteenth centuries this tremendous success of the mechanistic model confirmed their belief that the universe was indeed a huge mechanical system, running according to the Newtonian laws of motion, and that Newton's mechanics was the ultimate theory of natural phenomena.
Although the properties of atoms were studied by chemists rather than physicists throughout the nineteenth century, classical physics was based on the Newtonian idea of atoms as hard and solid building blocks of matter. This image no doubt contributed to the reputation of physics as a ^ard science,1 and to the development of the 'hard technology' based upon it. The overwhelming success of Newtonian physics and the Cartesian belief in the certainty of scientific knowledge led directly to the emphasis on hard science and hard technology in our culture. Not until the mid-twentieth century would it become clear that the idea of a hard science was part of the Cartesian-Newtonian paradigm, a paradigm that would be transcended.
With the firm establishment of the mechanistic world view in the eighteenth century, physics naturally became the basis of all the sciences. If the world is really a machine, the best way to find out how it works is to turn to Newtonian mechanics. It was thus an inevitable consequence of the Cartesian world view that the sciences of the eighteenth and nineteenth centuries modeled themselves after Newtonian physics. In fact, Descartes was well aware of the basic role of physics in his view of nature. "All philosophy,' he wrote, 'is like a tree. The roots are metaphysics, the trunk is physics, and the branches are all the other sciences.'28
Descartes himself had sketched the outlines of a mechanistic approach to physics, astronomy, biology, psychology, and medicine. The thinkers of the eighteenth century carried this program further by applying the principles of Newtonian mechanics to the sciences of human nature and human society. The newly created social sciences generated great enthusiasm, and some of their proponents even claimed to have discovered a 'social physics.' The Newtonian theory of the universe and the belief in the rational approach to human problems spread so rapidly among the middle classes of the eighteenth century that the whole era became the 'Age of Enlightenment.' The dominant figure in this development was the philosopher John Locke, whose most important writings were published late in the seventeenth century. Strongly influenced by Descartes and Newton, Locke's work had a decisive impact on eighteenth-century thought.
Following Newtonian physics, Locke developed an atomistic view of society, describing it in terms of its basic building block, the human being. As physicists reduced the properties of gases to the motion of their atoms, or molecules, so Locke attempted to reduce the patterns observed in society to the behavior of its individuals. Thus he proceeded to study first the nature of the individual human being, and then tried to apply the principles of human nature to economic and political problems. Locke's analysis of human nature was based on that of an earlier philosopher,
Thomas Hobbes, who had declared that all knowledge was based on sensory perception. Locke adopted this theory of knowledge and, in a famous metaphor, compared the human mind at birth to a tabula rasa, a completely blank tablet on which knowledge is imprinted once it is acquired through sensory experience. This image was to have a strong influence on two major schools of classical psychology, behaviorism and psychoanalysis, as well as on political philosophy. According to Locke, all human beings - 'all men,' as he would say - were equal at birth and depended in their development entirely on their environment. Their actions, Locke believed, were always motivated by what they assumed to be their own interest.
When Locke applied his theory of human nature to social phenomena, he was guided by the belief that there were laws of nature governing human society similar to those governing the physical universe. As the atoms in a gas would establish a balanced state, so human individuals would settle down in a society in a 'state of nature.' Thus the function of government was not to impose its laws on the people, but rather to discover and enforce the natural laws that existed before any government was formed. According to Locke, these natural laws included the freedom and equality of all individuals as well as the right to property, which represented the fruits of one's labor.
Locke's ideas became the basis for the value system of the Enlightenment and had a strong influence on the development of modern economic and political thought. The ideals of individualism, property rights, free markets, and representative government, all of which can be traced back to Locke, contributed significantly to the thinking of Thomas Jefferson and are reflected in the Declaration of Independence and the American Constitution.
During the nineteenth century scientists continued to elaborate the mechanistic model of the universe in physics, chemistry, biology, psychology, and the social sciences. As a result the Newtonian world-machine became a much more complex and subtle structure. At the same time, new discoveries and new ways of thinking made the limitations of the Newtonian model apparent and prepared the way for the scientific revolutions of the twentieth century.
One of these nineteenth-century developments was the discovery and investigation of electric and magnetic phenomena that involved a new type of force and could not be described appropriately by the mechanistic model. The important step was taken by Michael Faraday and completed by Clerk Maxwell - the first one of the great experimenters in the history of science, the second a brilliant theorist. Faraday and Maxwell not only studied the effects of the electric and magnetic forces, but made the forces themselves the primary object of their investigation. By replacing the concept of a force with the much subtler concept of a force field they were the first to go beyond Newtonian physics,29 showing that the fields had their own reality and could be studied without any reference to material bodies. This theory, called electrodynamics, culminated in the realization that light was in fact a rapidly alternating electromagnetic field traveling through space in the form of waves.
In spite of these far-reaching changes, Newtonian mechanics still held its position as the basis of all physics. Maxwell himself tried to explain his results in mechanical terms, interpreting the fields as states of mechanical stress in a very light, all-pervasive medium called ether, and the electromagnetic waves as elastic waves of this ether. However, he used several mechanical interpretations of his theory at the same time and apparently took none of them really seriously, knowing intuitively that the fundamental entities in his theory were the fields and not the mechanical models. It remained for Einstein to clearly recognize this fact in our century, when he declared that no ether existed, and that the electromagnetic fields were physical entities in their own right which could travel through empty space and could not be explained mechanically.
While electromagnetism dethroned Newtonian mechanics as the ultimate theory of natural phenomena, a new trend of thinking arose that went beyond the image of the Newtonian world-machine and was to dominate not only the nineteenth century but all future scientific thinking. It involved the idea of evolution; of change, growth, and development. The notion of evolution had arisen in geology, where careful studies of fossils led scientists to the idea that the present state of the earth was the result of a continuous development caused by the action of natural forces over immense periods of time. But geologists were not the only ones who thought in those terms. The theory of the solar system proposed by both Immanuel Kant and Pierre Laplace was based on evolutionary, or developmental, thinking; evolutionary concepts were crucial to the political philosophies of Hegel and Engels; poets and philosophers alike, throughout the nineteenth century, were deeply concerned with the problem of becoming.