Excerpts from The Construction of Modern Science:
Mechanisms & Mechanics (1977)
by Richard S. Westfall
Two dominant themes run through 17th century science. One, which expressed itself through the mechanical philosophy, was the urge to prune all that smacked of the occult from the body of natural philosophy. Drawing inspiration from the atomists of the ancient world, the new conception of nature set about explaining the mechanical reality that must lie behind every phenomenon. No area of science stood immune from its influence. The second theme also traced its history to an ancient source, the Pythagorean sect. Concerned with the exact mathematical description of phenomena, it animated heliocentric astronomy. During the 17th century, the science of mechanics was its principal embodiment.
The history of the modern science of mechanics has consisted of a set of elaborations on the new conception of motion enunciated by Galileo. The first elaboration came from the hands of Descartes. Whereas Galileo had been intent on the problem posed by Copernican astronomy, Descartes focused his attention on the articulation of a new philosophy of nature. Exactly this focus helped him to take a step that Galileo never succeeded in taking, and to treat all motion in the same terms . . . All motions, as motions, were treated in identical terms. All changes of motion were referred to the same cause, the impact of one particle of matter on another . . . Descartes concluded that every body in motion tends always to follow a rectilinear path. It traces a curve only if something diverts it. Since nature is a plenum, every body is in fact continually diverted . . .
In drawing the consequences of his conclusion, Descartes attempted the first analysis of the mechanical elements of circular motion . . .[His] analysis had gross deficiencies, and every beginning student of physics today can do better. Unlike the beginning student today, Descartes had no precedent on which to draw. His analysis furnished the precedent on which others drew and the foundation on which they built—until today the beginning student can quickly be taught to analyze circular motion. Descartes did reach the conclusion that a body moving in a circle constantly strives to recede from the center because of the rectilinear tendency of its motion . . .
Descartes’ natural philosophy also emphasized another problem in mechanics. The conscious exclusion of all that was considered to be occult confined action to the direct contact of one body with another. Hence the problem of impact was bound to assume importance for mechanical philosophers. It was not an easy problem . . . [120-121]
Everyone acknowledges the position of Isaac Newton in the history of science in general and in the history of 17th century science in particular. Not only was Newton’s achievement monumental, so that it stands as one of the supreme accomplishments of the human intellect, but it also drew together the principal strands of 17th century science, solving major problems left unresolved by the scientific revolution. In solving problems, his work did not in any way mark an end or pause for the scientific enterprise. Like all creations of genius, his books opened two new questions for every old one they closed, and if his work summed up the scientific revolution of the 17th century, it also inaugurated 18th century physical science. In Newton, the mechanical philosophyof nature, fundamentally revised, attained a degree of sophistication such that it could furnish the framework of scientific thought in the western world for another two hundred years.
Newton occupies a special position in the history of science for other reasons as well. Since he almost never destroyed a paper—whole stacks of sheets with nothing but raw arithmetical calculations survive—our study of him is not confined to completed and polished works. From his reading he took copious notes which enables us to specify the major influences on him; and through various notebooks which reach back into his undergraduate days, we can trace the steps of his own investigation of nature. The result is a detailed picture, unique in the history of thought, of the progress of a master intellect, a picture which enables us to comprehend Newton’s work as he conceived it and to place it firmly in the context of 17th century science.
That context, inevitably, was the prevailing mechanical philosophy of nature, which fostered the initial steps in scientific thought that Newton took. While he was still an undergraduate, Newton discovered the writings of the mechanical philosophers—Descartes, Gassendi, Hobbes, Boyle, and others. Forthwith, he was converted to their view. In a notebook, he jotted down passages from their works and questions they raised, and he convinced himself of the advantages of the atomist version of the mechanical philosophy . . .
[All] of the crucial phenomena on which Newton speculated throughout his life had one property in common—all of them were problem phenomena difficult to explain by the standard devices of the mechanical philosophy—the shapes, sizes, and motions of particles.
There were bound to be phenomena difficult for the mechanical philosophy, of course. The philosophy was built on the premise that the reality of nature is not identical to the appearances our senses depict . . . microscopic mechanisms were imagined to explain such difficulties away . . .
Newton’s admission of forces acting between particles of matter constituted a major break with the prevailing mechanical philosophy of nature. His treatment of magnetism offers an instructive example of the change. In the 16th century, magnetism was the foremost example of the mysterious influences thought to pervade the universe. Correspondingly, mechanical philosophy had felt compelled to explain magnetic attraction away by inventing an invisible mechanism to account for it. Newton had done the same thing in a youthful writing. In his mature works, magnetic attraction was presented as an example of forces that act at a distance . . . It is small wonder that Newton’s critics felt he was reverting to the style of Renaissance Naturalism and undermining the very foundation on which science rested.
Newton himself considered forces between particles, not as a denial of the mechanical philosophy, but as the conception needed to perfect it. By adding a third category, force, to matter and motion, he sought to reconcile mathematical mechanics to the mechanical philosophy. Force to him was never an obscure qualitative action, as the sympathies and antipathies of Renaissance Naturalism had been. He set it in a precise mechanical context in which force was measured by the quantity of motion it could generate . . . [To Newton] the concept of force represented the means by which the Galilean tradition could be introduced into the mechanical philosophy. And with one force he succeeded in carrying the work to its full and magnificent conclusion. Without the concept of force, the law of universal gravitation was inconceivable. In the law of universal gravitation, the concept of force carried natural science to a new level of sophistication that has stood ever since as the paradigm of a scientific demonstration. . . .
What is force? In the context of the prevailing mechanical philosophy, it could mean only one thing: “Force is the pressure or crowding of one body upon another.” With the statement neither Descartes nor Gassendi nor Boyle would have disagreed. Nevertheless, Newton was posing a question they had not put. Descartes . . .had spoken of the “force of a body’s motion.” On the other hand, Newton was thinking in terms of an abstract quantity which could measure the change in the motion of a moving body . . . .
Newton believed that nature is ultimately opaque to human understanding. Science cannot hope to obtain certain knowledge about the essences of things. Such had been the program of the mechanical philosophy in the 17th century, and the constant urge to imagine invisible mechanisms sprang from the conviction that a scientific explanation is only valid when it traces phenomena to ultimate entities. To Newton, in contrast, nature was a given, aspects of which might never be intelligible . . . Newton believed that the aim of physics is an exact description of phenomena of motion in quantitative terms. Thus the concept of force could be admitted into scientific demonstrations even if the ultimate reality of force were not comprehended. In Newton’s work, it made possible the reconciliation of the tradition of mathematical description, represented by Galileo, with the tradition of mechanical philosophy, represented by Descartes. By uniting the two, Newton carried the scientific work of the 17th century to that plane of achievement which had led historians to speak of a scientific revolution. . . [139-159]
1)What are the major points made about Newton in these excerpts?
2)How did Newton see further by “standing on the shoulders of giants”? Who were these giants and how did Newton’s work build upon their work? Be specific.