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|Brief=an English mathematician, astronomer, and physicist/natural philosopher who is widely recognized as one of the most influential scientists of all time
|Summary=Newton’s most notable contributions were made to the fields of physics, mathematics, and scientific method, which were so groundbreaking that he is currently considered to be one of the most important physicists in modern Western history.[[CiteRef::Janiak (2016)]] Philosophers of science credit Newton’s revolutionary theory of gravity and his experimental approach to conducting natural philosophy as outlined in his major work, ''Philosophiæ Naturalis Principia Mathematica'' (''Mathematical Principles of Natural Philosophy'' or simply the [[Newton (1687)|''Principia'']]), whose principles became central to the mosaic of late 18th and 19th century science.[[CiteRef::Janiak (2016)]] Some consider the ''Principia'' to be the work that initially created physics as its own scientific field separate from the umbrella of metaphysics and philosophy. [[CiteRef::Janiak (2016)]]
|Historical Context=When Isaac Newton began his studies at Cambridge University's prestigious Trinity College in 1661, more than a century had passed since Nicolaus Copernicus (1473-1543) had proposed a '''heliocentric cosmology''' in 1543. It had been fifty years since Galileo Galilei (1564-1642) had published his observations with the telescope in 1610, which uncovered dramatic evidence favoring for the Copernican system. At about the same time, Johannes Kepler (1571-1630) had published his laws of planetary motion, indicating that the planets revolved around the sun on elliptical paths, replacing the circular motion and complex epicycles of Copernicus and Claudius Ptolemy (c. 100-170).[[CiteRef::Westfall (1980)|pp. 1-7]] According to Westfall, "by 1661 the debate on the heliocentric universe had been settled; those who mattered had surrendered to the irresistible elegance of Kepler's unencumbered ellipses, supported by the striking testimony of the telescope, whatever the ambiguities might be. For Newton, the heliocentric universe was never a matter in question".[[CiteRef::Westfall (1980)|p. 6]] A planetary Earth that rotated on its axis and revolved around the sun was incompatible with the accepted physics of [[Aristotle]] (384-322 BCE). The community of the time was engaged with the question of how it could be that the Earth itself was in motion through space, and with the question of how one could hope to gain reliable knowledge in the face of the failure of Aristotelian scholastic knowledge accepted for centuries.
Newton’s education at Cambridge was classical, focusing on Aristotelian rhetoric, logic, ethics, and physics. Bound to '''Aristotelian scholasticism''' by statutory rules,the curriculum had changed little in decades.[[CiteRef::Christianson (1984)|p. 33]][[CiteRef::Westfall (1980)|pp. 81-90]][[CiteRef::Smith (2009)]] Like many of the more ambitious students, Newton distanced himself from classical metaphysics and instead studied the works of the French natural philosopher [[René Descartes]](1596-1650) on his own. By 1664, Newton is known to have read the 1656 Latin edition of Descartes' ''Opera Philosophica'', a one volume compilation of Descartes' major works.[[CiteRef::Smith (2009)]] Newton is known to have been profoundly influenced by Descartes views of space, matter, and God, and by commentaries on Descartes by Henry More (1614-1687). [[CiteRef::Janiak (2016)]] Descartes had died just over a decade earlier, and his works had first been published within the preceding thirty years. They were gaining in popularity and by about 1680 would become the [[Theory Acceptance|accepted]] centerpiece of the Cambridge curriculum, as they also would in Paris by 1700.[[CiteRef::Barseghyan (2015)|p. 190]] When Newton published his magnum opus, the ''Principia'' in 1687, he was challenging a Cartesian orthodoxy. The full title of Newton's work suggests he intended it to be in dialog with Descartes' ''Principia Philosophiae'' (''Principles of Philosophy'') published in 1644.[[CiteRef::Janiak (2016)]]
Descartes was the most prominent member of a community of '''corpuscularist''' thinkers, who maintained that visible objects were made of unobservably tiny particles, whose relations and arrangement were responsible for the properties of visible bodies. In this '''mechanical natural philosophy''', particles influenced one another only by direct physical contact, which was the cause of all motion, and ultimately all change.[[CiteRef::Disalle (2004)]] One of the attractions of these ideas is that, unlike Aristotle's, they allowed for a movable planetary Earth, and celestial motions weren't different in kind from terrestrial motions. They explained gravity, in qualitative terms, as due to a swirling vortex of particles around the Earth, which pushed things towards its centercentre. In accord with Copernican heliocentrism, Descartes posited that a larger vortex surrounded the sun, with the smaller planetary vorticies caught in a larger solar vortex.[[CiteRef::Garber (1992)]][[CiteRef::Disalle (2004)]] In Newton's time, major champions of the mechanical natural philosophy included Christiaan Huygens (1629-1695) and Gottfried Wilhelm Leibniz (1646-1716), who was to become a major rival of Newton's.
For Descartes, the ultimate justification of knowledge claims lie with human reason and the absence of doubt. He relied on classical methods of theorizing and conjectured hypotheses in order to construct scientific propositions.[[CiteRef::Janiak (2016)]] Such a '''rationalist''' approach to knowledge was also championed by Baruch Spinoza (1632-1677), Nicolas Malebranche (1638-1715), and Leibniz.[[CiteRef::Lennon and Dea (2014)]] But, by the early 17th century, experimental researchers like Galileo and Robert Boyle (1627-1691) had begun to elaborate and practice a very different approach to knowledge based on experimentation and extensive use of mathematics. Following the '''inductive methodology''' advocated by [[Francis Bacon]](1561-1626), they maintained that theoretical principles emerged from experimental data by a process of inductive generalization. However, there were also dissenters like Newton's contemporary Christiaan Huygens, who believed that most experimental work involved formulating hypotheses about unobservable entities, which were tested by their observable consequences. This was an early form of '''hypothetico-deductivism'''.
|Major Contributions={{#evt:service=youtube|id=ELbm5KUYMLM|alignment=right|description=Hakob Barseghyan's lecture on Newtonian Worldview|container=frame }}=== Newton on Mathematics and Natural Philosophy ===
Newton's two most important works of natural philosophy were the ''Principia'', published in 1687 [[CiteRef::Newton (1687)]], which dealt with his theories of motion and universal gravitation, and ''Opticks: or, A Treatise of the Reflexions, Refractions, Inflexions, and Colours of Light'' [[CiteRef::Newton (1704)]] which was published in 1704 and dealt with his theories of light and color. [[CiteRef::Westfall (1999)]] Newton made mathematics much more central to the conduct of natural philosophy than Descartes, by producing a general mathematical theory of the motion of bodies. [[CiteRef::Janiak (2016)]] He posited three mathematical '''laws of motion''', together with a '''law of universal gravitation'''. Changes in the state of motion of objects were caused by '''forces''' acting on them. Quantities of force and amounts of matter were measurable. The laws specified the mathematical relationship between the acceleration experienced by an object, the quantity of matter composing it, and the magnitude of the forces acting on it. [[CiteRef::Smith (2009)]]
=== Newton on Methodology ===
Prior to the publication of The ''Principia'', the philosophy of motion and change in the universe was largely a theoretical and non-mathematical enterprise. The dominating methodological approach both in the Aristotelian-scholastic and Cartesian natural philosophy, was one in which truths about the natural world were proposed as conjectural hypotheses. Cartesian '''rationalism'''sought to deduce such hypotheses from fundamental metaphysical principles that were deemed evidently true by human reason. [[CiteRef::Janiak (2016)]][[CiteRef::Lennon and Dea (2014)]] Influenced by the more experimental and mathematically oriented methodologies of Bacon, Galileo, and Boyle, Newton drew a distinction between a conclusion drawn from observation or experimental evidence and one that was merely a speculative 'hypothesis'. He explicitly rejected the method of hypotheses, and instead demanded that all propositions be deduced from the observed phenomena and then converted into general principles via '''induction'''. [[CiteRef::McMullin (2001)]][[CiteRef::Janiak (2016)]][[CiteRef::Smith (2002)]] In the second edition of the ''Principia'', Newton states:
<blockquote>I have not as yet been able to deduce from phenomena the reason for these properties of gravity, and I do not feign hypotheses. For whatever is not deduced from the phenomena must be called a hypothesis; and hypotheses, whether metaphysical or physical, or based on occult qualities, or mechanical, have no place in experimental philosophy. In this experimental philosophy, propositions are deduced from the phenomena and are made general by induction. The impenetrability, mobility, and impetus of bodies and the laws of motion and law of gravity have been found by this method. And it is enough that gravity should really exist and should act according to the laws that we have set forth and should suffice for all the motions of the heavenly bodies and of our sea.[[CiteRef::Newton (1999)| p. 276]]</blockquote>
|Related Topics=Methodology,
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