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|SummaryBrief='''Sir Isaac Newton''' (1642-1727) was a an English mathematician, astronomer, and physicist/natural philosopher who lived and worked in England in is widely recognized as one of the 17th and 18th century. 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)|The Principia]] (''Philosophiæ Naturalis Principia Mathematica'']]), whose principles became central to be the foundation for the dominant Newtonian mosaic which influenced much of late 18th and 19th century science.[[CiteRef::Janiak (2016)]] Some consider The 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 his 1543 ''De revolutionibus orbium coelestium'' (''On the Revolutions of Heavenly Spheres''). It had been fifty years since Galileo Galilei (1564-1642) had published his observations with the telescope in 1610. Galileo had discovered , which uncovered dramatic evidence favoring for the Copernican system. His discovery of the phases of the planet Venus indicated that it revolved around the sun and was lit by reflected sunlight. His description of four moons circling Jupiter indicated that Earth, with its own moon, resembled this planet. His studies of sunspots indicated that the sun revolved on its axis, and finally, his discovery of surface features on the moon indicated that the moon was another world, as expected under the Copernican system, but not by Aristotelianism. Around At about the same time, Johannes Kepler (1571-1630)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 Aristotelian physicsof [[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 can could hope to gain reliable knowledge given in the face of the evident 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]] the curriculum had changed little in decades, despite the incompatibility of Aristotelian natural philosophy with Copernican heliocentrism.[[CiteRef::Westfall (1980)|pp. 81-90]][[CiteRef::Smith (2009)]] Like many of the more ambitious students, Newton is known to have 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 philosophicaPhilosophica'', 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 priorearlier, and these 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)]]

Both Newton’s physics and philosophy were heavily influenced by Descartes’ ideas though they were also a challenge to what had, by then, become the new Cartesian orthodoxy. Descartes' '''mechanical natural philosophy''' was derived from ancient Greek atomism. He 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. Particles 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)]] Aristotle had explained the properties of visible bodies in terms of their form, rather than in terms One of the arrangement attractions of their constituent parts. He maintained these ideas is that heavy objects, composed of the element earth, tended towards their natural place; the center of the universe. The concept of a sphere of earth at rest in the center of the universe was central to unlike Aristotle's entire cosmology. Motion in the terrestrial , they allowed for a movable planetary Earth, and celestial realms were seen as fundamentally motions weren't differentin kind from terrestrial motions.[[CiteRef::Bodnar (2016)]] Descartes' theories They explained gravity , in qualitative terms, as due to a swirling vortex of particles around the Earth, which pushed things towards its center. Celestial motions were not different in kindcentre. 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. By the time Newton published his magnum opus, ''Philosophiae Naturalis Principia Mathematica'' (''Mathematical Principles of Natural Philosophy'')in 1687, Descartes' views had been accepted at Cambridge. The 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)]] Newton contested Cartesianism as the orthodoxy he sought to overturn.

For Descartes saw , the ultimate justification of knowledge claims to 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 by Gottfried Wilhelm Leibniz.[[CiteRef::Lennon and Dea (2014)]] But, by the early 17th century, experimental researchers like Galileo Galilei 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 their that most experimental work involved formulating hypotheses about unobservable entities, which were tested by their observable consequences. Newton rejected Cartesian rationalism, and argued that the Cartesians did not sufficiently employ mathematics and experimentation in their work. He rejected and the method This was an early form of hypotheses outright. [[CiteRef::McMullin (2001)]][[CiteRef::Janiak (2016)]] He supported inductivism, and held epistemological views similar to those of his contemporary and friend [[John Locke]](1632'''hypothetico-1704), who maintained that all knowledge came from experiencedeductivism'''.[[CiteRef::Rogers (1982)]]|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 ===Whereas Descartes did not rely on mathematical reasoning for his deductions of scientific propositions, Newton believed that mathematics was an imperative part 's two most important works of conducting natural philosophy.were the ''Principia'', published in 1687 [[CiteRef::Janiak Newton (20161687)]] In Newton’s physics, material objects were not required to be in direct contact which dealt with each other in order for his theories of motion to occur. Insteadand universal gravitation, objects react to each other via a force, a new concept which Newton envisioned as a quantifiable property contained in all material objectsand ''Opticks: or, the amount A Treatise of which is directly proportional to the quantity of matter contained in the object. Quantities of force Reflexions, Refractions, Inflexions, and matter were thus introduced to the mosaic as ontological entities that were measurable. By applying Newton’s three laws Colours of motion, material objects Light'' [[CiteRef::Newton (1704)]] which was published in the universe were compelled to accelerate through action at a distance. Additionally, the laws outlined the mathematical relations between this acceleration 1704 and the quantities dealt with his theories of force light and matter could be explained and predicted mathematically, thereby giving color. [[CiteRef::Westfall (1999)]] Newton made mathematics a new much more central role in to the study conduct of natural philosophy. In The ''Principia''than Descartes, Newton made extensive use by producing a general mathematical theory of mathematics in his argument for the unified theory motion of gravitybodies.[[CiteRef::Smith Janiak (20092016)]] The He posited three mathematical language used in The ''Principia'laws of motion''' was geometry, which was also together with a '''law of universal gravitation'''. Changes in the basis for many 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 major models for celestial mechanics that were studied at mathematical relationship between the timeacceleration experienced by an object, including the works quantity of Ptolemymatter composing it, Copernicus and Keplerthe magnitude of the forces acting on it.[[CiteRef::Smith (2009)]]

Even though Newton published his key work In contrast with the Cartesian mechanical philosophy, in the language of geometryNewton’s physics, as material objects were not required to be in direct contact in order to influence each other's motion. Forces could act at a mathematician he is primarily role in inventing integral distance. To explain both falling bodies on Earth and differential calculus. He is co-credited independently for the calculus alongside his contemporary motions of the moon and rival natural philosopherplanets, LeibnizNewton posited a '''gravitational force''' that acted as the inverse square of the distance between objects.[[CiteRef::Cohen and Smith (EdsHe claimed to have derived this relationship from Kepler's observational laws of planetary motion.) (2002)|pp. 13-14]] As a mathematical techniqueThe works of Ptolemy, Copernicus, calculus had been and Kepler used the first method that was capable mathematical language of geometry in their descriptive accounts of articulating celestial motions. In the quantity ''Principia'' Newton likewise presented his arguments geometrically. Unlike his predecessors, Newton sought to do more than simply describe celestial motions. He sought to explain them in terms of accelerationgravitational forces acting between bodies. In order to do this, unlocking Newton invented a new world branch of calculations which geometry mathematics, '''integral and differential calculus'''. Calculus deals with mathematical quantities that are continuously changing, such as a technique had been incapable the magnitude and direction of solvinggravitational forces acting on an orbiting body.[[CiteRef::Friedman (2002)]] Eventually, 18th century that mathematicians Jacob Hermann and Leonhard Euler expressed Newton’s laws of motion using Newton's own technique of calculus, but in the symbolic expression that Leibniz had developed.[[CiteRef::Smith (2009)|p. 29]] In following yearsNewton developed the basic concept of calculus during 1665-6, calculus became indispensable tool for scientists in the Newtonian mosaic while Cambridge University was closed due to solve problems in physicsa plague, and to predict but didn't publish it until the behaviour first decade of material objects the eighteenth century. He is thus co-credited with inventing calculus with an unprecedented degree of accuracyhis contemporary and rival Gottfried Wilhelm Leibniz (1646-1716).[[CiteRef::Cohen and Smith (2009Eds.) (2002)|pp. 10-20]] Although geometry is still taught in schools today, calculus is the primary mathematical technique learned and used in physics and engineering classrooms.

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. The were often deduced Cartesian '''rationalism'''sought to deduce such hypotheses from fundamental metaphysical principles that were deemed evidently true by human reason . [[CiteRef::Janiak (20142016)]][[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 (20142016)]][[CiteRef::Smith (2002)]]. In the second edition of The the ''Principia'', Newton states:

The generality of Newton's rejection of hypotheses in natural philosophy is unclear since, in the ''Opticks'' he did discuss hypotheses about light, and did raise the possibility of an invisible aether responsible for gravitational attraction. [[CiteRef::Janiak (2016)|pp. 25-26]] His epistemological beliefs were similar to those of his contemporary and friend, [[John Locke]] (1632-1704) who maintained that all knowledge came from experience. [[CiteRef::Rogers (1982)]] Newton called his method methodology the '''experimental philosophy''', because theories about the behavior of empirical objects can only be refuted via experimental procedures.[[CiteRef::Smith (2002)]] He expressed the its core beliefs from which he derived his method in a set of four “rules for the study of natural philosophy,” which he stated in book III of The ''Principia'' as follows:

Out of these four rules a new, engaged method for conducting science emerged that stood in stark contrast to the previous passive and theoretical Cartesian and Aristotelian-scholastic methods. Propositions are born from formulated based on observations of the natural sources world and placed back into the natural world to be tested empirically.[[CiteRef::Smith (2002)]] As the four rules were absorbed into the ensuing mosaic, the The calculus became deeply incorporated in into the experimental method, as it was used to mathematically calculate empirical predictions from natural laws, and then evaluate how exactly the prediction matched the observed reality.Newton claimed to have derived his law of universal gravitation using this method as applied to Kepler's laws of planetary motion. In the Cartesian natural philosophy, centripetal force had already been defined as the agent that pulled the moon towards the Earth, keeping its orbit circular rather than linear. Newton appealed to rules 1) and 2) to claim that the centripetal force, and the force that compelled objects to move downwards towards the Earth, were merely two different expressions of the same thing. Newton then went on to apply the third rule, and argue that this force, which he called gravity, must be a universal property of all material objects. From here, he went on to argue for the unification of superlunary and sublunary phenomena, which Aristotle had deemed to be distinct realms.[[CiteRef::Harper (2002)|pp. 183-184]]|Criticism=Newton's theories provoked immediate and wide interest in Britain, and became accepted there by the first decade of the eighteenth century. [[CiteRef::Smith (2009)]][[CiteRef::Barseghyan (2015)|p. 210]] In continental Europe, acceptance came more slowly. To proponents of the mechanical philosophy, it was methodologically necessary that all motion be given a cause involving direct physical contact of bodies. Many of Newton's continental contemporaries, in particular Leibniz and Huygens, strongly objected to the idea that forces could act at a distance. Leibniz regarded the theory of gravitation as a regression in natural philosophy and accused Newton of treating gravity as an 'occult quality' beyond philosophical understanding. After an intense debate, Newtonian gravitation theory became accepted through much of continental Europe by the middle of the eighteenth century. [[CiteRef::Janiak (2016)]] [[CiteRef::Barseghyan (2015)|pp. 211-212]][[CiteRef::Aiton (1958)|p. 172]][[CiteRef::Frangsmyr (1974)|p. 35]]

Using these principles, More than two centuries after Newton was able to derive published the law ''Principia'', a new theory of universal gravity motion and gravitation was formulated by Albert Einstein (1879-1955), who was inspired by new developments in non-Euclidean geometry and by problems with James Clerk Maxwell's (1831-1879) theory of electromagnetic radiation. The new theory replaced Newton's theory as the context accepted theory of his methodmotion and gravitation by about 1920. In Einstein's '''General Theory of Relativity''' explained the Cartesian mosaic, the centripetal force had already been defined as the agent success of its predecessor by showing that pulled the moon towards the Earth, keeping its orbit circular rather than linear. equations reduce to those of Newton applied rules 1) in the limit of weak gravitational fields and 2) to determine velocities that are an insignificant fraction of that of light. Einstein's theory eliminated the centripetal force, and the force problem of action at a distance by postulating that compelled objects to move downwards towards the Earth, were merely two different expressions mass of the same thing. Newton then went on to apply the third rulean object warps space-time, and argue that this force, which he called gravity, must be a universal property of all material objects. From here, he went on to argue for the unification local manifestation of superlunary and sublunary phenomenathis curvature influences distant bodies.[[CiteRef::Harper Barseghyan (20022015)|ppp. 183-184125]][[CiteRef::Isaacson (2007)]]

Although not all of the ontological changes to the mosaic described in The Newton''Principia'' were immediately s experimental philosophy shaped acceptedclaims about scientific methodology, influencing the new experimental philosophy that he described influenced contemporary scientists within the same century methodological pronouncements of it’s publicationGeorge Berkeley (1685-1753), David Hume, Thomas Reid (1710-1796), and Immanuel Kant (1724-1804). [Newtons philosophy[CiteRef::McMullin (2001)]] Both prominent 17th century natural philosophers Christiaan Huygens and John Locke are known However, according to have taken the experimental philosophyMcMullin, if not necessarily Newton's methodology ran contrary to the full content consensus that had been emerging among natural philosophers of Newton’s theorieshis time, to heartin favor of what we now recognize as the '''hypothetico-deductive method'''.[[CiteRef::Janiak McMullin (20162001)]] By 1700 Historical research shows that the scientific community did not use Newton's own criteria in evaluating his work. His theories did not become accepted outside of England until after their prediction of the acceptance oblate spheroid shape of “experimental philosophy” methodological structure had overtaken the Earth was confirmed by expeditions to Lapland and Peru. Newton's own theories became accepted based on confirmed novel predictions that distinguished them from the rival theory of Cartesianism Cartesian vortices, rather than by Newton's own '''inductive methodology'''. Further, Newton's theory, in Englandfact, posited unobservable hypothetical entities, including gravitational attraction, absolute space, and absolute time.[[CiteRef::Barseghyan (2015)|p.48-49]][[CiteRef::Janiak Terrall (20161992)]][[CiteRef::McMullin (2001)]]|Criticism=Although many By the mid-eighteenth century natural philosophers in were beginning to realize that many successful theories violated the 17th strictures of Newton's inductive experimental philosophy. The eighteenth century were convinced by Newton’s views on saw the acceptance of a variety of theories that posited unobservable entities, including Benjamin Franklin's (1706-1790) theory of electricity, which posited the proper method existence of conducting sciencean unobservable electric fluid, many were not willing to abandon the Cartesian mechanical philosophy. Contemporary philosopher Leibniz in particular was concerned that the phlogiston theory of gravity as a regression in natural philosophycombustion and rust, which likewise posited an unobservable substance, and Augustin-Jean Fresnel's (1788-1827) wave theory of light which posited an unobservable fluid ether as Newton could not account for the source medium of gravitylight, and Herman Boerhaave's (1668-1738) vibratory theory of heat. [[CiteRef::Laudan (1984a)|pp. 56-57]][[CiteRef::Barseghyan (2015)|p. To 54]] The methodologists of the Cartesiansearly nineteenth century, it was more important William Whewell (1794-1866) and John Hershel (1792-1871) recognized that all motion in the universe could be given a direct cause, which was only possible under actual practice of science did not conform to the mechanical philosophy, even if this amounted to a larger gap between theory prescribed Newtonian methodology and experimental evidenceopenly advocated the hypothetico-deductive method.[[CiteRef::Janiak Laudan (20161984a)|pp. 56-60]]

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