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|First Name=ReneRené

|SummaryBrief=[[File:Descartes.jpg|right|400px]]'''Rene Descartes''' (1596-1650) was a French mathematician and natural philosopher. ; who is today considered one of the most influential figures in modern philosophy|Summary=Descartes rejected the Aristotelian-scholastic world view medieval mosaic accepted for most of the previous two thousand years, and laid down the foundations of a new foundations for knowledgemechanistic mosaic.[[CiteRef::Russell (1945)|p. 524]][[CiteRef::Newman (2014)]][[CiteRef::Garber (1993)]] Aristotelians had maintained that intuition schooled by experience was the route to knowledge. Descartes, in his ''Discourse on the Method of Rightly Conducting One’s Reason and of Seeking Truth in the Sciences'' (''Discourse on Method''), first published in 1637,[[CiteRef::Descartes (2007)]] put forward a rationalist scientific methodology in which a proposition is acceptable only if it can be clearly and distinctly perceived by the intellect beyond all reasonable doubt or follows deductively from such propositions.[[CiteRef::Newman (2014)]] This allowed him to advance a mathematical a priorist approach to scientific knowledge and inquiry.[[CiteRef::Garber (1992)]][[CiteRef::Clarke (1992)]] Rejecting the Aristotelian world of forms, substances, and teleology, he posited a mechanical world in which matter possessed only spatial extension and interacted only by contact. In mathematics he developed techniques that made possible analytic geometry. In natural philosophy, he was co-framer of the sine law of light refraction, developed a theory of the rainbow, and formulated a precursor of the nebular hypothesis of the origin of the solar system.[[CiteRef::Hatfield (2016)]]|Historical Context=[[File:La Fleche College.jpg|right|400px]]The [[Scientific Mosaic|scientific mosaic]]of the late sixteenth and early seventeenth centuries was based primarily on the works of [[Aristotle ]] and some later Hellenistic natural philosophers, . This was reconciled in various ways with Christian theology by scholars in the High Middle Ages. This '''Aristotelian-scholastic mosaic''' included Christian theologyPtolemaic astronomy, astrology, humoral physiology, astrology, Ptolemaic astronomy, and Christian (Catholic, in many but not all communities contemporaneous with Descartes) theology.[[CiteRef::Haldane (1905)]] Descartes was well educated in this tradition through his attendance at the prestigious Jesuit La Fleche College between the ages of ten and eighteen. He studied a traditional scholastic curriculum of logic, grammar, philosophy, mathematics, and theology. Natural philosophy was taught from the works of Aristotle as interpreted by Christian scholars. Descartes also received an education in mathematics that was unusual for the Aristotelian tradition, and excelled at math. [[CiteRef::Gaukroger (1995)|pp. 38-61]][[CiteRef::Rodis-Lewis (1992)]][[CiteRef::Garber (1992)]]

Descartes’ major writings came in a time of social and intellectual upheaval in Europe. He Before writing his major works, he was a participant in the Thirty Years War before writing his major works and traveled . He travelled extensively around Europe at a time when the continent was embroiled in both reformation and counter-reformation, both of which were both a wellspring of new thought in theology and philosophy. The community of the time was engaged with major challenges to the Aristotelian-scholastic tradition. These came from a variety of varied sources, including various varieties of Platonism, Hermeticism, and the Chemical Philosophy chemical philosophy of Paracelsus, among other movements.[[CiteRef::Garber (1992)]] There were new developments in optics, astronomy, and physiology.[[CiteRef::Cottingham (1992)]] Aristotle's earth-centered cosmology had been challenged by the work of Nicolaus Copernicus(1473-1543), Johannes Kepler(1571-1630), and Galileo Galilei(1564-1642), which Descartes was familiar with.[[CiteRef::Hatfield (2016)]][[CiteRef::Rodis-Lewis (1992)]][[CiteRef::Ariew (1986)]]

The After leaving La Fleche, in 1618,Descartes became involved in a collaboration with the Dutch Calvinist natural philosopher Isaac Beeckman (1588-1687), who valued him for his mathematical skills. They worked together on several mathematical problems in natural philosophy. [[CiteRef::Gaukroger (1995)|p. 68]] Beeckman was a supporter of the '''mechanical natural philosophy''' . This was a [[Theory Pursuit|pursued]] radical alternative to Aristotelian cosmology, embraced by some supporters of Copernican heliocentrism.[[CiteRef::Luthy, Murdoch, and Newman (2001b)]][[CiteRef::Chalmers (2014)]][[CiteRef::Gaukroger (1995)|p. 69-73]] It rejected the Aristotelian fundamentals of form, substance, and teleology, and the idea that matter is continuous. Instead of explaining the properties of visible bodies in terms of form, it instead maintained that the world consisted of invisibly tiny particles of matter and that all the observable properties of the visible bodies were a consequence of these particles and their interactions with one another. The particles interacted were held to interact mechanically, by contact, and it was often supposed that they this rendered natural phenomena potentially explainable in geometrical and mathematical terms. Unlike Aristotle's physics, it was compatible with a moving planetary Earth. It can be traced to the Ancient Greek '''atomism''' of Democritus (circa 460-370 BCE) and later Epicurean philosophers. Atomism was reintroduced into European thought in the fifteenth century with the rediscovery of the Roman poet Lucretius's ''De rerum natura''. Part of its appeal lay in the fact that unlike Aristotle's physics, the mechanical philosophy was compatible with a moving planetary Earth. In the early seventeenth century, it was championed by Giordano Bruno (1548-1600), Nicolas Hill (1570-1610?), Sebastian Basso (1573-1625?), Francis Bacon (1561-1626), and Galileo Galilei.[[CiteRef::Garber (1992)]][[CiteRef::Klein (2012)]][[CiteRef::Gatti (2001)]][[CiteRef::Luthy, Murdoch, and Newman (2001b)]]

After leaving La Fleche, in 1618,Descartes became involved in a collaboration with the Dutch Calvinist natural philosopher Isaac and Beeckman (1588-1687), who valued him for his mathematical skills. They worked together on several mathematical problems in natural philosophy. Beeckman was a corpuscularist. A derivative of atomism, '''corpuscularism''' rejected indivisible atoms and void spaces but nonetheless accounted for the properties of objects in terms of invisibly tiny particles [[CiteRef::Gaukroger (1995)|p. 68]] He is almost certainly the first person in Europe to attempt to explain macro-geometrical regularities in terms of micro-mechanical models. [[CiteRef::Gaukroger (1995)|p. 70]] For the most part, applying mathematics to physical problems was not part of the Aristotelian tradition. Descartes adopted Beeckman's mathematical corpuscularism and became part of a community of corpuscularist thinkers which besides Beeckman and Descartes included Marin Mersenne (1588-1648), Thomas Hobbes (1588-1679), Pierre Gassendi (1592-1655), Sir Kenelm Digby (1603-1665), and Walter Charleston (1620-1707). They all knew each other and reacted to each other's work.[[CiteRef::Osler (2001)]] The decade after Descartes met Beeckman was the most philosophically productive of his life. [[CiteRef::Garber (1992)]]

|Major Contributions=Descartes new methodology and mechanical natural philosophy were of revolutionary importance. They became accepted at Cambridge University in England by 1680,[[CiteRef::Barseghyan (2015)|p. 211]] and in France by about 1700, displacing the Aristotelian-medieval system of theories that had been central elements of the [[Scientific Mosaic|scientific mosaic]] for centuries. These theories were ultimately fully displaced throughout Europe by Descartes' theories and by the later theories of Issac [[Isaac Newton ]] (1642-1726).[[CiteRef::Barseghyan (2015)|p. 167]]

[[File:Evil demon t shirt.jpg|right|300px]]Under the Aristotelian scholastic [[Methodology|methodology]] a theory is acceptable “if it grasps the nature of a thing through intuition schooled by experience, or if it is deduced from general intuitive principles”.[[CiteRef::Barseghyan (2015)|p. 144]] Descartes became frustrated with this tradition and its dialectical approach to knowledge-seeking, which he charged with plunging him into skeptical doubts whereby he could never be sure what was true and what was not. He writes in ''Discourse on the Method'':[[CiteRef::Descartes (2007)]]

Descartes concluded that if his goal was to attain certain knowledge about the world,the accepted methodology for doing so must be rejected, and a new one would be requiredformulated. Methodology held a central place in his epistemology; in fact, one of Descartes’ criticisms of Galileo was that he failed to produce a fully developed methodology to justify his discoveries, and had simply explained particular physical phenomena.[[CiteRef::Ariew (1986)]] Rather than experience and intuition, Descartes ' '''methodological skepticism''' was based on reason and on the capacity to doubt. The harder a proposition was to doubt, the greater its certainty. This was an epistemological innovation.

His strategy was, first, to reject all knowledge that he cannot be certain of, and accept only those propositions of which he is certain. He would deduce other knowledge from such axioms using reason. By this method Descartes hoped to produce a kind of systematized knowledge that could be universally accepted. In his ''Meditations on First Philosophy'', [[CiteRef::Descartes (2004)]] Descartes identified the sole indubitable proposition upon which he would build his entire philosophical system: he was certain of his own existence as a thinking being, or in latinLatin, '''''‘Cogito, Ergo Sum’''''' (also styled ''‘Dubito, Ergo Cogito, Ergo Sum’ '' or simply as ''‘the Cogito’''); “I think, therefore I am.” From the foundation of his own existence, Descartes deduced that he must be a created being, that this requires a creator, that creator being God, the benevolent nature of God, and the consequent reliability of his senses and of the God-given ability of his reason to form clear and distinct ideas. It was therefore possible to use his senses and reason to gain knowledge of an external world. This reasoning formed the foundation of his systematized scientific worldview.[[CiteRef::Newman (2014)]]

Descartes maintained some aspects of the Scholastic-Aristotelian methodology – namely an axiomatic-deductive, epistemic-foundationalist structure of investigation. But the critical difference in his methodology was the shift in the method of theory choice. It He jettisoned the Aristotelian expectation that a theory must be experientially based and intuitively obvious for it to be acceptable, and although his system, as it ended up, allowed for knowledge that was both experiential and intuited,[[CiteRef::Newman (2014)]] the ultimate justification for knowledge claims was human reason and the absence of doubt. Descartes was both a '''rationalist''' and an '''a priorist''', in that his epistemology and metaphysics allows for the existence of synthetic a priori propositions. Although an argument for God's existence was at the foundation of his system, Descartes' rationalism was nonetheless a formidable challenge to the accepted theological methodology which had been comprehensively expressed by the Catholic saint, Thomas Aquinas (1225-1274) more than three hundred years earlier. Aquinas saw human reason as limited, and always to be exercised in the context of, and subject to the authority of, the divine revelation of the Bible. Descartes, by contrast, sought to develop his epistemology and theology on the basis of human reason alone. [[CiteRef:: Hyman (2007)]]

Descartes also challenged Aristotelian physiology. Aristotle's theory of physiology posited three souls or vital principles; the nutritive soul, responsible for nutrition and reproduction, comprised the entirety of the soul in plants. The sensitive soul, responsible for perception, locomotion, imagination, and desire, was added to the sensitive soul in animals. A third component, the intellectual soul, was found uniquely in human beings. [[CiteRef::Shields (2016b)]][[CiteRef::Van der Eijk (2000)]] Descartes rejected the nutritive and sensitive souls, supposing their functions were instead performed by corpuscular mechanisms, the nature of which he outlined in his ''Treatise on Man''. [[CiteRef::Descartes (2007)]] Descartes' mental substance served roughly the same role as Aristotle's intellectual soul. Animals, according to Descartes, are complex automata composed of physical substance only and cannot be said to think in the way that human beings or God can; these properties being made possible by mental substance. [[CiteRef::Des Chene (2001)]][[CiteRef::Clarke (1992)]][[CiteRef::Descartes (2007)]] Descartes posited a mental substance for theological, metaphysical, and scientific reasons. He supposed that thought could not be mechanized, since all the machines known to him were specialized to perform one particular function, but human reason was a general purpose instrument.[[CiteRef::Hatfield (1992)]][[CiteRef::Cottingham (1992)]] Descartes mechanical natural philosophy fostered a radical change in how natural philosophers gained new knowledge. The Aristotelian-medieval methodology accorded a very limited role for experiments in scientific investigation. This is because a strict distinction was made between natural and artificial things. Every natural thing behaved in accordance with its nature; acorns grow on oak trees, because that is what their nature dictates. Artificial things have an external source of change. The cogs and springs of a clock are constructed so that they no longer behave according to their respective natures (which is simply to fall towards their natural place at the center of the universe, rather than function as parts of a machine that tells time for humans). A thing cannot reveal its true nature under the artificial conditions of experimentation, because the experimental set up necessarily puts things under artificial conditions. To gain knowledge, things must be observed in their natural undisturbed state. Descartes' mechanical natural philosophy rejected the natural/artificial distinction along with its rejection of forms and teleology. Matter always obeyed the same set of mechanical laws regardless of its situation. Thus,under the mechanical natural philosophy experimentation was often a good source of knowledge about nature, and its adherents often became practitioners. [[CiteRef::Barseghyan (2015)|p.181-182]]

The overthrow of challenge to the Aristotelian tradition, even in places where Cartesianism was rejected and the community maintained Aristotelianism, forced the academic community in Europe to reconsider and defend the Aristotelian mosaic in ways that had never before been encountered. Though the dialectical approach to scholarship throughout the medieval period saw scholars constantly questioning various aspects of the Aristotelian worldview, Descartes’ wholesale rejection of huge swaths of the mosaic and its central concepts were unprecedented. Theories like hylomorphism(that being is a compound of matter and form), which had been a given in the mosaic of the sixteenth and early seventeenth centuries, and had endured through multitudes of adjustments, reconciliations, and dialectic criticism, but had never before faced complete overhaul that Descartes's mechanical natural philosophy threatened. Although Descartes' theories would eventually be supplanted by those of Newton, he made the critical first steps to replacing the Aristotelian-scholastic mosaic.[[CiteRef::Hatfield (2016)]]|Criticism=Descartes’ ideas saw widespread criticism in his time and shortly after from all manner of sources, including Scholastic vanguards, religious authorities, and other philosophers. One common early criticism was that his new views were threatening to the Catholic and Christian faith.[[CiteRef::Jolley (1992)]] In 1663, his works were placed on the Catholic Church's ''Index of Forbidden books'', and in 1671 his conception was officially banned from schools in the Catholic world. In the early modern period, theological propositions and natural philosophical propositions were not seen as belonging to separate domains, but rather formed parts of an integrated [[Scientific Mosaic|scientific mosaic]]. Aristotelian natural philosophy had been carefully adapted to render it consistent with Catholic faith. Descartes' novel natural philosophy introduced many inconsistencies that needed to be [[The Zeroth Law|reconciled]] before his theories could be [[Theory Acceptance|accepted]]. [[CiteRef::Barseghyan (2015)|p. 190-196]][[File:Woman receiving the Eucharist.jpg|right|400px]]One specific theological criticism of Cartesian natural philosophy had to do with the Catholic sacrament of the holy Eucharist, in which bread and wine are said to be transformed into the body and blood of Christ. The dogma of the ''Real Presence'' maintained that in this sacrament, Christ is really (as opposed to metaphorically or symbolically) present in the bread and wine. Centuries earlier, the Catholic saint, Thomas Aquinas(1225-1274)had posited an Aristotelian explanation for the ''Real Presence'' which had become the accepted Catholic ''doctrine of transubstantiation''. The doctrine held that in the Eucharist, the Aristotelian substance of the bread and wine were replaced by the body and blood of Christ, while their forms (that of bread and wine) remaining unchanged. In Descartes' corpuscularism, bread and wine differed from flesh and blood because they had a different arrangement of corpuscles. There is no obvious way that one could appear as the other. The Anglican church, the state church of England following its break with the Catholic papacy in the 1530's did not accept the ''doctrine of transubstantiation''. Thus Cartesianism did not face objections based on it, and became accepted at Cambridge University by 1680. Catholic Paris didn't accept it until 1700. Many solutions reconciling Cartesianism and the ''Real Presence'' had, by then, been proposed. Barseghyan speculates that the one accepted by the Parisian community was that proposed by Antoine Arnauld(1612-1694)in 1671, in which Christ's presence in the Eucharist was due to a miracle beyond human comprehension, and outside the ordinary course of nature described by Cartesianism.[[CiteRef::Barseghyan (2015)|p. 194]]

Descartes' physical natural philosophy did not fare nearly so well. Within fifty years, Issac Newton Another notable objection came from Princess Elizabeth of Bohemia (16421618-17261680) formulated a more mathematically precise and explanatorily powerful physical theory, which became the accepted who questioned Descartes’ theory of substance in a letter dated the physical worldtenth of May, 1643. It rejected In it, she asks “Given that the soul of a human being is only a major tenet of thinking substance, how can it affect the bodily spirits, in order to bring about voluntary actions?”[[CiteRef::Descartes (2009)]] Descartes' corpuscularism by positing would never gives a gravitational force that acted at a distancesatisfactory answer to this central question over the course of the correspondence. NewtonIn 1747, in his ''L'Homme machine''(''Machine Man's laws of motion') Julien Offray de La Mettrie (1709-1751) raised another simple, however, bore important similarities but devastating objection to Descartes' supposition that human reason must be due to those formulated earlier an immaterial mental substance. He noted that reason can become impaired by Descartesmaterial causes such as drunkenness and fever. [[CiteRef::Clarke De La Mettrie (19921996)]] As practicing scientists. In the nineteenth century, Princess Elizabeth's objection became far more poignant with the formulation of the law of the conservation of energy, researchers like Newton and Robert Boyle which implied causal closure of the physical world to influence by a mental substance. In the early twentieth century, the mathematician Alan Turing (16271912-16911954)did notshowed that it was possible to construct a general purpose machine capable of performing any possible mathematical computation, as did thereby demonstrating that a general purpose machine was possible and refuting Descartes' core argument against a mechanical understanding of human reason. By the end of the twentieth century, seek certain knowledge the relevant scientific communities of neuroscience and cognitive science had rejected the real essences idea of material objects. Insteada mental substance and sought a mechanistic physical explanation for the mind [[CiteRef::Bechtel (2008)]], they sought an ordering of phenomenal experience which would enable them though there was still no agreement as to predict nature's course with the best available theorywhether consciousness could be explained in this fashion. [[CiteRef::Osler 1970Chalmers (1996)]]

Descartes ' physical natural philosophy did not fare nearly so well. Within fifty years, Isaac Newton (1642-1726) formulated a more mathematically precise and explanatorily powerful physical theory, which became the accepted theory of the physical world. It rejected a major tenet of Descartes' corpuscularism by positing a gravitational force that acted at a distance. Newton's laws of motion, however, bore important similarities to those formulated earlier by Descartes. [[CiteRef::Clarke (1992)]] As practicing scientists, researchers like Newton and Robert Boyle (1627-1691) did not, as did Descartes, seek certain knowledge of the real essences of material objects. Instead, they sought an ordering of phenomenal experience which would enable them to predict nature's course with the best available theory. [[CiteRef::Osler (1970)]] Descartes' method itself was criticized by two sympathetic figures; Antoine Arnauld and Marin Mersenne. Their criticism had to do with Descartes demonstration of the existence of God, which is the linchpin of his method. Descartes claims claimed that our belief in the reliability of the clear and distinct perceptions of the human intellect depends on our knowledge of the existence of God as the source of that capacity. But how could that knowledge be established in the first place? If we answer that we can prove God's existence from premises we clearly and distinctly perceive, then the argument collapses into circularity. Since Descartes' argument that is it is possible for us to have certain scientific knowledge of the world fails with it, since it depends on God to underwrite the reliability of our senses and intellect. This criticism, called the '''Cartesian Circle''', was never successfully countered. Within a generation, Descartes quest for certainty in scientific knowledge was widely recognized to have failed. [[CiteRef::Cottingham (1992)]][[CiteRef::Ostler (1970)]] In 1650, [[John Locke ]] and the British Empiricists brought forth a new conception of scientific knowledge that was more modest than Descartes' failed quest for certainty. The empiricists argued for experience, rather than a priori reason, as the basis for human knowledge, and sought a philosophy of science more in keeping with scientific practice. [[CiteRef::Uzgalis (2016)]][[CiteRef::Osler (1970)]]

|Page Status=Needs EditingEditor Approved}}{{YouTube Video|VideoID=yFH7i3Lx7IA|VideoDescription=Hakob Barseghyan's lecture on Cartesian Worldview|VideoEmbedSection=Major Contributions