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|Brief=a French natural philosopher; who is today considered one of the most influential figures in modern philosophy

|Summary=Descartes rejected the Aristotelian-medieval mosaic accepted for most of the previous two thousand years, and laid the foundations of a new mechanistic 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)]]

Descartes’ major writings came in a time of social and intellectual upheaval in Europe. Before writing his major works, he was a participant in the Thirty Years War. He travelled extensively around Europe at a time when the continent was embroiled in both reformation and counter-reformation, 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 varied sources, including varieties of Platonism, Hermeticism, and the 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)]]

===Cartesian Natural Philosophy===

Descartes scientific theories about the natural world were grounded in a metaphysical foundation, in turn deduced by the application of his rationalist methodology. He wrote that "the whole of philosophy is like a tree. The roots are metaphysics, the trunk is physics, and the branches emerging from the trunk are all the other sciences, which may be reduced to three principle ones, namely medicine, mechanics, and morals".[[CiteRef::Clarke (1992)|p. 271]] One ought to construct a metaphysics first, based on criteria independent of observation, and subsequently consider physical theories consistent with the metaphysical foundation. His natural philosophy was in stark contrast to the accepted Aristotelianism. In Aristotelian natural philosophy all objects were a compound of form and matter, a concept called hylomorphism. Form gives material bodies their distinctive properties, and makes them different from one another. It explains why fire rises and stones fall. Matter is what all material bodies share in common. All things have teleological goals or purposes. [[CiteRef::Shields (2016)]]

|Related Topics=Method, Methodology,

|Page Status=Editor Approved

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