Rene Descartes was one of the modern world?s great intellects. He was principally a philosopher, mathematician and scientist, but he also pursued a wide variety of other interests including metallurgy and fencing (on which he wrote treatises?now lost). Working with the comprehensive and acute energy of the third ray soul his philosophical approach advocated a method of ?systematic doubt? intended to lead to certainty in all areas of thought which the human mind might explore. He is best known in philosophical circles for his dictum, ?Cogito ergo sum? (?I think, therefore I am?) and for proposing a metaphysics which strictly divided mind from matter. As a mathematician he is credited with inventing analytic geometry (presented in his book Geometry) as well as number of important conventions in mathematical notation which are still in use today. He also studied a number of scientific subjects. In his Dioptrics, he presented the law of refraction, and in his Meteorology he explained the rainbow. He was also a moral philosopher and (although nominally a Catholic), was an outspoken (if wary) advocate of religious tolerance. Descartes surely believed in God, but found his calling in the glorification of reason. The conclusions he reached when thinking about God, the universe and man (and especially his advocacy of Copernicus? astronomical theories) placed him on a collision course with Church dogma, for which reason he was ever-vigilant about his safety. refer to:http://www.esotericastrologer.org/EA%20Essays/EAessaysMDR29.htm