Descartes, Rene

(1596-1650) philosopher and mathematician; "I think therefore I am" goal of knowledge is certainty; certainty derives from intuition and deduction; certainty requires systematic doubt (methodological skepticism ); this systematic doubt leads to indubitably clear and necessary first principles from which all necessary and genuine knowledge can be deduced (e.g., the science of geometry). The Cartesian method invokes 4 rules as guides in moving from opinion to science: Never accept anything as true unless it is clearly and inescapably so; Analyze or reduce a problem to resovable parts; Organize particulars into general knowledge; Check for completeness and negative cases. Reality for man is 2 substances: matter (i.e., extension in space and time); and mind (unextended thinking spirit mirroring the material world). God is absolute substance, uncreated, unmoved, and perfect creator of matter and human minds. As the inner world of consciousness, mind is free and motivated by God. As the outer world of space, matter constitutes the mechanism of the world machine set in motion by God, who is first cause, and is continued in motion according to inherent and necessary laws of nature (determinism ).