section_path: Western/Early modern/Rationalism
section_name: Rationalism
paragraph_text: Rationalism
  
  Another dominant school of thought in this period was rationalism. René Descartes (1596–1650) played a pivotal role in its development. He sought to establish absolutely certain knowledge and employed methodological doubt, questioning all his beliefs to find an indubitable foundation for knowledge. He discovered this foundation in the statement " I think, therefore I am." Descartes used various rationalist principles, particularly the focus on deductive reasoning, to build a comprehensive philosophical system upon this foundation. His philosophy is rooted in substance dualism, positing that the mind and body are distinct, independent entities that coexist.
  
  The rationalist philosophy of Baruch Spinoza (1632–1677) placed even greater emphasis on deductive reasoning. He developed and employed the so-called geometrical method to construct his philosophical system. This method begins with a small set of self-evident axioms and proceeds to derive a comprehensive philosophical system through deductive reasoning. Unlike Descartes, Spinoza arrived at a metaphysical monism, asserting that there is only one substance in the universe. Another influential rationalist was Gottfried Wilhelm Leibniz (1646–1716). His principle of sufficient reason posits that everything has a reason or explanation. Leibniz used this principle to develop his metaphysical system known as monadology.