René Descartes was the first philosopher who focused on acquiring knowledge about knowledge, giving rise to the new era of epistemology in philosophy, becoming the pioneer of rationalism. According to rationalists, knowledge relies primarily on reason and not on sense evidence. The coherence theory of truth states that knowledge is based on primary or innate ideas, further developed into more complex ideas by mathematical or logical methods. In pursuing the truth about the universe, Descartes invented the methodic doubt, which implies doubting everything except things that one’s mind conceives clearly and distinctively (Soccio, p. 256).
The concept of doubt eventually leads to questioning the very fact of the existence of the thinker. The answer to this is a famous “Cogito, ergo sum”, meaning “I think; therefore I am”. Descartes interprets this as a priority of mental existence over bodily existence (Soccio, p. 261). The very special for Descartes was the idea of the existence of God, and he proved it in the ontological argument, which posits that God is “that than which nothing greater can be conceived”, and the real thing is always greater than an imaginary one. An important concept established by Descartes was Cartesian dualism, which refers to the coexistence of two substances – the corporeal body and an incorporeal mind in the human body.
Reference
Soccio, D. J. (2015). Archetypes of wisdom: An introduction to philosophy. Cengage Learning.