Descartes' Cogito: Understanding 'I Think Therefore I Am'

"I Think Therefore I Am": Descartes' First Principle

"I think, therefore I am." This text reflects Descartes' discovery of the first principle of philosophy. In the first lines, Descartes expresses doubt regarding the testimony of the senses. This is the first level of methodical doubt, invalidating any scientific certainty and the apparent evidence of external reality to thought. From the third line, the text reflects the second and third levels of doubt: the inability to distinguish waking from sleep, and the risk of error even in the simplest truths of geometry or mathematics. This is the application of methodical doubt to reasoning itself. However, as Descartes reaches this level of depth in implementing doubt as a method, a radical enlightenment emerges as the first certainty: "I think, therefore I am," the first principle of philosophy he sought. This truth is unique and singular in its self-evidence, encompassing both a thought and the subject who thinks. Descartes shows that this first truth is not the result of deduction, but rather an intuition in which the reality of existence itself is given. On this absolute and primary evidence, Descartes built his entire metaphysical system.

The Long Chains of Reasons: Cartesian Deduction

The main idea of this section is that geometric deductions are the Cartesian model of knowledge. Deduction is the mode of knowledge by which reason discovers the connections between simple ideas. In mathematics, it means deriving certain truths from others, and Descartes maintains the same meaning. Deduction is a succession in which intuition is passed to other ideas. The deduction used in mathematics provides us with absolutely certain knowledge, in which reason makes us behave actively. Descartes focused on physical problems, studying them using an approach inspired by the methods of mathematics. In this context, he discovered the need for a method that would address traditional Aristotelian data collection and generalization. Investigating the conduct of mathematics led him to the ground as a basis of this science, and method as the foundation of knowledge. Mathematical deduction was the solution, and it could serve all, as reason, he argues, is one and the same for everyone.