Descartes' Method of Doubt and the Cogito

Descartes' Quest for Certainty

The philosophy of René Descartes was part of a grand project to unify all sciences into a single, cohesive system. He aimed to formulate a rigorous method, based on four fundamental rules, to establish provisional moral standards, develop his Metaphysics, and substantiate his Physics. This construction of Metaphysics was essential for discovering fundamental truths.

Unifying Knowledge: Descartes' Philosophical Project

Descartes' thought began with a preliminary search for absolute certainty. He resolved to treat everything as false if there was even the slightest doubt, even temporarily, thereby initiating his methodical doubt.

The Four Rules of Method

• Evidence: Accept nothing as true that is not clearly and distinctly perceived.
• Analysis: Divide each problem into as many parts as possible for better resolution.
• Synthesis: Proceed from the simplest to the most complex, building knowledge step by step.
• Enumeration: Make complete reviews to ensure nothing has been omitted.

The Method of Methodical Doubt

Descartes' methodical doubt consisted of three progressive degrees:

First Degree: Doubting the Senses

He first doubted the senses, as they sometimes deceive us. He considered it probable that they always deceive us, making him hesitant to trust any sensory information.

Second Degree: Doubting Reality and Dreams

Secondly, he doubted the perception of reality itself. Objects sometimes confuse with reality, and dreams cannot be clearly distinguished from wakefulness. He questioned these perceptions in relation to everyday notions and sciences.

Third Degree: The Evil Genius Hypothesis

Thirdly, he extended his doubt to mathematical propositions. Although these appear clear and distinct, he hypothesized the existence of an "evil genius" or powerful deceiver who might mislead him even about these seemingly certain truths. With this, the process of doubt reached its maximum extent.

The Cogito: "I Think, Therefore I Am"

Descartes employed doubt as a tool to find an undeniable truth. He discovered this truth in the statement: "I think, therefore I am" (the cogito). Analyzing this truth immediately revealed two initial consequences: what he is (a subject or thinking thing) and the criterion for certainty and truth.

From Cogito to Res Cogitans

When Descartes asserts his own existence, he does so by assuming that thinking is not merely an activity but requires a substance or a subject to sustain it. Therefore, he rightly asserts that he is a "res cogitans" (a thinking thing), a subject that thinks. Thus, from this truth, he can only deduce that he himself is the primary foundation of his knowledge. His metaphysics is centered on the notion of substance, and thought is regarded as a substance, not merely as a cognitive activity.

The Criterion of Truth and God's Existence

He arrived at the conclusion that "I think, therefore I am" is the only thing that truly ensures its own existence, appearing very clearly and distinctly. Therefore, everything that is presented clearly and distinctly is true. However, despite finding this criterion of certainty, he could not proceed further with its application due to the "evil genius" hypothesis, which suggested he might still be deceived. To be able to apply this criterion universally, he had to demonstrate the existence of God, ensuring that God is not a deceiver who would make him take what is distinctly perceived as real when it is not. Furthermore, the existence of God had to be established from the self, as the ultimate aim was to dispel doubt about the real existence of things distinct from his own thinking.