Descartes’ Methodical Doubt and Cogito Ergo Sum
Descartes: Methodical Doubt and Cogito Ergo Sum. The structure of the Cartesian metaphysical system (the root of the tree of science) corresponds to the division of reality into three substances:
- The self, or substance pensante
- God, or the perfect and infinite substance
- The world, or the substance extensa
Descartes built this system from the application of methodical doubt and found the “Cogito ergo sum.” Let’s see how he did it:
Descartes was convinced that a sure method existed and practiced it to achieve it. This philosopher underwent a universal skeptical questioning (questioning all knowledge). Unlike skeptics, for whom doubt is the final state of mind, for Descartes, it’s the first step in a method leading to the opposite state. Therefore, Cartesian doubt is not skeptical doubt but a method to find the first glimmer of truth: I think.
Methodical doubt uses doubt as a method, a process of philosophical inquiry. It’s deliberately doubting, declaring false anything imaginable that has the slightest reason for doubt. The goal is to find certain truth, free from suspicion. Methodical doubt applies the first rule of method, evidence—finding intuitive truth, presented clearly and distinctly to the human spirit, leaving no reason to doubt it.
Applying methodical doubt, Descartes proceeded layer by layer. The questioning extends to:
- All sensory knowledge: doubting it based on the senses’ fallibility.
- Arguments and deduction: logical errors invalidate science if reasoning is doubted.
- The reality of what we know or perceive: experienced reality might be a dream. The concern is the indistinguishability of dreams from reality.
Descartes described the “evil genius hypothesis” in his Metaphysical Meditations. It posits an all-powerful evil creator, making our minds prone to error, even in what seems obvious. Hyperbolic doubt demands more proof of a good God to ensure clear and distinct ideas correspond with reality.
The first truth of the Cartesian system is: “Cogito, ergo sum” (I think, therefore I am).
This truth is given in intuition: in doubting, the self becomes aware of its existence. The more one doubts everything else, the more certain one is that at least this thought exists.
The “I think” stands even with the evil genius hypothesis because for me to be fooled, I must exist.
With “Cogito, ergo sum,” Descartes found a secure truth to refute skeptics. The method eliminates doubt by considering false anything with the slightest reason for doubt. The existence of self is evident as it thinks.
Descartes then explains truths included in the first:
- The essence of the self: Descartes discovers the self as a substance whose essence is thinking. Through the hypothesis of mental fiction, he concludes that man’s essence is his soul, not his body.
- The criterion of truth: from the Cogito, Descartes gives content to the first rule of method. What is perceived clearly and distinctly, like the “I think,” is true.
- The existence of God: from mental contents, specifically the idea of infinity and perfection, Descartes demonstrates a priori that God exists, guaranteeing certainty. An almighty and loving God cannot deceive in reasoning, eliminating the evil genius hypothesis.
- Existence of the outside world: if only what is clear and distinct is true, and the idea of ‘extension’ is presented inadvertently, considering God’s existence and non-deception, then the idea of a world outside the mind is true.
Thus, the Cartesian system of reality is built, where humans occupy a special place as amphibians living in two parallel, separate worlds: res cogitans and res extensa.