Descartes’ Methodical Doubt and the Existence of God
Descartes’ Method of Doubt and Knowledge
1. Knowledge: For Descartes, knowledge consists of discarding doubt through clear and distinct intuition of a proposition or opinion. Evidence relates only to reason; that is, the immediate understanding that a proposition is true. Because the senses can deceive us, we cannot rely on them. Knowledge is reached through deduction from these clear and distinct propositions, following the rules of the method step by step. The method guarantees the certainty of deductive knowledge. Therefore, knowledge is both intuitive and deductive.
2. Doubt: Doubt is the initial step in applying the method to attain knowledge. It extends to all views acquired without critical thinking, avoiding the incorporation of misjudgments into knowledge. However, Cartesian methodical doubt is not the doubt of skeptics, who deny the existence of truth. Instead, it is the starting point to reach that truth, excluding all doubt.
Commentary on Descartes’ *Discourse on Method* (Part IV)
The text is a fragment from Descartes’ *Discourse on Method*, Part IV. Descartes attempts to demonstrate the existence of a perfect being. He argues that the idea of perfection cannot come from himself, as he is imperfect (due to his doubting). Therefore, the idea of perfection must originate from a perfect being outside of him, which is God. This perfect being implanted in him the idea of perfection.
Starting with doubt, Descartes seeks a truth that cannot be doubted, from which all other knowledge can be derived. To find this truth, he must doubt everything. He doubts the senses (as they sometimes deceive) and even the external world, as it is sometimes impossible to distinguish reality from dreams. He even introduces the possibility of an evil genius that constantly deceives us. At this point, everything is doubted, and nothing seems certain.
However, despite this radical doubt, Descartes finds an absolute truth: the existence of the subject who thinks and doubts. “I think, therefore I am” (Cogito, ergo sum). Even if he doubts everything, the very act of doubting confirms his existence.
According to Descartes, thinking rests on ideas, not things. He thinks not about the world directly, but about the *idea* of the world. To ensure that the idea of the world corresponds to the world as reality, Descartes analyzes ideas rigorously to determine if any can break the circle of thought and lead to extra-mental reality.
He distinguishes three types of ideas:
- Adventitious ideas: Seem to come from external experience.
- Factitious ideas: Constructed by the mind from other ideas.
Neither of these can serve as a starting point for demonstrating the existence of extra-mental reality.
However, there are innate ideas, which cannot come from external experience or be constructed from other ideas. They are inherent in thought itself.
Among innate ideas, Descartes discovers the idea of infinity, which he identifies with God. Since God exists and is perfect, He is good and truthful and cannot allow Descartes to be deceived into believing that the world exists when it does not.
Therefore, while the senses can deceive, the outside world is real. God guarantees that Descartes’ clear and distinct ideas correspond to extra-mental reality.
Substance and Dualism
This relates to the concept of *substance*, something that exists and needs nothing else (except God) to exist. Strictly speaking, this applies only to God, but it extends to the soul and body, which are finite substances.
In conclusion, the distinction between thinking substance (the soul) and extended substance (the body) embodies the dualism in modern philosophy. This dualism creates one of the main problems of rationalism: the communication between the two substances.