Descartes' Method: Certainty, Cogito, and the Mechanistic Universe

Descartes' Methodical Doubt and the Cogito

From a young age, René Descartes held a profound interest in learning, yet he felt that the knowledge he was taught failed to address the pressing problems of his era. He sought to establish a philosophy that could explain the entire situation. This search led him to define a straight path—a method, a set of rules that were certain and easy to follow, making it impossible to mistake the false for the true, and which would gradually lead to the knowledge of everything capable of being known. He emphasized that having good sense is not enough; 'in fact, having a good mind is not the main thing, the main thing is to apply it well.'

The foundation of this method had to be reason. Descartes began by doubting everything: knowledge gained through sensory experience, judgments based on external authority, and even the fundamental principles of mathematics. This process, known as hyperbolic doubt, led him to question the very evidence submitted by his own mind.

In this state of radical skepticism, Descartes arrived at his first certainty, the foundation upon which all subsequent knowledge would be built. Through a single intuition, Descartes realized that he exists because he thinks. He discovered the Cogito, the thinking substance.

This realization is encapsulated in the famous phrase, "Cogito, ergo sum" ("I think, therefore I am"). This serves as the model for all evidence and truth. The Cogito is perceived clearly and distinctly. Descartes concluded that whatever is perceived clearly and distinctly must necessarily be true. This principle became his ultimate test of certainty.

The Existence of God and the World

From the certainty of the Cogito, Descartes proceeds to derive the existence of the infinite substance, God, using three primary arguments. These arguments establish God as the guarantor of external reality:

• The Ontological Argument

  The idea of the infinite being (God) is the idea of a being that lacks no perfection. Since existence is a perfection, the infinite being must necessarily exist. God is thus established as the Infinite Substance.

• The Argument from Self-Limitation

  The 'I' (the thinking substance established by the Cogito) is limited and imperfect. This limited self is incapable of producing the idea of an infinite and perfect substance on its own. Therefore, this idea must have been implanted in the mind by an infinite God.

• The Argument from Causality (Perfection)

  Similar to arguments proposed by St. Thomas Aquinas, Descartes argues that the cause of the idea of God must possess as much perfection as the idea itself represents. Since the idea represents infinite perfection, its cause must be infinitely perfect. Therefore, that perfect cause—God—must exist.

Extended Substance: The Mechanistic World

Following the establishment of the thinking substance (mind) and the infinite substance (God), Descartes derives the extended substance—the world (matter). The movements of this substance are reduced to pure mathematical mechanism. Bodies are defined solely by their measurable extension: length, width, and depth.

Descartes asserts that the entire universe—including animals, plants, and even the physical aspects of human beings—are pure mechanisms. All physical phenomena are explained solely by the movement of particles. This mechanism is purely mathematical, rejecting concepts like "hidden forces" (as proposed by the magical-animistic paradigm) or "final causes" (as used in the Aristotelian paradigm). Descartes thus inaugurated a new era, establishing the mechanistic paradigm in modern science.