Descartes’ Method and the Limits of Knowledge

Posted on Oct 21, 2024 in Philosophy and ethics

Descartes’ Quest for Certain Knowledge

The Starting Point: Doubting Everything

Descartes begins his philosophical journey with the fundamental question: What can I know with absolute certainty? He acknowledges his existence (“I think, therefore I am”) but questions the nature of this existence and the reliability of his senses. He explores two main aspects:

  1. The Body: Descartes recognizes the possibility of an “evil genius” deceiving him about the information he receives through his senses. This leads him to doubt the existence of the physical world.
  2. The Soul: While bodily functions can be doubted, the act of thinking remains undeniable. This leads Descartes to his second truth: “I am a thinking thing.” He identifies this thinking substance with the soul, distinct and separate from the body.

The Path to New Certainties

Having established his existence as a thinking thing, Descartes seeks to establish further certainties. He revisits his initial doubts:

  1. The nature of reality.
  2. The existence of a material world.
  3. The validity of mathematics.
  4. The existence and veracity of God.

Descartes recognizes that the hypothesis of an evil genius undermines any possibility of certainty. To overcome this, he aims to prove the existence of a truthful God.

The Kinds of Ideas

Descartes categorizes ideas based on their origin, reality, and reliability:

  1. Adventitious Ideas: These ideas seem to come from the external world through the senses. Their reality and reliability are questionable due to the potential for sensory deception.
  2. Factitious Ideas: These are ideas invented or created by the mind, such as mythical creatures. They lack reality and reliability as they are products of imagination.
  3. Innate Ideas: These ideas seem to be inherent to the mind, present from birth. They possess the highest degree of reality and reliability, imposing themselves upon thought with immediate evidence.

Demonstrations of God’s Existence

Descartes offers three proofs for God’s existence, all based on the innate idea of a supremely perfect and infinite being:

  1. Gnoseological Argument: The idea of an infinite being cannot originate from a finite and imperfect being like Descartes himself. Therefore, its cause must be an infinite and perfect being, which is God.
  2. Ontological Argument: The very concept of a supremely perfect being implies existence. Just as a triangle must have three sides, a perfect being must exist. Otherwise, it would lack a crucial aspect of perfection.

Refuting the Evil Genius Hypothesis

With God’s existence established, Descartes dismisses the evil genius hypothesis. A perfect God cannot be a deceiver. Therefore, when something appears to the mind as clear and distinct, it must be true. This restores the validity of mathematics and establishes God as the guarantor of rational evidence.

The Limits of Human Knowledge

Descartes distinguishes between primary and secondary qualities:

  1. Primary Qualities: These are quantifiable and knowable through reason, such as size, shape, number, location, duration, and movement. They are objective and belong to both God and the things themselves.
  2. Secondary Qualities: These are qualitative and known through the senses, such as colors, smells, sounds, and tastes. They are subjective and depend on the perceiver.

Descartes emphasizes that we know ideas, not things in themselves. Our knowledge is a mental representation of reality, and we cannot be certain whether this representation is entirely accurate.

The Modern Rationalist Approach to Knowledge

Modern rationalism, as exemplified by Descartes, is characterized by:

  1. Distrust of the Senses: True knowledge can be attained through reason alone, without relying on sensory information.
  2. Innatism: Certain ideas are innate to the human mind and form the basis of rationality.
  3. Mathematics as a Model: Mathematics serves as the ideal model for rigorous and certain knowledge.

The Importance of Method

Descartes stresses the importance of a proper method for acquiring knowledge. A good method ensures consistent and reliable progress, while a flawed method can lead to error. He believes that humans have similar cognitive abilities, but differ in how they apply them. A sound method allows for the effective application of reason.