Descartes’ Rationalism: Reason, Method, and Metaphysics

Posted on Jan 30, 2025 in Philosophy and ethics

Descartes and Rationalism

1. Reason

Key elements of rationalism:

  • The importance of reason in understanding the origin of knowledge, compared to sense or experience.
  • The existence of innate ideas or truths, which are activated during the occurrence of an experience.
  • Reason is the opposite of the criterion of authority, i.e., the imposition of tradition or belief by a person of great prestige.
  • The model is a universal mathematical science.
  • Reason is the only instrument to know reality.

2. The Method

Descartes thought the only reliable way to access knowledge was through reason. However, reason was not enough unless it was implemented well and followed a safe path. Therefore, it is necessary to use reason to reach the truth correctly. To do things through reason, you need a methodological path. The method is described in his Discourse on the Method in three phases:

  1. The initial training provided by the Jesuits offered him a serious knowledge of the materials they studied.
  2. Then, he devoted himself to study in the ‘book of the world’, i.e., the reality of the world.
  3. He went to study himself, because truth is found in reason and in one’s own thoughts.

The rules of the method should be simple and easy:

  1. Evidence, clarity, and distinction: Not accepting as true anything that is not evident. To avoid haste and prejudice, only accept what is presented to the intellect clearly and distinctly, leaving no doubt. This is intuition.
  2. Analysis: Divide each of the difficulties into as many parts as possible and necessary to resolve them.
  3. Order and synthesis: Proceed in an orderly manner, ranging from the simple to the complex through deduction.
  4. Enumeration and review: Make complete enumerations and general reviews to be sure of not omitting anything.



3. The Application of the Method

Methodological doubt: He turned the question on the basis of the method, decided to use the question to find certainty. In the first rule of the method, he states to use doubt. To place knowledge on a sure, firm, and final foundation, he had to bracket everything that was indubitable. To doubt something does not prove anything, it means to stay the trial on that which has no security. Therefore, certainty and doubt are part of his method. It is a universal question, which is applied to all knowledge in the search for certainty.

Reasons for doubt:

  • The experiences proceeding from the senses are not always reliable.
  • The difficulty of distinguishing between waking and dreaming.
  • The hypothesis of the ‘evil genius’.

1st certainty: I think, therefore I am: He needed to find a truth that would be impossible to doubt, and found a truism: the very existence of himself as a thinking subject, who doubts. He explains that his question is because of something, and immediately thinking implies existence. This firm principle is beyond doubt and is the first principle of his philosophy. This first certainty is immediately evident to the intuition through which it is accessed.

4. Metaphysical Conception of Reality

Starting from the concept of himself as a thinking being, he derived his first truth, which was the couple of concepts: thinking and existence. Referring to traditional metaphysics and Being, thoughts take the form of ideas, which are the content of thought. To explain the contents of the configuration of reality, he considered three substances:

  • Man or thinking substance. The self is a thinking substance.
  • God or infinite substance, whose existence follows from the very idea of God.
  • The world or extensive substance, which is guaranteed by God.