Principles of Cartesian Rationalism and Methodical Doubt

The Four Rules of the Cartesian Method

René Descartes applied four fundamental rules to his method, which are designed to ensure clarity and truth. These rules include:

• The Rule of Evidence: To avoid precipitation and prejudice by only accepting what is clearly and distinctly true.
• The Rule of Analysis: Whereby a problem is broken down into its simplest parts to be better understood.
• The Rule of Synthesis: Which proceeds from the simplest objects to the most complex knowledge.
• The Rule of Review: To perform comprehensive revisions and ensure that no step in the procedure has been omitted.

Methodical Doubt and the Search for Truth

Descartes utilizes methodical doubt as a tool to reach an ultimate goal: obtaining a clear understanding through reason. In the pursuit of clear ideas, the senses must be doubted, as the sensations we receive are not always reliable and can be a product of deceit. Consequently, sensory perception is discarded as fallible.

The Dream and Evil Genius Hypotheses

Through the dream hypothesis, Descartes suggests we can doubt the existence of our own bodies, as our physical reality could be nothing more than a dream. Furthermore, he posits the evil genius hypothesis, which raises doubt even about the veracity of mathematical truths and the contents of our consciousness.

The Cogito and the Discovery of the Self

Descartes concludes that if he is being deceived, he must exist to be the subject of that deception. This leads to his first certainty: "I think, therefore I am" (Cogito, ergo sum). By decomposing problems to find the truth, he begins reconstructing the world. The application of the Cartesian method leads to the existence of the self as a thinking thing.

Classification of Ideas and Substances

It is a serious error to confuse the existence of the cogito with the independent existence of the contents of the mind. Descartes reflected on his own thoughts and categorized ideas into three types:

• Adventitious ideas: Those resulting from external experience.
• Factitious ideas: Imaginary constructions created by the mind.
• Innate ideas: Products of the natural functioning of reason.

Innate ideas serve as a reliable starting point for knowledge. While they may not be apparent from birth, they arise over time through the use of reason.

The Three Substances

Descartes identifies three kinds of substances: thinking substance (res cogitans), extended substance (res extensa, referring to external physical features), and eternal substance (God).

The Existence of God and Cartesian Ethics

Moving beyond Scholasticism, Descartes concludes that the idea of perfection within us must come from a perfect being. This perfect being is God; since existence is a perfection, God must necessarily exist. If He were not perfect, He would not be God.

Provisional Cartesian Ethics

Cartesian ethics defines the fundamental activity of man as the search for truth through reason. For practical life, Descartes provides provisional moral precepts: observe the laws and customs of your country, remain firm and resolute in your actions once decided, and strive to change your own desires rather than the order of the world.