Cartesian Philosophy: Truth, Reason, and Method Explained

Truth

Fitness, or correspondence between a statement and the reality to which it refers. Truth does not lie in correspondence with reality, but is a property of ideas that depends on evidence and intuition. An idea is true when it is obvious or when it can be deduced correctly from obvious ideas.

Reason

The power of judging well and distinguishing truth from falsehood is equal in all men. Its correct use depends on the application of a suitable method. It is the only faculty that can conduct man to the knowledge of the truth; neither the imagination nor the senses can, as these are deceptive. Descartes possesses a blind faith in reason, as it always produces knowledge. There are two modes of authentic knowledge via reason: intuition and deduction.

Method

Certain easy rules thanks to which the observer never takes what is false for true, and reaches all true knowledge of which they are capable. It avoids error and discovers new truths. It is formed by four rules:

• Evidence
• Analysis
• Synthesis
• Complete enumeration

It follows a mathematical model, deduced from indubitable ideas.

Senses

Sensory systems through which the body receives energy that provides a stimulus for the nervous system, converting information about the internal or external environment into sensation.

Certainty

A state of mind where one is committed to the conviction that they are before the truth. It is a subjective state of mind or the subject's own feeling. The opposite of certainty is doubt. Descartes proposes the following criterion: everything that is as clear and distinct as "I think, therefore I am" is true. Therefore, the basis is sure evidence.

Evidence

A property of ideas. An idea is evident when it presents itself to the subject as immediately known, making it impossible to doubt its truth. It provides certainty without resorting to testing or demonstration.

Clarity

One of the traits of evidence. It is the property of ideas that are expressed without darkness, with no difficulty in understanding.

Distinction

One of the features of evidence. It is the presence in the mind of the differences between an idea and all others, so that it is separated from any other idea. It is simple and elementary, containing no other ideas.

Doubt

An uncertainty of mind where one cannot decide for the truth or falsity of a statement until there is reasonable evidence in one direction or the other. Its opposite is certainty. One can distinguish between methodical doubt and skeptical doubt. The skeptic follows the Pyrrhonism of Pyrrho of Elis, a radical and universal doubt that ends in the suspension of judgment. Cartesian doubt is a method that is universal and radical, extending to everything.