Cartesian Philosophy: Reason, Doubt, and Certainty
Descartes’ Cogito and the Criterion of Truth
The objective was to develop a philosophy by using only genuine reason. A system of interconnected truths, arranged so that the mind grasps fundamental truths as self-evident truisms, with others implied by the proposed premises. Descartes started from scratch and accepted only what his reason offered as indubitable.
To build this philosophy, Descartes believed a method was necessary. The method is not required because human reason is unable to find truth, but rather because human reason, left to itself, is infallible when applied to materials that exceed its level of understanding. This method, which Descartes considered indispensable, must be unique because there is only one science: human wisdom. Descartes’ theory that there is only one science and one method opposes the scholastic Aristotelian tradition, which established distinct sciences and methods.
Reason always operates in the same way, to apply it as needed. There are two modes of production: intuition and deduction.
- Intuition is a purely intellectual activity that is so clear and distinct that it leaves no room for doubt.
- Deduction presupposes intuition; it is necessary to grasp every proposition of deductive reasoning and the connection between them.
The speech is divided into four parts:
- The Rule of Evidence: The criterion of truth. Clarity is the presence of a perception to the mind; distinction is its separation from others. The mind grasps true principles by intuition.
- The Rule of Analysis: This rule refers to the process by which the human mind must arrive at simple natures. Analysis involves dividing complex parts into simpler ones through intuition.
- The Rule of Synthesis: Ordering thoughts orderly from the simplest to the most complex.
- The Rule of Enumeration and Revision: Ensuring completeness and accuracy.
The first application of this method led Descartes to the discovery of analytic geometry. Descartes also used another method known as methodical doubt. This doubt involves doubting everything that can be doubted and provisionally treating as false anything that is in doubt. Doubt is required by the first rule of method: no doubt.
Characteristics of Methodical Doubt
- Universal: It applies to everything that can be doubted.
- Methodical: It is not real doubt, but a method to find certainty.
- Provisional: A proposition doubted at a moment of philosophical inquiry can later be considered true.
- Theoretical: It does not extend to conduct, as we are often obliged to follow unlikely opinions.
Once the process of doubt has fulfilled its primary function, it remains to fulfill its second purpose: to lead to the first certainty, the first truth: “I think, therefore I am” (cogito, ergo sum).
As much as I doubt, I must exist; otherwise, I could not doubt. This proposition is not affected even by an evil genius. As much as I extend doubt, I cannot extend it to my own existence. If I am mistaken, I must exist to be mistaken; if I am dreaming, I must exist to dream, and so on.
For knowledge to be perceived clearly, it requires clarity, distinction, and simultaneity. The cogito possesses these three qualities. Therefore, according to Descartes, for an act to be thinking, it needs to fall on the immediate condendo. There are two types of acts: cognitive acts and acts of will.
The cogito ergo sum is the indubitable truth upon which Descartes proposes to base his philosophy. Descartes defines himself not as a body, but as a thinking being, and considers the criterion of truth to be perceived clearly and distinctly.