Descartes’ Philosophical Method and Doubt
Descartes’ Method of Reason
There are two ways of knowing: intuition and deduction. Intuition, as defined by Descartes, is not the fluctuating testimony of the senses, but the conception of a pure and attentive mind, arising from the light of reason, leading to simple, absolutely true knowledge. Deduction is defined as any necessary inference from other facts known with certainty. Intelligence discovers connections through inference. The inspiration for this method is clearly Cartesian mathematics.
Descartes states that reason is unique to humans, and therefore there should be a single method for gaining wisdom. He defends the idea of a unified science of reason and the unity of method, inspired by mathematics.
The Four Rules of Method
Descartes proposed four rules for the proper use of reason:
Rule 1: Evidence
Accept nothing as true which is not clearly and distinctly known. Avoid precipitation (accepting confused or obscure ideas as obvious) and prevention (the opposite mistake). The criterion of truth is clarity and distinction, characteristic of simple ideas obtained through intuition.
Rule 2: Analysis
Divide problems into as many parts as possible and necessary for better resolution. Reduce complex problems to simple ideas clearly and distinctly apprehended by intuition.
Rule 3: Synthesis
Proceed in an orderly way from the simplest and easiest to know to the more complex, using deduction to build knowledge with the same clarity and distinction.
Rule 4: Enumeration and Review
Make complete lists and general reviews to ensure nothing is omitted. Analysis and synthesis correspond to the two ways of knowing: intuition (providing clear and distinct ideas) and deduction (extending evidence to the unknown). This method is suitable for reason and its natural way of knowing.
Methodical Doubt
The object of methodical doubt is to find certain truths. This requires a long process of reviewing and rejecting all knowledge previously considered true. The first step is to doubt everything one believes and reject anything initially subject to doubt. This is methodical doubt, the result of applying the first rule: never admit as true what is not known with evidence.
The Cogito: First Truth
The “Cogito, ergo sum” (I think, therefore I am) is the first criterion of truth and certainty, an absolute certainty. Descartes could accept it without scruple as the first principle of the philosophy he sought. The “Cogito, ergo sum” is a truth known by immediate intuition. It is the first truth because it is the result of intuition and possesses the two essential features of obvious truth: clarity and distinction.
The Cogito is more than just the first truth; it is also the model for all truth. With the Cogito, Descartes finds the first truth and also the general criterion of certainty: whatever is perceived very clearly and distinctly is true. This criterion derived from the Cogito requires further substantiation.