Descartes’ Philosophy: Substance, Doubt, and Existence
Descartes’ Philosophy: Doubt and the Foundations of Knowledge
After applying metaphysical doubt, as required by his method, Descartes concludes that there is one thing he cannot doubt: that he is doubting. This is the first certainty, evidence of thinking, not based on extra-rational or empirical data. From this, he deduces the rest of reality (God and the world) through logical processes. This leads to the concept of substance as a distinction between what he knows with certainty (his existence as a thinking subject, the res cogitans) and what he cannot be sure of at the moment (the res extensa and res divina).
Descartes’ philosophy rests on the principle that there is a single, fundamental truth, based on the existence of a unique reason. He believes that everything can be known. In fact, in his “Discourse on Method,” he states that “at the end there will be nothing so obscure that we cannot shed some light on it.” Therefore, Descartes asks how we can achieve true knowledge and concludes that we can only be sure of our knowledge if we apply reason, as it is the only thing we cannot doubt, while the senses can lead to error. Based on these principles, Descartes attempts to develop a simple and rational method to exclude false or unnecessary trials, based on two qualities of reason: intuition and deduction. The goal is to find a first certainty, free from any doubt, employing only reason and without recourse to empirical data. After doubting everything, even what seems obvious (methodological doubt), he realizes that the one thing impossible to doubt is his existence as a thinking subject.
Then, he attempts to demonstrate rationally the existence of God and the material world. He is aware that he only has ideas, which are the objects of his thoughts, realities that cannot be doubted, even if the objects they refer to do not exist. He distinguishes three kinds of ideas: adventitious, fictitious, and innate. Only the latter, absolutely independent of experience, serve as the basis for his purpose. From the innate idea of infinity, and following an argument similar to that of Saint Anselm, he believes he has established the existence of God, which leads to the existence of the material world. This discovery leads Descartes to deepen the idea of substance as that which does not need anything else to exist, thus distinguishing between thinking substance, extended substance, and divine substance.
Key Concepts in Descartes’ Philosophy
1. Explain the meaning of the following concepts in the text of Descartes:
Substance
Descartes defines substance as that which does not need anything else to exist. However, of the three classes of substances he distinguishes (thinking, extended, and divine), only the latter truly meets the conditions necessary to be considered as such. Nevertheless, Descartes maintains the concept to refer to the res cogitans as a way to demonstrate its independence from the material reality or res extensa.
Body
This term refers to Descartes’ extended substance, the material world that we perceive through the senses and whose existence he seeks to demonstrate rationally through the ideas that correspond to the thinking substance. Descartes thus establishes an anthropological dualism, in which the material (body) and spiritual (soul) are independent.