Descartes’ Philosophy: Existence of Self, God, and the World
Principles of Descartes’ Philosophy
To solve this problem, Descartes analyzes the nature of ideas, elements that conform to our thinking. In this analysis, he is trying to reach an external reality. He realizes that all ideas are equal and identifies three types:
- Adventitious ideas: Those coming from outside of our external experience (e.g., the idea of a home).
- Factitious ideas: Those invented or feigned by the mind, built upon other ideas (e.g., the idea of a siren).
- Innate ideas: Those ideas that thought itself possesses (e.g., the idea of existence), which are not built through the mind nor through experience.
Among these ideas, Descartes discovers the idea of infinity to be essential, immediately identifying it with the idea of God. The French philosopher asserts that this is neither an idea based on experience (adventitious) nor an idea constructed by the mind (factitious). Therefore, the idea of God is an innate idea. This opens the deductive process that allows us to demonstrate the existence of the external world and the validity of sensitive knowledge, starting from the idea of God. But first, he must demonstrate God’s existence, for which Descartes uses three arguments. The first two are based on the principle of causality.
The first argument, “God is the cause of my idea of perfection,” is based on the principle that there must be at least as much reality in the cause as in the effect. From this, Descartes concludes that God is the cause of our idea of perfection and infinity. The second argument is a variant of the previous one: “God is the cause of my being and my perfection.” It states that neither conservation nor creation can come from oneself. Therefore, there must be a superior being who has placed the innate idea of God within us, and this being is God. Finally, the third argument, known as the ontological argument, proves the existence of God based on the definition of God as a perfect being. Descartes concludes that God exists not only in thought but also in reality. Thus, he concludes that it is impossible to think that God, who is the sum of all perfections, does not exist, as existence is a perfection.
In this way, Descartes establishes that God is the guarantee of the criterion of truth, a guarantee of our ideas, which are presented clearly and distinctly. This is how Descartes concludes that the hypothesis of the evil genius is impossible. But then the question arises of why we make mistakes. To explain this, Descartes distinguishes between intellect and will. Errors are caused by the will, specifically by a misuse of freedom. Therefore, according to Descartes, because God exists, the external world exists (because of God, we have the inclination to believe that ideas are based on corporeal things), but perhaps not as we perceive it.
Descartes states that matter is composed of qualities, divided into two categories: primary and secondary. Primary qualities are objective and real, those that can be measured, while secondary qualities cannot be measured and depend on the subject’s appreciation. Therefore, regarding bodies, we can only consider the quantifiable, which Descartes identifies as extension and motion. He posits that matter is built of blocks of different sizes, joined together compactly without a vacuum, and that all living things are a sort of complex machinery. This is why Descartes’ physics is considered mechanistic.
Descartes’ Three Substances
From the first truth, Descartes inferred the existence of the self, God, and the bodies that make up the three generic elements, called substances. He distinguishes three types of substance, understood as “that which exists in such a way that it does not need anything else to exist”:
- The self (res cogitans): Also called the soul, it is indivisible and therefore immortal.
- Corporeal substance (res extensa): Also called the world, it is characterized by being measurable (studied by physics).
- God (res infinita): Considered as having the attributes of infinite wisdom, infinite power, etc.
Thus, these three objects are the foundations of metaphysics. However, it is necessary to explain why Descartes makes this great separation between two substances, soul and body (anthropological dualism). The soul belongs to the realm of freedom, while the body belongs to the realm of science. They are separated to safeguard individual freedom while supporting the mechanistic approach, as freedom must be separate. Descartes needed to find a point of communication between them and eventually found it in a specific gland in the brain called the pineal gland, although this did not fully solve the problem of communication between soul and body.
Conclusion
Once developed, Descartes’ philosophy must be based on certain criteria and regain the external world. To do this, he first removes doubts by analyzing ideas and concluding that there are three types: adventitious, factitious, and innate. Among the latter, he identifies the idea of infinity with God, concluding that God is an innate idea. To support this, he uses three arguments: the infinite cause, existence, and the ontological argument. With the existence of God, he also guarantees the existence of an external world. He identifies three substances from the first truth: soul, world, and God. Thus, Descartes ultimately bases his philosophy on the three pillars of metaphysics.