Descartes’ Ontology: Reason, Doubt, and Existence
Descartes’ Ontology: A Philosophical Exploration
René Descartes, a 17th-century philosopher, emerged after the scholastic period marked by humanism (focusing on anthropological studies), the Scientific Revolution (with its new theories and discoveries), and the challenges of the scientific method. He is considered the founder of philosophical Rationalism, a school of thought continued by figures like Malebranche, Spinoza, and Leibniz. Rationalism emphasizes human reason, employing the deductive method and affirming the existence of innate ideas. This philosophical stance opposes British empiricism, which is based on experience.
Descartes received an excellent education from a young age and dedicated his life to study. Eschewing reliance on previous philosophers, he sought to innovate and break new ground. He quickly gained fame, leading him to frequently change his residence, fearing potential harm.
Descartes initiated his philosophical project by clarifying his objective: to establish a system of self-evident truths (certainty) through the methodical application of reason. He summarized his method into four fundamental rules: evidence, analysis, synthesis, and enumeration and order. Beginning with evidence, he defined methodological doubt, which operates on three levels: doubting the senses, doubting reason itself, and positing the existence of an evil genius.
This process leads to the conclusion that thought exists, as the very act of understanding all this implies a thinking intelligence. This realization is termed the First Certainty. From this foundation, Descartes identifies three levels of reality: the subject, the subject’s ideas (understanding ideas as mental contents, not Platonic eidos), and external reality. However, this leads to solipsism: only the existence of one’s own thought is known. To overcome this, Descartes relies on innate ideas of infinity and perfection. He argues that the presence of these ideas, given our own finite and imperfect nature, implies that they originate from God. The existence of God allows us to dismiss the evil genius hypothesis and regain confidence in reason.
Descartes asserts that ideas, God, and a world external to our consciousness exist, but they must be ordered, which is achieved through the concept of substances.
Descartes employs the notion of substance by emphasizing its independence, in contrast to accidents, which are dependent on substances. In other words, substances are entities that do not require anything else to exist. However, if this definition is applied strictly, it applies only to God, leading to a monistic view of substance. Descartes then proposes two uses of the word “substance”:
- Infinite substance: God
- Finite substances: these only need God to exist. We can distinguish two types of finite substances:
- Res cogitans: Thought
- Res extensa: Matter/Extension
There is no similarity between res cogitans and res extensa, and their properties are opposite (e.g., immaterial vs. material).
To define material objects, Descartes distinguishes between primary qualities and secondary qualities, ultimately grounding them in extension. He illustrates this with a clear example:
Consider a piece of wax. Initially, it has a certain color, weight, and volume. However, imagine that a heat source is applied, causing the wax to change, acquiring a different color, weight, and volume. Despite these changes, we recognize that it is still the same piece of wax.
Thus, Descartes prioritizes the primary quality of extension, the property of occupying space. He concludes that everything in the universe consists of God, thought, extension, and accidents.