Descartes’ Philosophy: A Rationalist Approach to Knowledge
1. Descartes’ Ideas
Thinking and Existence
Thinking generates ideas. Descartes sought to demonstrate the existence of the outside world and the relationship between ideas and things.
Types of Ideas
- Learned: Sensitive data from the outside world or taught by others. These do not guarantee a connection to the extramental world.
- Fictitious/Artificial: Invented or created by the mind from other thoughts (e.g., the idea of a mermaid). These do not guarantee a connection to the extramental world.
- Innate: Neither from external objects nor created by us. They are in our minds and arise spontaneously, forming the foundation of our thinking. These do not guarantee a connection because we could be deceived by an evil genius.
Descartes aimed to demonstrate the existence of God as a foundation of knowledge.
2. The Existence of God
Descartes avoided arguments based on experience since the outside world was in doubt.
Arguments for God’s Existence
- The Imperfect Mind: The ‘I’ (or soul/res cogito) is flawed because it doubts. The idea of perfection within us implies a perfect being (God). An imperfect being cannot create the idea of perfection.
- Dependent Beings: Imperfect beings are dependent on a perfect being.
- St. Anselm’s Argument: Perfection implies existence. The very notion of God means God exists. If God exists, God must be perfect.
Descartes’ dualism posits that the mind (res cogito) strives for perfection, while the body (res extensa) is flawed. The combination of the two results in imperfection.
3. Defending God’s Existence
Descartes argued for certain truths derived from reason, criticizing empiricism (ideas from senses).
He questioned the origin of the idea of the soul and God, suggesting innate ideas as the source.
He distinguished between the intelligible (knowable through reason) and the unintelligible (unknowable).
4. God Guarantees Evidence
If God exists and is perfect, God would not deceive us. Thus, our innate ideas, instilled by God, are true. Clear and distinct ideas are true, requiring the non-existence of an evil genius and the existence of a perfect God.
5. The Outside World
Descartes argued that the world exists, and God ensures that our perception of the world is accurate, even if we can make mistakes in applying reason.
6. The Three Substances
Descartes proposed three levels of reality, each with a defining characteristic:
- God: Infinite substance – perfection
- Mind: Thinking substance – thought
- Body: Extended substance – extension
Substance (rationalist): That which needs nothing else to exist.
Substance (Descartes): That which needs nothing else to remain.
7. Cartesian Dualism
Res cogito (soul) and res extensa (body) belong to different natures and are incompatible. Descartes’ mechanistic view of nature (like a machine) includes the human body. Human freedom is ensured by the distinct nature of the mind (open) compared to the mechanical body. The connection between body and soul is through the pineal gland.
8. Descartes and Other Philosophers
Meaning of Soul
- Plato: Discovering truth is remembering what the soul already knows. The body is a prison for the soul. Knowledge belongs only to the soul.
- Descartes: Senses alone do not provide knowledge. We know the outside world through reason. Only the ideas of God and the soul are beyond the senses.
Empirical Knowledge
- Plato: Two worlds: the world of appearances (changeable) and the world of ideas (eternal).
- Descartes: Senses can deceive us. Reason is the primary source of knowledge. Senses provide the material for reason to process.
Theoretical Knowledge
- St. Augustine: Reason and faith are distinct but aim to help humans understand divine truth. An inner journey is required, illuminated by God (metaphor of the sun).
- Descartes: Illumination is not needed for knowledge.
Descartes’ Philosophy
1. Sociocultural Context of the 17th Century
- Absolute Monarchy: Descartes sought a definitive basis for human knowledge, showing that humans can access absolute knowledge.
- Counter-Reformation: Catholicism’s response to Protestantism. Descartes aimed to reconcile faith and reason.
- Triumph of Science: Descartes believed philosophy could achieve truth with the right method.
2. Rationalism
Descartes inaugurated philosophical rationalism, emphasizing reason over the senses. Rationalism and empiricism are contrasting movements.
3. Shortcomings of Previous Philosophy
Descartes criticized the lack of progress and agreement in philosophy, aiming to make philosophy as unquestionable as mathematics.
4. The Need for a Method
Descartes sought a method to discard false beliefs and achieve true knowledge, inspired by the methods of mathematics (intuition and deduction).
6. Unity of Knowledge and Reason
Descartes believed in a unified science with a single valid method for all disciplines.
7. The Four Rules of the Cartesian Method
- Evidence: Accept only clear and distinct truths.
- Analysis: Divide complex propositions into simpler ones.
- Synthesis: Reconstruct complex propositions from simpler ones.
- Enumeration: Review to avoid errors and omissions.
8. Methodical Doubt
Doubt as a means to achieve truth. Descartes distinguished between skeptics (doubt as an end) and rationalists (doubt as a means).
Properties of Doubt
- Universal: Question everything.
- Methodical: Doubt as a means, not an end.
- Provisional: Temporary, to achieve true knowledge.
- Theoretical: Applied only to theory, hence the provisional morality.
9. Provisional Morality
Interim moral laws:
- Obey laws and customs, follow the wisest opinions, choose moderate opinions.
- Be firm and resolute in chosen opinions.
- Conquer oneself rather than fortune, change desires rather than the world.
10. The First Truth
Descartes doubted sensory data, the distinction between dreams and reality, and the possibility of an evil genius.
The first truth: “Cogito Ergo Sum” (I think, therefore I am). This establishes the relationship between thought and existence and forms the basis for clear and distinct ideas.
Clear: Present and manifest to the attentive mind.
Distinct: Precise and different from other objects.