René Descartes' Philosophy: Core Concepts and Influence

René Descartes' Philosophy: Key Concepts and Comparisons

Comparison with Plato

Both Descartes and Plato defended the idea that knowledge was innate. However, Plato believed innate ideas were known from the Anima before being joined to the body, while Descartes held that ideas are intrinsically linked to true reason.

Both authors also defended the duality of man, composed of soul and body. For Plato, the soul is where truth resides, and it is a perfect, naturally pre-existing, divine entity before joining the body. In contrast, Descartes' concept of the soul is tied to the "Cogito" ("I think") and does not have a separate existence or reality apart from the body in the same way Plato conceived it.

Both philosophers are rationalists, arguing that true knowledge stems from reason, not solely the senses. However, a key difference lies in their views on knowledge acquisition: for Plato, knowledge is recollection (memory), whereas for Descartes, it is reasoning.

Descartes' Rules of Method

• Rule of Evidence

  Never accept anything as true without clear and distinct evidence of its truth.

• Rule of Analysis

  Divide each problem under examination into as many parts as possible, as required for a better solution.

• Rule of Synthesis (Summary)

  Direct thoughts in an orderly manner, starting with the simplest and easiest objects to know, and ascending slowly to the knowledge of the most complex compounds, even assuming no natural order exists among them.

• Rule of Enumeration or Induction

  Make enumerations so complete and reviews so general that one can be certain nothing has been omitted.

Descartes' Methodological Doubt

Descartes employed systematic doubt to arrive at certainty. He questioned:

• The data from the senses, which sometimes deceive us.
• The existence of a world of objects external to us, similar to how dreams can deceive.
• Even truths in mathematics, considering the possibility of a deceiving demon.

The "I Think" (Cogito) as First Criterion of Truth

If the senses deceive us, how can we know if anything exists? Descartes concluded that if he doubted, he must exist as a thinking being. The act of thinking itself proves his existence: "I think, therefore I am" (Cogito, ergo sum). This serves as the first undeniable truth and criterion for certainty.

Descartes' Classification of Ideas

• Adventitious Ideas

  Those that seem to come from outside our experience (e.g., horse, man).

• Factitious Ideas

  Those constructed by combining other ideas (e.g., centaur, chimera).

• Innate Ideas

  Those not derived from experience or dependent on our will, but inherent to our nature (e.g., the idea of infinite existence, God).

Arguments for the Existence of God

• Ontological Argument

  God, being a perfect and infinite being, necessarily encompasses existence as a perfection.

• Argument from Infinity

  The idea of an infinite and unlimited being must have an infinite cause, which is God.

• Causality Argument Applied to Self

  I am finite and imperfect. My existence must have a cause. Since I am imperfect, I cannot be the cause of my own existence or of the idea of perfection within me. Therefore, a perfect being (God) must have created me, as only perfection can create perfection.

Descartes' Classes of Substances

• God (Infinite Substance)

  The uncreated, perfect, infinite, eternal, unchanging, independent, omniscient, and omnipotent substance.

• Mind (Finite Thinking Substance)

  A finite and imperfect substance (a thinking thing, a mind, a reason), dependent on God.

• World (Finite Extended Substance / Matter)

  A finite and imperfect substance (an extended thing), dependent on God, i.e., created.