Lecture on Rene Descartes' Philosophy

Radical Skepticism and Foundational Belief

• Descartes uses radical skepticism to find a foundational belief that is absolutely certain.
• Discovers the truth: Cogito, ergo sum (I think, therefore I am).
  • Even if deceived, there's an 'I' being deceived.
  • This belief is indubitable.

Beyond the Cogito

• Descartes needs to explain how beliefs from senses and mathematics are rational.
• Seeks a bridge from the foundational truth (Cogito) to other beliefs.

The Bridge to Rationality: Argument for God's Existence

• Descartes presents an argument for God's existence.
  • Not to promote religion, but to explain belief reliability.
  • Uses belief in God to justify belief-forming mechanisms.

Descartes' Argument for the Existence of God

1. Innate Idea of God: We have an idea of a most perfect being (infinite substance).
2. Descartes claims:
   • This idea can't come from us or the imperfect world.
   • Cause must have as much reality as the effect (cause of perfect being idea must be perfect itself).
3. Conclusion: An infinite and perfect being (God) must exist.

Implications for Knowledge

• God's Perfection: God cannot deceive.
• Therefore, belief-forming mechanisms are reliable if used correctly (perception, calculation).
• Deductive Argument:
  1. If God is perfect, my belief-forming mechanisms are reliable.
  2. If mechanisms are reliable, I am justified in my beliefs.
  3. Conclusion: If God is perfect, I am justified in my beliefs about reality.

Criticisms of Descartes' Argument

• Cartesian Circle: Potential fallacy of begging the question.
  • Descartes' argument assumes what it later tries to prove.
  • Intellect must be trusted to prove God's existence, but God's existence is needed to trust intellect.

Note: These points summarize Descartes' approach and the critique he faces.