Descartes's Meditation III

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Descartes Review of Meditation II

• He is certain that he exists and is a thinking thing
• What is it to be certain? "...As a general rule, everything I very clearly and distinctly perceive is true."
• But isn't it clear that, for example, the Earth exists? NO: the image is clear, but the judgment that the image corresponds to something outside him is not clear and distinct.
• What about geometry and math? These are clear and distinct, but he supposed that he could be deceived about them by the evil genius
• Thus, Descartes needs to settle the questions: Does God exists? Is God benign?

Descartes Proof of the Existence of God

• Descartes begins his proof with a mental taxonomy: there are ideas, and there are judgments.
• Only judgments can be true or false.
• What about ideas that appear to come from outside of me?
  • For any effect, there must be as much reality (positive properties) in the cause as there are in that effect.
  • Ideas may not correspond to something outside of me, but their cause must contain as much reality as the thing they are ideas of
• I have an idea of God as the most real thing
• The source of this idea of God must be at least as real as God
• The thing at least as real as the most real thing is the most real thing
• God is the cause of my idea of God
• God exists
• Could I be God, and cause this idea in myself? No: I learn things, but the idea of God is that God knows everything
• Where did the idea of God come from? God put it into me - it is innate
• Probably, God is not a deceiver (BUT: what must Descartes now explain?)

The Argument in Sum

1. For any effect, there must be as much reality (positive properties) in the cause as there are in that effect
2. Ideas may fail to correspond to something outside of me, but their cause must contain as much reality as the thing they are ideas of
3. I have an idea of God as the most real thing
4. The source of this idea of God must be at least as real as God
5. The thing at least as real as the most real thing is the most real thing
6. God is the cause of my idea of God
7. God exists