Rene Descartes (1596-1650):
The Father of Modern Philosophy
- Rene Descartes’ Response to Skepticism
- Descartes' Accomplishments:
- Optics - How We See
- Mathematics - Cartesian Coordinate System
- Philosophy - What and How we Know
- Meditations on First Philosophy - a summary of Cartesian Philosophy
- Descartes' Project -
- Identify and eliminate false beliefs
- Demonstrate how to move from true beliefs to knowledge
- A Structural Overview of The Meditations:
- Meditation I: How to recognize true beliefs
- Meditation II: Some beliefs cannot be false
- Meditation III: Proof of the existence of God
- Meditation IV: Why do we make mistakes?
- Meditation V: The essence of things
- Meditation VI: Proof of dualism; the mind/body distinction
- Meditation I: What Can be Doubted or How to get Rid of False Beliefs
- The Problem - We grow up believing many false things, and we base other beliefs on the false ones.
- The Solution - Find a way to distinguish true from false beliefs (Methodological Skepticism)
Note: Two Necessary Conditions for an Adequate Truth Rule:
- The Truth Criterion - property appealed to must never belong to a false belief
- The Recognizability Criterion - the property appealed to must be recognizable to ordinary cognizers
Possible Truth Rules:
TR 1: Accept as true any belief that has been acquired through direct or indirect sensory experience.
Objection: Illusions and Hearsay
TR 2: Accept as true any belief that has been acquired through direct sensory experience under uniform or ideally favorable external conditions.
Objection: Insanity or Hallucinations
TR 3: Accept as true any belief that has been acquired through direct sensory experience under uniform or ideally favorable external and internal conditions.
TR 4: Accept as true any belief that has been acquired through direct sensory experience under uniform or ideally favorable external and internal conditions when one is not asleep.
Objection: We cannot distinguish between dreaming and waking
TR 5: Accept as true those general beliefs based on sense experience that are about the simple sensible objects and that are necessary in order to have the experience we have in our dreams.
- shape ("figure")
- quantity or magnitude
Objection: The Evil Demon (or brain in a vat Hypothesis)
- Meditation II: Response to the Sceptical Hypothesis
- Consequences of the Skeptical (Evil Genius) Hypothesis:
- all our sense data could be false
- all our memories could be false
- there might be no external universe
- Necessary existence of the self Cogito Ergo Sum: Thinking requires a thinker
Even if there is an Evil Genius who deceives me about everything else, there
must be an 'I' to be deceived. Either I am deceived and I exist, or I am not
deceived and I exist. Therefore, I must exist (or, even if I can doubt all
else, I cannot doubt that I exist).
- 'I' refers to the thinker (whatever it is that is thinking)
- If there is thinking, there is a thinker.
- I am a thinking thing (the substance of the soul is thought)
- Representationalism - The TV Screen Theory of Perception
- Meditation III: How God Secures our Knowledge
TR 6: Accept as true every belief that is clearly and distinctly believed
Question: Does this rule meet the necessary conditions for a TR?
- Evaluation of TR 6:
- Can we recognize clear and distinct Ideas?
- Are clear and distinct Ideas True?
YES, if and only if
- God exists, and
- God is not a deceiver
- Descartes' Argument for the Existence of God
- Three kinds of Ideas in the mind:
- Innate (those I discover within myself)
- Adventitious (those I get accidentally)
- Invented (those I create for myself)
- Theory of Perception - Representationalism (the TV screen theory)
- Descartes’ Ontological Hierarchy -
- Formal Reality - common to all existing things
- Objective Reality - belongs to things which represent other things
- The Argument for God's Existence:
- P1) I have an idea of God;
- P2) The idea 'God' is of a perfect being.
- P3) the cause of the idea must have an equal or greater amount of formal reality than the idea has
- P4) The idea 'God' has more objective reality than I have formal reality
- Conclusion 1) Therefore, I am not the cause of my idea of 'God'
- P5) Since I am not the cause of my idea 'God' there must be some cause of it outside myself.
- P6) Only a being with perfect formal reality could cause the idea of a perfect being in my mind.
- Conclusion 2) Therefore, God, the perfect being, exists outside my mind.
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