Introduction

Descartes' Methodology

• Logic's Reduction Method
• Descartes' Method of Hyperbolic Doubt
• Description of his Method
• Why his Method is called the "V" Method.

Synopsis of the Meditations

1 & 2:  Argument for Doubting Senses and Necessary Propositions

Cogito Ergo Sum

3:  Cosmological Argument for God

5:  Ontological Argument for God

6:  Putting the World Back Together

• Three Types of Ideas
• Thinking, Thoughts and Thinkers
• Reality

Logic's Reduction Method

Descartes' Method of Doubt

1. Only accept Certainties.  (Things that are clear, indubitable and distinct).
2. Divide everything into smaller parts and then analyze.
3. Be orderly and systematic about your technique.
4. Be complete and check your work.

Description of his Method:

1. Must be Universal
2. Must be Methodical (to the end of Certainty)
3. Must be Provisional
4. Must be Theoretical (Part of Philosophy, not daily life)
5. Must be Rational

Descartes' "v" Method

1. Doubt, Analyze, and break everything into parts.  (The "\ " part of the V )
2. At one point, you will hit rock bottom and there is nothing more you can doubt.  Hopefully, there will be something that it indubitable. (The " . " part of the V")
3. You can use this indubitable belief (you found in #2) as a foundation to prove other beliefs that you had doubted before.  (The " /" part of the V).

The 6 Meditations

1. Why We can Doubt Everything.
2. Doubt Everything and Discover that the mind is the only indubitable thing.
3. The Cosmological Proof for the Existence of God.
4. Everything that is Indubitable is True (not a very exciting Meditation).
5. The Ontological Proof for the Existence of God.
6. Use God and our Existence to "undoubt" everything.  Discuss Understanding vs Imagination.

Meditation 1 & 2: Why Doubt?

• The Senses can Lie!
• Most of our Knowledge is from our Senses.... but the senses can't be trusted, so we must doubt all sensory impressions.
• Example:  I see a man 3 blocks away.  He looks like he is about 3 inches tall.... but I know he is not.  Thus, my senses are lying to me and I can't always trust my senses.
• I may be Dreaming!
• I have had dreams that seem very real to me.  I thing I am in a field of grass watching the sunrise, when I am really sleeping in bed.  I have no way of telling whether or not I am asleep, so I can't trust my senses.
• But:  Regardless of whether or not I am dreaming and whether or not a distant man is 3 inches tall.... there are some things that will always be true.  1+1 will always equal 2.  Every time I put 1 chair next to another, I always see 2 chairs.
• There may be an Evil Genius!
• My brain may be in a vat and some Evil Genius may be feeding me misinformation.
• Maybe 1+1 actually equals 3, but the Evil Genius always tricks me into believing 1+1=2.  (Every time I put 1 chair next to another, I always see 2 chairs.... but I may be seeing 2 chairs because the Evil Genius is tricking me!)
• Since I don't know if the evil genius exists or doesn't, I can't trust Necessary Propositions until I find out.  (Necessary Propositions are statements that are true by definition such as 1+1=2 and other Mathematical Truths.)
• Thus, I can't trust my Senses or Necessary Propositions because of these 3 reasons.

Cogito Ergo Sum

• After Descartes' Hyperbolic Doubt, I can't trust my own senses or necessary propositions.  Things are looking pretty dismal... but....
• No matter how hard I try, I can't ever doubt my existence!!  "I think, therefor I am."
• Every time I try to doubt "I am; I exist"... I prove my own existence by thinking "I am; I exist".
• I have finally found something that is indubitable:  me.

3rd Meditation: Proof of God

1. Everything that exists has a cause.
2. The cause of a thing must have as much (or more) reality than its effect.
3. I have an idea of a being with infinite formal reality.
4. My idea of that being must have a cause.
5. My idea of such a being cannot come from myself, nor can it be cause by any of my other ideas (aka made up)
6. The outside cause of this idea must have as much formal reality as the idea has objective reality.
7. Since my idea includes (in its objective reality) the notion of infinite formal reality, then the cause of my idea must have infinite formal reality.
8. Therefor, a being with infinite formal reality must exist.
9. Therefor, God Exists.

5th Meditation:  Proof of God

1. If I have an idea of something..... then anything that I clearly and distinctly perceive as being an essential property of that thing, is actually a property of that thing.
2. I have an idea of God, the supremely perfect being.
3. Therefor, that which I clearly and distinctly perceive to be an essential property of God is a property of God.
4. I clearly and distinctly perceive actual and eternal existence to be an essential property of God.
5. Therefor, actual and eternal existence is a property of God.
6. Therefor, God Exists.

6th Meditation:  Putting the World Back Together

• Getting Necessary Propositions Back...
• Since God exists, we know that there is no Evil Genius.  (There can only be one "God-like" being, and that is God... so there is no Evil Genius.)
• God would not trick us, so we don't have to worry about God being the Evil Genius theory.
• Since the Evil Genius no longer exists, we can once again trust Necessary Propositions.
• Getting the Physical World Back...
• We exist as thinkers.
• Our ideas exist.
• We have "a strong inclination to believe" our idea of locomotion.
• We can't have an effect without an equal or greater cause.
• So, we need something that caused the idea of locomotion.
• Obviously, locomotion in the physical, extended world caused our idea of locomotion.
• You can't have locomotion without extended substances to locomote.... so the extended world exists.

Three Types of Ideas

Thinking implies Thinkers and Thoughts

                         Thinking
            ----------------|---------------
            |                               |
         Thinker                       Thoughts
            |                               |
   -----------------                     Ideas
   |               |                        |
 Soul            Body          --------------------------
(Thinking)    (Extended)       |            |           |
                           Fictitious    Innate    Adventitious
                           (from Us)   (from God)  (from Senses)
 

How do Thoughts and Ideas differ?
  Ideas are like mental images.
  Thoughts = Ideas + a Mental Activity.

Thinking implies the existence of both Thinkers and Thoughts.

Reality

Descartes' Reality Proposition:
If A created B, then A must have more reality than B.

Example:
Idea1:  I see a sign with Pegasus on it.  (It's adventitious because it came from the senses.  It has formal reality because the sign physically exists)
Idea1 causes Idea2.
Idea2 causes Idea3, the idea of Pegasus.

Idea3 was created by Idea2 which was created by Idea1.  Thus, since Idea1 created Idea3, Idea1 (the Sign) must have more reality than Idea3 (the idea of Pegasus).
Idea 3 has less formal reality since Pegasus does not physically exist.