descarte' s cogito ergo sum

D. Descartes' Life

* Born 1596 in La Haye, France (now called "Descartes-La Haye")
* Studied classical mathematics, philosophy and theology at La Flèche. Really only interested in mathematics.
* Joined the Dutch army, basically became a musketeer
* Had a dream for a new system for the sciences and philosophy in 1619
* Left the army, did important work in mathematics and science (system of optics, Cartesian axis, etc.)
* Finally got around to writing the Meditations in 1640
* In 1649, Taken to Stockholm at the request of Queen Christina of Sweden, who wanted him to teach her philosophy
* Official story: caught pneumonia, died early the next year
* Unofficial story: got caught up in court intrigue and was assassinated

II. Descartes' Vision for a New Philosophy

A. Wanted a philosophy modeled on mathematics

* All other disciplines full of controversy and uncertainty, yet no one doubts that 2+2=4
* Admired the axiomatic method of Euclidian geometry, where there was a small set of fundamental truths from which everything else is deduced
* Focus on systematic proofs -- like those you had to do in high school -- where you started with a set of premises and carefully proved things using simple deductively valid steps of reasoning. Try to eliminate any possibility of error.
* Thought this would once and for all allow for precision in philosophy and for final certainty to be reached

B. Project of the Meditations

* Realized that he previously had believed a lot of false things. Wanted to "wipe the slate clean", so-to-speak.
* He put it off for so long since it seemed like such a difficult project.
* Meditation One: "Concerning Those Things That Can Be Called Into Doubt"-- "At last I will apply myself earnestly and unreservedly to this general demolition of my opinions."
* If there is any doubt to whether something is true, we must throw it out. Certainty of the sort possible in mathematics is only possible by starting with indubitable axioms.
* Once something is thrown out, every belief based upon it would also crumble

III. The First Meditation: Descartes's Flight Into Skepticism

Remember that Descartes wants to throw out anything that isn't certain. So he's looking for something that he can keep -- somethng he cannot doubt. In the first meditation, he seems to alternate between finding problems with his beliefs and finding glimmers of hope. But at the end of the first meditation, the problems win.

First problem: The senses are deceptive. There are optical illusions and hallucinations that trick our senses. If our senses are deceptive at all, we can never trust them completely. Therefore, we have to throw out all sensory knowledge.

First glimmer of hope: But our senses really only deceive us about small and distant things. Certainly something right in front of my face that I can perceive with a number of senses cannot be doubted, e.g., that I'm sitting here next to the fire. Maybe those things I can still believe.

Second problem: But I might be dreaming! Then I might perceive something as being right in front of my face and still be mistaken.

Second glimmer of hope: Even if I'm dreaming, I know that the general kinds of things I experience in my dreams exist. Even the bizarre monsters I experience are just composed of colors and shapes that I experience in daily life. This would mean that some sciences might be mistaken, but that mathematics is still indubitable. After all, the mathematics of triangles doesn't depend on the existence of any particular triangles anywhere... only on the essence of triangles in general.

Third problem: But God is all powerful. God could make it so that I think there is a physical world and things corresponding to the general sorts of objects I experience when there is not. In fact, God could even deceive about the truth of mathematics. Therefore, even these things can be doubted.

Third Glimmer of Hope: But God is supposed to be supremely Good. He would not deceive me, at least not all the time.

Fourth problem: But God might not exist at all. That would only make me less sure that I might not be deceived. What is worse is that instead of God, there might exist an evil genius who does everything he can do deceive me. All my experiences are mere illusions. There is no earth or heavens. I have no body. He makes me think false things about mathematics. In short, he deceives me about everything.

Conclusion of the First Meditation: Descartes has now been reduced to total skepticism. The possibility of an evil genius existing instead of God makes him doubt everything. He has yet to find anything which meets his criteria for knowledge. He gives up for the night, concluding at least that he will spite the evil demon by at least refusing the believe the false things he used to believe.

IV. The Cogito: Descartes' Fundamental Principle (Meditation II)

A. The night before Descartes was lead to utter skepticism, and is now certain only that nothing seems certain.But he has hope that if could find just one indubitable truth to cling to, he might use it as a starting place to discover more. So he starts looking for one. He had assumed that God or an evil genius was the cause of his false experiences. So he asks whether then God or the evil genius must exist in order to cause the illusions. But he concludes that it might be he himself who somehow tricks himself. But then he asks whether then he himself must be something, which leads him to his great discovery.

B. Descartes's famous saying "Cogito ergo sum." (Latin), "Je pense, donc je suis" (French) or "I think, therefore I am." (from the Discourse on Method)

* That "I exist" must be true every time I think it
* It's impossible for me to doubt that I think. It's just incoherent to say "I think I don't think." So I know I'm thinking, and if I'm thinking, there must be a "me" to do the thinking
* This one fundamental principle ("The cogito") can serve as a foundation upon which to arrive at truth

C. But what am I? I know I exist. What is my essence ?

* I used to think I was a "rational animal" or a being with a body that walks around and eats
* But all of this are uncertain. I might not be those things, but even then I would still be me. They cannot be part of my essence.
* I know I exist so long as I am thinking. What am I then, fundamentally? I am a thinking thing (res cogitans).
* I am a mind, something that doubts, understands, affirms, wills, refuses, and also imagines and senses.
* Senses? How can the "mind" sense? Don't sense organs "sense"? If the mind senses, then sensing must be a kind of thinking. Descartes admits this. I might not have any sense organs and all my sense perceptions might be false, but I can't be wrong that I at least seem to see things, that certain images are present in my mind. I can't be wrong about whether or not I have those images, only about whether they represent things outside me. So,.yes, they are like thoughts. And yes, they exist within the mind and not in the sense organs. Sense organs might not even exist!

V. The Wax: Rationalism and Substance

A. At this point, Descartes stops and thinks it's strange that the mysterious self or "I" should be better known and more certain than the things we see and feel every day. How can this be?

B. He decides to take the piece of wax as an example and considers it. What do we know about it, and importantly, how?

* By my senses, I see the color and shape of the wax, I smell its fragrance, I feel its hardness, I hear a noise when I tap it.
* But if I bring the wax close to the fire and it melts, what changes? It's not the same color, shape or size. It doesn't smell the same. It is no longer hard and no longer makes a noise when tapped.
* Now the wax still exists, but none of the attributes it had which I perceived by the senses are the same.
* Descartes' conclusion: The senses only allow us to know the accidental properties of the wax. The wax itself--the thing that exists throughout the changes--the wax as substance, is not something I know by senses. Rather, I know it by my mind or intellect.

C. What does all this mean? Everything we see and touch is most directly grasped by the mind. The mind is needed to perceive anything. So it really isn't so strange that the mind should be better known than ordinary physical things.

D. Of course, I might be wrong. My intellect may be in error. Maybe there is no wax itself, no substance "out there". But that just goes to reiterate that my mind must exist, for even if I am in error, it is me or my mind that is in error.

E. The conclusion: There is nothing better known to me than my mind . Certainly not my body or my sense organs or the attributes perceived by them.

VI. The Ontological Argument for the Existence of God

A. What we skipped

* Meditation III: Descartes's first proof of God
* Meditation IV: A discussion about whether God could be a deceiver and what is necessary in order to avoid making errors on one's own

B. First of all, why does Descartes want to prove the existence of God at this point?

* The possibility that he is controlled by an evil genius still keeps him from being sure of anything -- the physical world, mathematics
* Even the cogito is uncertain for this reason -- the evil genius might be tricking me (me?) about what seems like the clearest and distinct and most indubitable truths, even about logic itself.
* But if God existed, then since we know God is supremely good, we know that God would not deceive us about the things that we clearly and distinctly perceive or have concluded to be true by careful use of reason
* So we'd better prove that God exists, otherwise we'll always have lingering doubts

C. The Existence / Essence distinction revisted

* Descartes here talks about the idea of a triangle
* Even if there are no triangles "out there in the world", or in Aristotle's term, there are existing traingular substances, there still is an essence or form of triangles
* We can still deduce geometric truths about triangles just based on their essence or their definition. These things about the essence of a triangle would be true even if no triangles existed "out there". After all, we can deduce all sorts of truths about shapes which we've never seen in nature and probably don't exist anywhere in nature. (i.e. a 127 sided figure). The mathematics is still true.

D. The proof of the existence of God


* Descartes has an idea of God. God's essence is being a supremely perfect being.
* What's different is that this makes God's existence inseparable from his essence. A supremely perfect being must have all perfections, and something that doesn't exist lacks the perfection of existing.
* It is as contradictory to think of God without existence as it is to think of a mountain without a valley or a triangle without three sides.
* It might seem at first that we can imagine God as not existing or separate his existence from his essence, but not if we think more about God's essence. We might also at first think that there are right triangles which do not follow the Pythagorean theorem, but if we think about it, we will recognize that this is impossible.

E. Now that God has been proven to exist, Descartes can breathe a sigh of relief. Now, since God is not a deceiver, he can trust any perception he has which is clear and distinct, and he can trust his reasoning about mathematics, etc. There is no evil genius.

F. Problems

1. Problems with the ontological argument

* What is a "supremely perfect being"? Does this make any sense?
* Why is existence a perfection?
* Can we really define things into existence? Personal ad example. Perfect island example.

2. "The Cartesian Circle"

* Descartes wanted to prove that God exists so that he could trust his reasoning
* However, Descartes used reasoning to prove the existence of God
* If the evil genius was truly able to deceive him even about logic itself. then the evil genius could have tricked him about his proof for the existence of God.
* So Descartes's solution to the evil genius problem is circular. He uses reasoning to try to justify his reasoning as sound.
* Did he really have any other options?

VII. The End of Descartes' Skepticism and the Arguments for Dualism

A. Descartes has proven that whatever he clearly and distinctly perceives is true. This means

* While the senses are not to always be trusted, when they are used properly and the ideas that they furnish are clear and distinct enough, they can be a source of knowledge
* In general we can conclude that there are things out there that resemble the ideas we have from sense -- sky, earth, sea
* I also know that there is one physical thing in particular -- the body, which bears a special relation to me as a thinking thing. I cannot be separated from it. I feel certain desires and sensations, pains and hungers and excitements "on its behalf"

B. And in general, if two things are clearly and distinctly perceived to have different natures, they are different substances. This is true of the mind and the body.

* The essence of the mind is that of a thinking thing which is not extended, corporeal or divisible.
* The essence of the body is to be extended, corporeal and divisible.
* As we've seen, one can be known to exist without the other. Therefore, it is possible that they could actually exist independent of one another; hence, they are different substances.
* Still, there is a connection between them. The activities of the brain are especially correlated with the activities of the mind (although they are surely not the same thing!)
* Nerves in our body connect to our brain and when they are "pulled", not only do they cause motion in the brain, but also a sensation in the mind
* Similarly, certain acts of the mind (acts of willing) bring about "swerves" in the mechanics of the body
* This area of Descartes's thought is rather puzzling: How it possible for something immaterial to cause motion in the material world and vice-versa? Descartes doesn't tell us, but suggests it has something to do with the pineal gland.. This is not very helpful. "The problem of mind-brain interaction."

C. Finally, Desartes rids himself of the doubts considering whether he's dreaming. The images of dreams are not clear and distinct like regular experiences. Instead, they involve people appearing and disappearing, no continuity, etc. So my dream experiences are not to be trusted, but my regular experiences, which are not like this, are trustworthy.