Lectures: Descartes

I. Historical Background and Biographical Information

A. In the 2000 years or so between Aristotle's death and the early 17th century, with the exception of theology, philosophy remained largely unchanged in Europe

B. The 16th century (1500s)

C. The early 17th century

D. Descartes' Life

II. Descartes' Vision for a New Philosophy

A. Wanted a philosophy modeled on mathematics

B. Project of the Meditations

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)

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

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?

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

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

C. The Existence / Essence distinction revisted

D. The proof of the existence of God

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

2. "The Cartesian Circle"

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

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.

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.

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