1. Introduction to Philosophy Lecture 6 Descartes
By David Kelsey

2. The Copernican Revolution
Begun by Copernicus ( ). Published De Revolutionibus in 1543.
Prior to Copernicus, Ptolemy’s Geocentric theory was dominant. It held that the Earth was the center of a multisphere universe.
Copernicus takes a mathematical approach to interpreting the movements in the heavens.
His Heliocentric view

3. Ptolemy’s theory

4. The Church’s response to Galileo & the Copernican Revolution
In 1616: Galileo ordered by the court to not defend the Heliocentric view
In 1632 Galileo publishes Dialogue Concerning the Two Chief World Systems
In 1633 Galileo was was found guilty of holding and defending the heliocentric view.
In 1633 the Church prohibits any teachings or holdings of the heliocentric view

5. Descartes Rene Descartes: lived from 1596-1650.
Was an important mathematician, physicist and philosopher.
Considered to be the father of modern philosophy
His Meditations are one of the most influential works in all of philosophy.

6. Descartes response to Galileo
In 1633 Descartes is set to publish his mathematical treatment of nature, called a Treatise on the World, when he hears of Galileo’s condemnation.
Descartes then becomes interested in epistemology because he is afraid of being persecuted for his scientific views.

7. Skepticism Global vs. Local Skepticism
Global skepticism Is motivated by the fact that things may not appear as they really are and that the true nature of things is indeterminable
The senses can deceive us..
The sense organs of animals differ from species to species
Human preferences vary from individual to individual
So we must suspend judgment
We neither affirm nor deny any belief about the real nature of an object

8. Descartes method of doubt
Descartes project: refute the global skeptic
Descartes tries to make up the most powerful skeptical arguments he can, and then he goes about trying to refute them.
This is his Cartesian method of doubt.
Cartesian method of doubt:
Early in the meditations Descartes uses two powerful skeptical arguments to show that he can doubt any of his beliefs.
But by the end of his meditations he comes to realize you cannot doubt most things.
His method of doubt is temporary.
The reason for his doubting all his beliefs is to show he needn’t doubt any of them!
He develops two powerful skeptical arguments in order to try and show them unsound.

9. Two arguments for skepticism
The first Meditation:
In the 1st meditation Descartes gives two very powerful skeptical arguments:
The Skeptical arguments:
The dream argument
The evil demon argument
Remember, he gives these arguments so that he can later refute them.

10. The Dream argument Skeptical Scenario: The argument:
If you’re dreaming right now, you’re not in a philosophy lecture you’re at home in bed.
But, for all you can tell, you might be dreaming that you’re in a lecture.
The argument:
1. If I don’t know that I’m not dreaming, then I don’t know that I’m in a lecture.
2. I don’t know that I’m not dreaming.
3. Thus, I don’t know that I’m in a lecture.
Notice that this argument tries to show that you don’t know that you’re in a philosophy lecture right now.
But, of course, it can be used to cast doubt on lots of other beliefs.

11. The Dream skeptical scenario
The dream argument assumes the dream skeptical scenario:
Skeptical scenario:
a situation in which all your evidence is as it actually is, but your beliefs turn out to be false.
The skeptical scenario presented here:
You are at home in bed dreaming.
Is incompatible with something you take yourself to know…

12. The evil demon argument
The Evil Demon skeptical scenario:
Suppose there were an evil demon who is causing you to vividly hallucinate all your experiences.
The evil demon could also cause you to have false beliefs, and to mistake invalid arguments for valid ones.
The evil demon Argument:
1. If I don’t know that I’m not a victim of an evil demon, then I don’t know that I’m in a lecture.
2. I don’t know that I’m not a victim of an evil demon.
3. Thus, I don’t know that I’m in a lecture.

13. The evil demon argument
is more powerful than the dream argument:
The evil demon can give you experiences as vivid and consistent as any veridical experience.
The evil demon can deceive you even about things that aren’t to do with your experiences.
Other skeptical scenarios not discussed by Descartes:
The Matrix
Inception
Truman Show
Brain in a Vat

14. What’s the skeptic up to?
What is the aim of a skeptical argument anyway?
The aim of a skeptical argument isn’t to show that the skeptical scenario is really true.
The skeptic wants you to grant that the skeptical scenario is merely possible.
And if we can grant that the scenario is possible then we doubt the truth of our beliefs and if we doubt then we don’t know.

15. How can we reply to the skeptical arguments?
Possible replies to the skeptic:
We could embrace skepticism.
We could deny premise 1 of the argument…
Maybe knowledge doesn’t take complete lack of doubt…
We could deny premise 2 of the argument.
Descartes tries to do this by adopting Foundationalism

16. Foundationalism
Descartes aims to deny premise 2 of the skeptical argument, that I don’t know I’m not a victim of the Evil demon. He does so with Foundationalism.
According to Foundationalists:
Every justified belief is ultimately justified by basic beliefs. A basic belief is a belief not justified by another belief, and upon which other non-basic beliefs are justified.
Thus, if you can find a way to show that the basic beliefs are skeptic-proof, you can make all the rest of the beliefs skeptic proof as well.
Foundationalists think that knowledge is like a building:
At the bottom is the foundation-the basic beliefs…
Built on them, the beliefs that directly justify others…
And built on them, further beliefs still

17. Foundationalism: refuting the skeptic
The Foundationalist has to do two things to refute the skeptical arguments:
1-Tell us which beliefs are basic and show that they are beyond skeptical doubt.
2-Show how the non-basic beliefs are justified by the basic ones.

18. The Cogito
The Cogito:
Descartes thinks that even the evil demon couldn’t deceive him about whether he (Descartes) exists.
“If there is a deceiver…then surely I exist, since I am deceived”
Descartes famous slogan:
‘I think, therefore I am’.
In Latin, ‘Cogito ergo sum’.

19. Deception presupposes a Deceived
Deception presupposes an I that is being deceived:
As Descartes says: So let the evil demon deceive me about my thoughts and in this case all of my thoughts are false. But if the evil demon can deceive me then there must be an ‘I’ that is being deceived. Thus, this ‘I’ exists.

20. The Cogito: the guarantee of truth
The truth of the belief ‘I exist’ is only guaranteed while you are thinking.
I exist so long as I am thinking.
“I am, I exist-that is certain. But for how long? For as long as I am thinking. For it could be that were I totally to cease from thinking, I should totally cease to exist.” (Meditation II)

21. The Cogito as a self justifying basic belief
According to Descartes, ‘I exist’ is a basic belief.
So ‘I exist’ is immune to doubt.
Not even the evil demon could deceive Descartes about this belief.
You can know the cogito is true just by thinking on the cogito itself.
So it cannot be doubted for it is self justifying.

22. Counterargument against the Cogito
1. Does anyone exist at all?
If I can doubt the existence of Descartes and he can doubt my existence then how can we know anyone exists at all?
But Descartes replies: It’s ‘I exist’ that’s skeptic proof.
2. There’s nothing special about the cogito.
It’s no more nor less sound than this argument:
1. I am walking.
2. Therefore, I exist.
Descartes reply: ‘I am walking’ is not a self-justifying belief.
3. Couldn’t the evil demon create a thought without a thinker?
Descartes thinks not but it seems then that his cogito is justified by this belief…

23. Descartes and the justification of non-basic beliefs
Descartes would himself agree that the cogito alone is too narrow a basis for the whole of our knowledge.
In fact, Descartes thinks he has two basic beliefs:
‘I exist’
He gets this from the cogito
‘God exists’
He gets this from several arguments which we will now look at…

24. Solipsism
Solipsism:
Note that Descartes seems to also want to show that God exists to show that he is not alone in the world. This is the view known as Solipsism.
Solipsism is the view that for each person he can merely state “I am the only thing that actually (formally) exists; everything else is only real for me.”
“If I can be sure that the subjective reality of one of my ideas is so great that it isn’t in me either formally or eminently and hence that I cannot be the cause of that idea, I can infer that I am not alone in the world--that there exists something else that is the cause of the idea. But if I can find no such idea in me, I will have no argument at all for the existence of anything other than me…”(Med. III)

25. Descartes arguments for God’s existence
In the 3rd Meditation, Descartes gives 2 arguments for God’s existence. Here is the first:
1. I have an idea of an infinitely perfect substance.
2. Such an idea must have a cause.
3. Nothing comes from nothing
4. The cause of an idea must have at least as much formal reality as there is subjective reality in the idea. (from 2 & 3)
5. I am a substance who is not infinitely perfect.
6. I could not be the cause of this idea. (from 1, 4 & 5)
7. So there must be a formal reality that is an infinitely perfect substance (from 1, 4 & 6)
8. So God exists (from 7)

26. Formal and subjective reality
Premise 4 of Descartes argument assumes the notions of formal and subjective reality:
Formal Reality:
Something has formal reality if it actually exists.
So an idea of an object represents the object and so both the idea and the object have formal reality of their own.
Subjective Reality:
When you entertain an idea your thoughts have subjective reality: reality for you.
Some objects have only subjective reality: the tooth fairy…

27. The Best Counterargument to Descartes argument
Couldn’t man have created the idea of God?
Descartes argues that the idea of God could not have come from man because everything in the idea of God, a perfect idea, must be in the cause of it and yet man isn’t perfect.
This is supposed to follow from the idea that something cannot come from nothing.
But consider the power of imagination. Is it possible that the imagination is perfect enough to create the idea of God?
Descartes response: “we cannot grasp the infinite from the finite because there is more reality in the infinite than in a finite substance and hence that my grasp of the infinite must somehow be prior to my grasp of the finite--my understanding of God prior to my understanding of myself.”
Counter: don’t we learn the simplest then the complex?

28. Descartes 3rd argument for God’s existence: the Ontological Argument
Descartes’ version of the Ontological argument:
Comes in the Meditation V
1. God, by definition, is a being of infinite perfection
2. Existence is a perfection (a being wouldn’t be perfect if it lacked existence.)
3. Thus, God exists.
Evaluating the argument:
Questioning premise 2: Is existence a property?
Defining God into existence
The lost island

29. God’s existence justifying the non-basic beliefs
God wouldn’t allow me to be deceived:
Descartes thinks God wouldn’t allow me to be radically mistaken about the nature of the world.
So God wouldn’t allow me to be deceived by an evil demon.
So the skeptical scenario’s cannot cast doubt on my beliefs.
Thus, my belief that God exists justifies lots of my other beliefs.

30. Where does Descartes go now?
Problems for Descartes:
Descartes attempt at justifying all the non-basic beliefs is dubious:
Few people think that the ontological argument is sound.
And his other arguments for God’s existence are problematic.
And Descartes says that the evil demon could fool him into thinking bad arguments are really good ones.
Replies for Descartes:
Maybe one of his arguments for God’s existence is defensible…

31. Descartes criterion for truth
The Cogito is the basis for Descartes’ criterion for truth. He first introduces his criterion in Meditation III.
Descartes knows the cogito. He knows it with certainty. He takes this knowledge as a model by which to judge other beliefs.
1. Descartes is certain that he exists as a thinking thing.
2. Descartes asks himself, What is it about this proposition that accounts for my certainty that it is true?
3. His answer: the fact that I grasp it so clearly and distinctly that I perceive it could not possibly be false.
4. He concludes: let this be the criterion: whatever I grasp with like clarity and distinctness must also be true.

32. The Criterion: clear and distinct perceptions
So Descartes holds that anything which he perceives clearly and distinctly is true. The perception must be as clear and distinct as the way in which he perceives the cogito.
For a belief to be clear:
something is clear when it is “present and apparent to an attentive mind, in the same way as we assert that we see objects clearly when, being present to the regarding eye, they operate upon it with sufficient strength.” (Principles of Philosophy, 1.45)
We don’t accept beliefs that are fuzzy, obscure, dim, vague, indefinite, indistinct, etc.
For a belief to be distinct:
Distinct: “so precise and different from all other objects that it contains within itself nothing but what is clear”.
It must be impossible to confuse the idea with any other idea
Triangle example…

33. Final thoughts on Descartes
Can he escape the worries of his arguments for God’s existence?
How do you find the cogito?
Is Descartes criterion for truth sensible? Is a worry created here because of the doubts associated with sense perception?