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I. Epistemological Theories:

Skepticism: we cannot know anything for certain. If there are absolute truths, we do not have access to them.
Relativism: there are no absolute, certain truths. Knowledge is always a matter of (cultural or individual) perspective.
Rationalism: reason is the primary source of all knowledge, superior to sense evidence. Only reason can distinguish reality from illusion and give meaning to experience.
Empiricism: all knowledge ultimately derives from sense experience, and all meaningful ideas can be traced to sense data.
II. DESCARTES: a rationalist
The method of doubt:
“Reason now leads me to think that I should hold back my assent from opinions which are not completely certain and indubitable just as carefully as I do from those which are patently false. So, for the purpose of rejecting all my opinions, it will be enough if I find in each of them at least some reason for doubt. And to do this I will not need to run through them all individually, which would be an endless task. Once the foundations of a building are undermined, anything built on them collapses on its own accord; so I will go straight for the basic principles on which all my former beliefs rested.”
1. What is the goal of doubt for Descartes? (252)
2. What is the actual method? (253. 1st column, bottom. note: a method is the steps one takes to accomplish something.
An opinion is a proposition that one holds to be true - a belief. Taking any given opinion, what will Descartes ask himself?)
Which of the following beliefs do you think passes the method of doubt test? How are these beliefs different?
§ 1. I am in the classroom now
§ 2. I am having the experience of being in the classroom now
This gives us a very strict standard for knowledge. Why did Descartes think he needed it? [250. Note that "certainty" is really a logical property here, which could be seen as "capable of being doubted" not psychologically (in our actual thoughts) but logically (philosophically/metaphysically). In other words, uncertain beliefs are "doubtable" but not necessarily "doubtful" - as in improbable. It is certainly probable that you are reading this. Is it doubtable?]
In the three stages of doubt, Descartes applies his method. In each case, he finds some reason to doubt his belief, so he decides he must withhold his assent to the truth of the belief. See page 253 for the three groups of beliefs that come into doubt.
1. The argument from illusion
Most knowledge seems to come through the senses, but sometimes our senses deceive us.
§ how is this a use of the method of doubt?
§ what lesson can we draw from this argument (what is the extent of the doubt created?)
§ what is the common-sense reply?
§ how does this lead to the next stage of doubt
2. The argument from dreams
Morpheus in The Matrix: “Did you ever have a dream you were so sure was real?” [He means: true. Of course the dream is ‘real’ in some sense. But it is false in the sense that a dream is an experience caused by something other than what is actually being experienced.]
How does Descartes’ dreaming argument go? (253, 2nd column)
How is it a use of the method? (note: there are many opnions here, but all about a particular type of belief)
What is his conclusion? (what class/type of belief is doubtable?)
So far, many, but not all, types of beliefs have been called into question. Which types of beliefs are affected and which are not? Why?
A priori truths: known “prior” to experience. Example: mathematical truths
A posteriori truths: those that rely on experience for verification. Example: elephants are gray.
How does this distinction drive us to the third stage of doubt? (See Lawhead p. 253)
3. The evil genius
What is the point here? Does Descartes “believe in” an evil genius?
How is this a use of the method?
What additional beliefs are in question now?

In this use of the method, Descartes finds something that he can discover no reason to doubt, so it must be true
Suppose an evil genius is deceiving me. Then I must exist [to be deceived.]
So, we turn the skeptic’s argument against him:
1. The skeptic agrees that we’re in doubt.
2. I am doubting.
3. Therefore, I must exist.
Use the method of doubt here: try to doubt that you exist. The act of doubting your existence confirms it. So, since doubting is a kind of thinking, “I am, I exist, is necessarily true whenever it is put forward by me or conceived in my mind.”
The ‘self’ (you: the seat of your own experience) after this argument:
What am I after the cogito argument? I exist as a thinking thing (a mind.) But a mind is not necessarily the same thing as a brain. I am not yet sure that I am a physical being at all. All I know for certain is my thoughts. This is the problem of solipsism. (255) Solipsism is the view that there is no reality outside one’s own mind. Descartes spends the next three chapters of his book trying to retire this worry. We will pick him up again after he has argued that the external world exists and that he does in fact have a body.
Making a long story short:
Descartes is not a solipsist or a skeptic! He does believe we can know the world outside our own minds, and that he can prove its existence using mathematical proofs as a model. In other words, he thinks that our (correct) beliefs about abstract objects (the self, triangles, God - as a concept) are the most certain. Using these, he 'proves' the existence of the external world and consequently of our bodies - see p. 259-60. (Hume will call his proofs into question.)
At the end of the Meditations, Descartes claimed to have proved that we are a close “union” of two distinct substances* - a mind coupled to a body.
His argument for the “real distinction” between mind and body (as substances.)
1. Body is divisible into parts
2. Mind is not divisible
3. Two things which have different essential properties (like divisibility) must be truly distinct sorts of things
4. Therefore, mind and body are distinct (different) substances
Can you see any problems with this argument?
Thomas Hobbes saw problems with Descartes’ arguments. For Hobbes, all reality is simply “bodies in motion” including human thought. So no mind-body distinction for him! See Lawhead pp. 241-43. The film clip on Hobbes and materialism (the view that all reality is physical) presents one of his arguments. Do you see any problems for it?
*substance: this is an older concept, used by philosophers from Aristotle (4th century BC) to the 18th century (up to about the time of Hume, but not anymore.) A substance is an entity that can stand on its own, is not dependent on another thing for its existence (except maybe for a dependence on God.) For instance, properties (redness, etc.) depend on objects for their existence. (Redness doesn’t exist independently – it exists in red things.) So a substance is something that has properties but is not itself a property. See the glossary in Lawhead.
IV. HUME: an empiricist, and a skeptic
1. Classification of mental items according to Descartes, Hume:
Hume reverses Descartes' hierarchy of mental items. To see this, we must understand what he means by an impression and by an idea.
1. What are impressions, for Hume? (336)
2. What are ideas?
For Descartes, abstract ideas are best for knowledge, because they contain no sensory data that could confuse/obscure them. So why does Hume think ideas are worse for knowledge than impressions? (336, 2nd column, bottom)
2. Two kinds of Inquiry (337-8)
type of inquiry
objects of knowledge
relations of ideas
math and logic
matters of fact
the external world, physics, etc.
3. The Empirical Criterion (339, 1st column)
How do we use ideas carefully? See especially the quoted passage in the middle of the page!!
Hume attacks the cherished metaphysical ideas of the rationalists:
1. Substance (339) For Descartes, we are the union of two different substances: mind and body. A substance can be thought of as a thing that has properties but is not itself a property. (A rock is hard, gray, solid, angular in shape, etc. But what is this 'thing' that has these properties?)
What is Hume’s attack here? How does it rely on the empirical criterion?
2. The self: (the knowing subject; 340)
What is Hume’s attack here? How does it rely on the empirical criterion?
3. Causality (340-42)
What are the three phenomena you experience when you conclude that A caused B?
How does Hume use the empirical criterion to raise skeptical doubts about cause and effect? (341)
How does he respond to the objection that some regularities are just too “regular?” (See the Hume pdf and the cartoon: the problem here is the problem of induction.)
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