My personal view of history is summed up in the phrase "avalanche
theory." If you have ever wondered why the modern world has the shape
it does, consider the following metaphor. Imagine a mass of snow and
ice perched at the top of a mountain. Just below this mass, there is a
charming and harmonious forest. Below that, there is a perfectly
organized village, consisting of excellent houses, wonderful factories,
schools, hospitals, restaurants and several very nice pubs. Then comes
the avalanche. This huge mass of snow and ice carries the forest into
the village, mixes everything up and strews everything randomly across
the lower hillsides. Now imagine that you are walking across the
aftermath, and you see a duck sitting in a chamberpot. You imagine it
must have a good reason for sitting in the chamberpot, but when you
ask, the duck begins her explanation with "well, there was this
avalanche, see..."
René Descartes did not set out to write philosophy. He set out to write
an astronomy text, but there was this avalanche.......
To understand Descartes's situation, you have to understand church
politics at the time of the Reformation. The Catholic church dominated
Europe in much the same way that radical Islam dominates many middle
eastern and African countries today. Europeans tended to accept church
authority because they believed that human dignity was dependent, not
on individual achievement, but on being some kind of cog in the
machinery of a great plan being carried out by some very powerful other
individual. People thought that their lives could only have meaning if
they were playing some part in god's plan for the universe. Since the
church was thought to be god's plan in action, supporting the meaning
of one's own life meant supporting the church. From the church's
perspective, anything that threatened the perceived connection between
human dignity and god also threatened the church's ability to carry out
gods plan. Basically, the vast majority of churchmen believed, one way
or another, that anything that criticized the church's view of reality
threatened the church's ability to save the souls of the human race.
And they could get really nasty about stuff like that.
The biggest support that the church had was the belief that the Earth
was the center of the universe. The main argument for the existence of
god at that time was the centrality of the Earth in the universe. As
far as anybody could tell, absolutely everything else revolved around
the Earth, making the Earth the exact center of the universe. It was
held that this fact could only be explained if we assumed that some
powerful being had created the universe purely as a place in which to
put human beings. This argument made sense to just about everybody at
the time and, not unreasonably, it was heavily promoted by the church.
Enter Galileo. Well, not exactly. Galileo could actually have announced
his discovery in a way that avoided problems with the church. He had
allies and supporters who were willing to defend him, and he had
available to him a way of presenting his results that would have
allowed the church to go on saying that the Earth was the center of the
universe. Galileo had an option that is not available to modern
thinkers. Medieval thinkers had a way of reconciling contradictory
beliefs by saying that one belief is true, and then the other merely
appears to be true. This was known as "saving the appearances," and it
had kept a lot of people out of trouble with the church. It probably
would have worked for Galileo too. He could have announced his
discovery of the moons of Jupiter, announced that they appeared as if
they revolved around Jupiter but, of course, in reality, everything
revolves around the Earth. He could have introduced his model of the
solar system, in which almost everything revolves around the Sun, and
everything else revolves around things that revolve around the Sun, and
gotten away with it if he had simply said "if we think about it this
way, it makes the appearances come out right. But it's just an
imaginary model to make calculations easier. In actual fact, as we
already know, everything in the universe revolves around the Earth."
But Galileo didn't do that. Galileo didn't try to avoid trouble by
"saving the appearances." Galileo said simply that this was the way it
was. And this is one of the most important things about Galileo. He
represents what for many people was a radically new way of thinking.
One of the most important parts of the development of thought is the
stripping away of bad ways of thinking and, by his refusal to save the
appearances, Galileo made that way of thinking much less intellectually
respectable. Of course, he paid a price for this, and so did other
people. After Galileo's trial and punishment, the anti-scientific
elements of the church were much more active, and it became much more
dangerous to do the kind of astronomy that seemed to conflict with
church doctrine.
And Descartes wanted to do the kind of astronomy that conflicted with
church doctrine. He accepted the Copernican model of the heavens, and
he wanted to write a book saying so. I don't think that Descartes was
worried about being punished so much as worried about the apparent
conflict between religion and philosophy. I think he saw that the new
astronomy demolished the old picture of the Earth at the center of the
universe, and that this meant that the church's main argument for the
existence of god was vanishing into thin air, but he also thought that
there were other philosophical ways to prove the existence of god. I
think he thought that if he could show that philosophy was not only
compatible with religion, but actually supported it, he would not only
shore up the church's position, but also make the world safe for
philosophy.
And once the world was safe for philosophy, he would be able to sit
down and write that astronomy book.
Descartes's Method.
Descartes was a mathematician, and he was probably very comfortable
with the rigorous reasoning needed to do serious work in mathematics.
When Descartes turned to philosophy, he did not find the kind of
rigorous reasoning he was used to. In fact, philosophy was a mess.
Mathematicians like to derive things from first principles, and
Descartes didn't see anyone in philosophy who had done anything like
this. So he set out to rebuild philosophy from the ground up with the
same kind of foundation and rigor as mathematics.
In one respect, Descartes' philosophical method was very much like
mathematics. But in another respect, Descartes' philosophical method
was very much unlike mathematics.
The way that Descartes' method was like mathematics was that he tried
to do the same kind of step-by-step reasoning that mathematicians do.
In mathematics, a thinker basically starts with some set of
propositions, such as "parallel lines never meet," and then tries to
logically deduce other propositions from that first set."Deduce" is a
special word. When one proposition is "deduced" from another, that
means that the second proposition cannot possibly be false unless the
first proposition is also false. This means that, if the first
proposition is true, the second proposition absolutely has to be true
too. This means that, once you prove something in this way, that new
thing you have proved can be used to prove other things. Plane geometry
is like this. It starts with a small set of "axioms," or statements
that are just assumed to be true, and goes on to deduce things from
those axioms, and then other things from those things, until a whole
bunch of stuff has been proved, all of it following from the original
axioms. The first interesting thing about this is that, if those axioms
are true, absolutely everything deduced from them must also be true.
The second interesting thing about plane geometry is that the axioms
themselves have not been proved. They are just assumed. And this is how
Descartes' philosophical method is different from mathematics. He did
not want to start off by assuming anything. He wanted to start off with
something that had been proved with absolute certainty, so that his
philosophical system would have an absolutely firm foundation upon
which to build a series of absolutely certain conclusions.
The reason I mention mathematics in that, in mathematics there are
things that may be true, but which cannot be treated as true until they
have been proved. Thus Descartes intends to say that a lot of stuff is
true, but he's not going to say that anything is true, until he is sure
that he has proved it. However, once he thinks that he has proved
something, he is going to then use that thing to prove other stuff.
Descartes had to start from the position that he knew nothing. He had
to take this position because, when he surveyed everything that other
people considered "knowledge," he found nothing that was not at least
speculative, and much that was absolutely unsupported. Descartes wanted
to build human knowledge on a foundation of absolute certainty, and he
found nothing in the existing structure of human belief that could
possibly be considered to have that level of certainty.
Descartes considered, and rejected the possibility of using our senses
as the foundation of knowledge. Human senses are inherently unreliable.
Not only do the senses provably make a lot of mistakes, we can never be
absolutely sure that we are not making some mistake that we don't know
about. Furthermore, humans often have very vivid and convincing dreams,
and there is no way to tell whether or not you are dreaming at any
given time. You could, for instance, be dreaming that you are reading
this essay right now.
Weirdly, Descartes doesn't even think that he can found a structure of
real knowledge in mathematics, even though mathematical calculations
might seem to give the kind of absolute certainty he seeks. His
reasoning seems to be that he cannot be certain of elementary
mathematical operations because his senses could be fooling him even
about such simple operations as adding five and seven. I find this idea
so weird that I don't even want to talk about it.
To make his ideas easier to understand to his readers, Descartes
creates a very important and powerful thought experiment. He creates
the idea of an "Evil Genius," or malevolent spirit who is capable of
deceiving him about absolutely any perception he might have. Descartes
is not saying that such a being exists. Rather he is offering us a way
to think about epistemological issues in a much more concrete fashion.
Consider again the idea of using our senses as a foundation for
knowledge. To most people, it seems clear that at least some of our
sensory experiences are absolutely certain. How could you doubt that
you are sitting in a chair right now? How could you doubt the existence
of the computer from which you get these words? But Descartes's point
is exactly that you can doubt those things, and the Evil Genius
hypothesis makes it clear that you can doubt them.
Do you have any way to prove that a malevolent spirit is not playing
with your senses right now? Do you have any way to prove that an Evil
Genius is not feeding you false sensory experiences? Can you prove that
an Evil Genius isn't making you imagine that you are sitting in a
chair, looking at a computer screen? If you cannot prove that your
present experiences are not being faked by a superpowerful deceiver,
then it is logically possible that those experiences really are fake.
And if it is logically possible that those experiences are fake, it is
logically possible that some or all of your present beliefs are false.
At this point, I want to remind you of Descartes's mathematical
approach. He is not saying that any of your beliefs are false. And he
is not saying that you will never be able to prove any of them true.
For Descartes, it is perfectly possible that most, perhaps even all of
your beliefs will turn out to be true. All he is saying is that nothing
has been proved yet. So, while it might turn out that the senses are
reliable after all, they cannot provide the absolutely certain starting
point he is looking for.
Descartes uses the idea of the Evil Genius to make his method of doubt
easier to understand. He asks, can we think of any statement that
cannot logically be false? That is, can we think of anything that we
could believe that the Evil Genius could not be fooling us about?
Imagine that you are trying to come up with a belief that cannot
logically be doubted. You take your belief in your own right hand, and
recognize that, if there was an evil genius, she could be supplying an
illusion of a right hand, so it is logically possible that you do not
actually have a right hand. And so on, for just about anything you can
think of.
Descartes's Argument
Descartes and then asks us to think about what would happen if you try
to apply this kind of reasoning to your own inner experience. Try to
doubt that you are doubting things. Try to doubt your own existence.
Or, try to doubt that you are trying to doubt your own existence. This
is getting weird, isn't it? Descartes thinks that this kind of
reasoning is not just bizarre, it's logically impossible. Could you be
doubting your own existence if you didn't exist? For Descartes,
something must exist to be doing the doubting. Specifically, for
Descartes, he must exist in order for him to be able to doubt his own
existence. Therefore, he concludes that it is not logically possible
for him to not exist, at least while he's doubting. In fact, for
Descartes, his own thoughts are conclusive evidence of his own
existence. That's why his slogan is "Cogito Ergo Sum," which basically
means "I think, therefore I exist."
Descartes now has the absolutely certain fact he was looking for, and
on this fact he attempts to build an entire philosophical system. This
argument goes step-by-step, like a mathematical proof, and when one
thing is proved, it then becomes available as a foundation for other
things. Let's follow along with Descartes's argument.
At this point in the argument exactly one thing is proved. Descartes
exists. He doesn't necessarily exist as a human body living in a
physical world. He might, at this point, exist as a disembodied mind
which also might be absolutely the only thing that exists at all. We
just don't know.
Descartes then also points out that the contents of his mind must exist
as well, at least as ideas in his mind. An object does not have to
exist in real life in order for it to exist as an idea in your mind.
For instance, consider the idea of five ton octopuppy. It weighs five
tons. It has big, puppy dog eyes, adorable floppy ears, and eight
massive fuzzy tentacles. And it attempts to destroy Cleveland, but is
distracted at the last minute by a huge stick thrown into Lake
Michigan. (Which is probably nowhere near Cleveland.) Okay, octopuppies
don't exist, but you do have the idea in your mind now, right? An idea
in your mind may not describe anything outside your mind, but it is
absolutely certain that it exists inside your mind. As an idea.
Descartes then asks where the ideas in his mind came from. Although, at
this point, it is possible that the world outside his mind does not
exist, it is also possible that it does exist, and that it is the
source of all Descartes's ideas. Descartes also considers another
possibility. He thinks that, whether the outside world exists or not,
it is also possible that at least some of his ideas are what is called
"innate." That is to say, they are ideas that existed in his mind
before he was exposed to the outside world. (You may remember this idea
from our discussion of Plato.) (You'd better!)
Descartes thinks that at least some of his ideas are innate. He reasons
that, if he can prove that his mind contains some idea that absolutely
could not have come from an external world, those ideas that could not
have come from the external world would have to be innate. He sees only
two possible sources for ideas. The external world, which may or may
not exist, and innateness. (Innatitude?) If it turns out that some idea
could not possibly have come from the external world, it absolutely has
to be innate. And that, of course, would prove the existence of innate
ideas.
As far as I can make out, Descartes thinks that at least three ideas
are innate. Those ideas are "sameness," "substance" and "perfection."
For each of these ideas he gives reasons why it has to be innate, and
then, from the last one, he goes on to make some rather startling
further conclusions.
The Wax Argument
Enter the wax. Descartes uses his example of the melting wax to
establish the existence of an innate idea. This would not just be an
important part of his overall system, but it would also kill the theory
of empiricism stone dead. Empiricism is the doctrine that absolutely
all knowledge can be derived from the senses. If Descartes can show the
existence of at least one idea that cannot be derived from the senses,
he will have shown that not all knowledge can be derived from the
senses, and that therefore empiricism is false.
The argument he uses is interesting. By which I mean that it is a bad
argument, but it is a little bit hard to say why it is bad. Because
this is a philosophy class, I'm going to try to explain his argument in
a way that makes it somewhat less than obvious how it is bad, which
will give you a chance to practice your critical reading skills, if you
want to. So as you read the following argument, think about each part
of it as you go, and try to figure out if it is logically good or not.
Some parts will be good, but at least one part will be bad. See if you
can figure out which one it is.
First, let me tell you something about logic. Sometimes you are allowed
to make assumptions, and other times you are not. What you are allowed
to assume depends on what you are trying to prove. For instance, if you
were trying to prove that monkeys can fly, you would not be logically
allowed to start out by assuming that they have wings. However, if you
are trying to prove that monkeys cannot fly, you can start out by
assuming they have wings, or even that they can fly! You can start out
by making these assumptions because they logically contradict the point
you will eventually make. If assuming that monkeys can fly inevitably
leads to the conclusion that they cannot, then it is logically okay to
start out by assuming they can. Similarly, if Descartes was trying to
prove that the senses can be the source of knowledge, he cannot start
out by assuming that the senses are reliable. But if Descartes is
trying to prove that there are ideas that the senses cannot be the
source of a certain idea, then it is perfectly okay for him to begin by
assuming that the senses are reliable.
Descartes starts with a piece of honeycomb. This is a piece of beeswax
organized into hexagonal cells. It is yellow, hard, rigid, waxy, tastes
of honey, and smells of bee......... stuff. He has this wax in a room
that is heated by a fire in the fireplace on the other side of the
room. The wax starts out in the coldest part of the room. In this part
of the room, is cold, hard, rigid, tasty and smelly.Now suppose that
Descartes puts the wax down on a table next to several other items,
such as an inkwell, a book, a matchlock pistol, and a statue of
Charlemagne made entirely of cheese. Descartes then goes into another
room for some wine, and while he is gone, the chambermaid comes in and
rearranges the table so that the inkwell ends up where the wax was in
the wax ends up where the book was, and so on. When Descartes comes
back into the room, how does he tell which of the objects on the table
is his wax? Well, he uses his eyes to look for something yellow with a
pattern of repeating hexagons. He uses his fingers to see if this thing
is hard, rigid and waxy feeling. He uses his nose to..... well, you get
the picture. Descartes uses his senses to tell him that this is the
same object that he left on this table with the other items. At this
point, Descartes's sensors are capable of telling him that it is the
same piece of wax.
Descartes then moves the wax progressively closer and closer to the
fire. As the wax gets closer to the fire, its sensible properties begin
to change. It begins to get soft. It begins to get malleable. It starts
to lose its shape. It loses its smell. It stops tasting of honey. It
loses its color. Finally, it is nothing but a puddle of clear liquid on
the hearth. Now, imagine that Descartes asks you whether or not you can
use your senses to tell whether or not this is the same thing that it
was at the start of this process. If you say you can, he asks you what
piece of sensory information tells you this is the same object? It
can't be the shape, because the shape here is different. It can't be
the hardness, because the object is no longer hard. It can't be the
rigidity, because this object is hardly rigid. It can't be the color,
because the color's not the same, and so on. Descartes says that your
sensory experience of this object cannot possibly be what is telling
you that it is the same object that was once hard, rigid and yellow.
Descartes then points out that there are only two possible sources for
any idea. The idea can be innate, or it can come from the senses. The
idea that this is the same wax cannot come from the senses, so it must
be innate. Even if we assume that the senses are reliable, it turns out
that there is something that we know that the senses cannot possibly
tell us. The only other possible source for this knowledge is that it
is innate, so that must be where the idea comes from. If at least one
idea is innate, then it is not true that absolutely all knowledge can
be derived from the senses. If it is not true that all knowledge can be
derived from the senses, then empiricism is false.
Now, can you see anything wrong with this reasoning?
Substance.
The idea of "substance" is an interesting one in many ways. First, it
is interesting how the usage of this word has changed over the years.
Nowadays, "substance" is taken to mean "stuff," as in "I have this
strange substance on the bottom of my shoe" or "take a look at this
weird substance." When the word "substance" was coined, it was not
something you could find on the bottom of your shoe, or even take a
look at at all. "Substance" meant "that which stands under," and it
referred to something that could not be seen, or touched, or tasted, or
even experienced in any way whatsoever. Substance was the unperceivable
thing that held together all of the properties of an object.
And that is the second interesting thing about substance. Philosophers
in Descartes's time and before often believed in the existence of
unperceivable things. Substance was the most important of these things.
Just about every philosopher Aristotle to Descartes believed in
substance. They believed in substance because they thought it was
impossible to explain the existence of objects without the existence of
substance.
The argument for substance goes something like this. Say you pick up a
coffee cup and ask what it is that makes this coffee cup the thing that
it is. is it the color? No, because you could take away that color, and
it would still be the same coffee cup. Is it the weight? No, because it
could have a different weight, and still be the same coffee cup. Is it
the shape? No, because changing the shape wouldn't make it a different
thing. And so on through all the sensible properties of the cup.
Aristotle reasoned that there must be something that made the coffee
cup the thing that it is. He reasoned that it could not be any of its
sensible properties, because any of those could be changed without
making it a different object. Since it wasn't anything that could be
sensed, it must be something that could not be sensed, and he named
this intangible thing "substance."
For Descartes, the concept of substance provided another example of an
innate idea. His argument was as follows. We know that substance
exists, because objects could not be the objects that they were without
it. But substance is absolutely intangible. We cannot sense it in any
way. So our knowledge of substance must come from some source other
than the senses. The only other way we could have the idea of substance
is that it is innate, so "substance" is another example of an innate
idea, and is therefore another independent argument that empiricism is
false.
Now, can you see anything wrong with this reasoning?
Solipsism.
It is worth taking a moment here to think about what Descartes has
proved at this point. (If he has proved ) Descartes thinks that he has
proved, for certain, that he exists, at least as a mind, that his mind
is furnished with ideas, and that at least some of these ideas are
innate. That's it. At this point in the reasoning process, the only
actual existence that Descartes has proved is his own. This means that
it is still logically possible that the only thing that exists is
Descartes himself. If Descartes stopped at this point, and asserted
that he was in fact the only thing that existed, he would be asserting
the doctrine of "solipsism." This is the doctrine that only you exist.
Every individual solipsist asserts a slightly different doctrine. If
Jack is a solipsist, Jack holds that only Jack exists. But if Jill is a
solipsist, Jill is asserting that only she exists, which means that she
is also asserting that Jack doesn't exist. Solipsism is thus
interesting in that people who hold the doctrine must necessarily
disagree with each other. If you are a solipsist, you will think that
you exist, and I don't. Whereas, if I am a solipsist, I will think that
I exist, and you don't.
Solipsism might be thought of as a dilemma for Descartes. We might
assume that Descartes does not want to solipsism to be true. Descartes
wants to prove that a world exists external to himself, and so he has
to figure out a way to prove this with the same certainty that he has
proved his own existence.
Perfection.
The "concept of perfection" argument is Descartes's answer to
solipsism. He begins by pointing out, quite correctly, that his mind
contains this concept of perfection. Then he asks where this idea could
possibly have come from. He says that it could not possibly have come
from the senses because there is nothing in the world that is perfect.
His reasoning is that if the senses supplied us with an idea, they
would do so by having a sensory experience of a thing that had that
property. If the senses supplied us with the idea of "green," they
would do so by having an experience of a green thing. If the senses
supplied us with the idea of "square," they would do so by having a
sensory experience of a square thing. And if the senses supplied us
with the idea of "perfection," they would do so by having an experience
of a perfect thing. But if you look very carefully at the world, you
will see the world does not actually contain any perfect things. So,
the concept of perfection cannot come from the senses, and so it must
be innate.
Descartes then takes his argument a step further than he did for
sameness and substance. He asks how the idea of perfection could ever
have become innate in his mind. His rule of logic is that ideas can
only come to be innate in a mind by contact with things they are ideas
of. By this rule, the mind can only have an innate idea of "green" by
contact with a green thing. So Descartes reasons that his mind must at
one time have had contact with a perfect thing, and since you can't
have actual contact with things that didn't exist, a perfect thing must
exist.
Descartes reasons that this perfect thing cannot be himself, for the
simple reason that he is not perfect. I personally find it a little bit
disturbing that Descartes thinks himself imperfect because he doubts.
For Descartes, a perfect person would have no doubts whatsoever. When
you consider that all of the greatest evils of history, such as the
Holocaust and the Armenian genocide, were committed by people who had
absolutely no doubts whatsoever, I find it hard to believe that the
possession of the ability to doubt should be counted as an
imperfection. Still, Descartes isn't perfect, so the concept of
perfection did not come from himself, and he cannot be this perfect
being.
In fact, Descartes believes that there is exactly one possible source
of the concept of perfection. He believes that there is exactly one
possible perfect being. This would be a being that is perfectly
powerful, perfectly knowing, and perfectly good. At this point,
Descartes defines this perfect being purely in terms of reasoning about
what a perfect being would be like. A perfect being would not have any
weaknesses, a perfect being would not have any blind spots, a perfect
being would not have any meanness or cruelty, and so on. In fact,
Descartes defines a perfect being as one that lacks anything they could
logically be considered an imperfection. And, because Descartes has the
concept of perfection, this perfect being necessarily exists.
Descartes decides to call this perfect being "God." Or, to put it
another way, he claims that this argument proves that God exists. This
is important in terms of Descartes's overall project of proving the
compatibility of philosophy and religion. If philosophy, properly
understood, logically proves the existence of God, then nothing else
that is genuinely proved by philosophy will ever contradict the
existence of God. For Descartes, this is all he really needs to show
the compatibility of philosophy and religion.
Thus Descartes believes that he has escaped solipsism. He has not only
proved his own existence, he has proved the existence of one other
being, namely God. And, he thinks, he has proved the existence of God
with absolute certainty.
Now, can you see anything wrong with this reasoning?
The Reliability of the Senses.
At this point in the argument, Descartes has only proved the existence
of two objects, himself and God. But once he has proven the existence
of God, he can use this to prove other things. His argument is
interesting because it is rooted in the definition of God he was
logically compelled to use in the previous stage of his argument. If
God was not defined as an absolutely perfect being, the previous stage
of his argument could not work at all. And it is from the same
definition of God as an absolutely perfect being that he draws all the
rest of his conclusions.
The first thing he does is to use his definition of God to prove that
there is no Evil Genius. This is based on the fact that a perfectly
omnipotent, omniscient, and beneficent being would not allow such a
deceptive being as the Evil Genius to have free reign over human
beings. A perfect being would not allow such deceptiveness. Think about
it, suppose you have two acquaintances, one of whom is always deceiving
you, and the other is knowingly letting it happen. Would you consider
the second person to be a perfect being? I certainly wouldn't. So there
is no Evil Genius, and no being actively trying to systematically
deceive us.
Next, Descartes asks if a perfectly good being would allow us to have
senses that could be systematically wrong about everything? Well that
would be a cruel trick, wouldn't it? A perfectly beneficent being would
not allow us to be systematically wrong about everything, so we don't
have the kinds of senses that can be systematically wrong. In fact, we
must have the kind of senses that, if used properly and carefully, can
eventually give us accurate information. It god allowed us to have
senses that could not generate accurate information, then God would not
be perfectly benevolent.
So, from the certainty of his own existence and the concept of
perfection in his own mind, Descartes deduces the existence of God and
the ultimate reliability of the senses.
Now, can you see anything wrong with this reasoning?
The Existence of the World.
If our senses are ultimately reliable, then it follows that those
things that we are most certain of must actually be true. The things we
are most certain of our of course the things for which we have most
evidence, and the things that are most reliably observed when we are
most careful to observe correctly. Chief among these things is the
world outside of our own heads. If it turned out to the world outside
our own heads did not exist, that would prove that our senses were
profoundly unreliable, which in turn would prove that the perfect being
did not exist, which in turn would prove that Descartes's mind does not
contain the concept of perfection. But it is absolutely certain that
Descartes's mind contains the concept of perfection, and so it is
absolutely certain that the perfect being exists, and so it is
absolutely certain that our senses are not profoundly unreliable, and
so it is absolutely certain that the external world exists.
There is a subtle but profound difference between Descartes's
rationalism and empiricism. Empiricism starts by assuming that the
senses can give us knowledge. Empiricism does not try to prove
absolutely that the senses are reliable. Instead, it tries to prove
that the senses are the only possible source of knowledge, and goes
from there. This means that, in empiricism, every piece of knowledge
gotten from the senses is at least a little bit uncertain. Nothing is
absolutely certain in empiricism, not even that which is supported by
the very best evidence of the senses. The situation is different in
Descartes's rationalism. If Descartes's argument for the reliability of
the senses is correct, then at least some sensory information is
absolutely reliable. This means that, for Descartes, at least some
sense-based knowledge is absolutely certain. So, weirdly, the system in
which knowledge is not ultimately based on the senses is also the only
system that says that sense-based knowledge can be absolutely certain.
Weird.
So there you have it. Descartes thinks that he has given a series of
proofs that is as logically rigorous as a series of proofs in
mathematics. As he sees it, he proves his own existence and from that
he proves the existence of innate ideas. He proves that the concept of
perfection has to be innate, and from that proves that god exists. From
the existence of god, he proves the reliability of the senses. And
finally, from the reliability of the senses, he proves the existence of
the external world. Impressive, huh?
A Moment of Reflection.
At this point, I would like to invite you to take the time to go over
your notes on this reading and everything else you have read so far for
this module. Look carefully at Descartes's reasoning and try to figure
out which parts of his reasoning are logically solid, and which parts
might have problems. You don't necessarily have to find all of
Descartes's mistakes. Lots of people had no idea that Descartes had
made any mistakes at all. Lots of prominent philosophers thought that
his reasoning was perfectly fine. Still, it is very important to have
practice in attempting to figure out where chains of reasoning go
wrong, and so I think it is important for you to take at least a few
minutes to think over Descartes's logic.
Ideally, you would do this over a period of days. You would work over
Descartes's logic thoughtfully in your own mind, and make new notes of
new ideas as you thought of them. You would let these issues sit in the
back of your mind as you had a cup of coffee, or drove to work, or
wrestled an alligator, so that new ideas and insights could rise
naturally to the surface.
But you probably don't have time for that. So just struggle with
Descartes's reasoning as best you can in the time you have before you
go on to see what I have to say about problems with Descartes's
reasoning.
Problems with Descartes's Reasoning.
The most solid part of Descartes's argument is his "cogito ergo sum,"
but even that may have a subtle problem. Imagine that you are in a dark
room by a floor that has a hole in it leading to another dark room. You
cannot see anything, but you can put your hand through the hole to feel
what is there. You do so, and you find your fingers get very wet. From
this, you infer that there is water in the other room. Should you also
logically infer that there is a bucket, or other container, holding the
water? Before you say "of course," I want to point out that it is
possible that you are in the international space station and that the
water on the other side of the "floor" is in fact a large globule of
water floating freely in zero gravity. In that case, there would be no
bucket. So the fact that all you feel is water, and you neither see nor
feel any container, means that you cannot logically infer that there is
a bucket or any other container on the other side of the floor. Now
think about what Descartes can logically infer from the existence of
his own doubts and other ideas. Certainly, he can infer that a
collection of thoughts exists, and he could reasonably call this a
"mind." But can he infer anything beyond this? Can he infer the
existence of a separate, independently existing thing that is not
itself a thought, or collection of thoughts, but which contains
Descartes's thoughts and keeps them together? I'll leave you to worry
about this, because we're not going to deal with it this module. We
will take this issue up later, when we deal with the work of David Hume.
The wax argument purports to prove that the idea of "sameness" has to
be innate. It tries to do this by showing that the senses cannot convey
this idea. The argument relies on two claims. First, there is the claim
that we know it is the same wax. Second, there is the claim that we
could not have gotten this knowledge through the senses. But the claims
cannot both be true. If our senses do not tell us that it is the same
wax, how do we know? Remember when I asked you to imagine that
Descartes identified his piece of wax after being out of the room for a
few minutes? Did he really know that it was the same wax? It is in fact
logically possible that the chambermaid broke his piece of wax and
hurriedly replaced it with another piece of wax that she happened to
have. Suppose also that Descartes had been distracted during his
demonstration of moving the wax from one side of the room to the other,
and the chambermaid had made the switch while he wasn't looking.
Descartes would then believe that the puddle of liquid at the end of
the process was in fact the same object that he had started with, but
he would be wrong. The only circumstances in which Descartes could
actually be certain that it was the same wax would be if he was paying
careful attention the whole time, never allowed himself to be
distracted: and followed the piece of wax through the entire process.
But this means that the anyway Descartes could be certain that it was
the same wax would be if he was paying attention to sensory information
the whole time. And that means that the way he knows it is the same wax
it is from sensory information. Yes, the puddle of liquid at the end of
the process has no sensory features in common with the reading yellow
honeycomb at the beginning, but as he watches the wax on its journey,
Descartes can see that the object that was rigid a moment ago is just
now a little softer, and that is certainly a piece of sensory
information. In point of fact, the only way we ever know that an object
is the same object that we saw before is from careful analysis of
sensory data. So Descartes is simply wrong that he both knows that it
is the same wax, and that information could not have come from sense
data because the only way he could know it is the same wax, is if
precisely that information does come from sense data.
Imagine that Descartes is trying to demonstrate that substance exists
and that our knowledge of its existence is not based on sense data.
Suppose he starts by telling you that you already have the idea of
"substance" in your mind. You deny this, and say that you had
absolutely no conception of the idea before he mentioned it, and in
fact found it a very weird idea that took a lot of getting used to. He
claims that he can prove that you already have the idea of substance in
your mind. You tell him, that he has to do it without referring to
sense data. He says, "okay, look at this cup." You reply "you mean,
consider the sense data we're currently getting of a cup-shaped patch
of color, and so on?" At this point, Descartes finds that he cannot
explain the idea of substance without referring to sense data. So then
he tries a different tack. He asked you if you have the idea of
existence. You reply that you have the idea of things that can be seen,
touched and so on, and the word "existence" refers to things of this
kind. He replies that it is impossible for things to exist as visible,
touchable entities if there is not also an unseeable, untouchable thing
holding all of those tangible properties together. You can then reply,
that if that really is a logical rule, then the belief that substance
exists is founded completely on sense data, and therefore, if we know
substance exists, we do so by applying logic to sense data. This means
that we can explain the existence of the concept of substance in our
minds without having to think that the idea is innate. (And if it isn't
really a logical rule, we have no reason to think that substance exists
at all.)
Descartes believes the concept of perfection cannot come from the
senses, but he is wrong. Descartes believes correctly that there are no
perfect objects found in nature. Things that appear to be perfect
always turn out on closer examination to have small but real
imperfections. Still, there are two ways that the concept of perfection
can come from our senses. First, we can make mistakes. We can see
something that appears to us to have no flaws, and from that get the
idea that a perfect thing exists. Even if we lay to examine the object
and find it to have flaws, we got the idea of perfection by seeing it
without noticing any of the flaws. Second, we can use our imaginations.
We can examine any object and imagine how it would be if it had no
flaws. From this imaginative exercise, we can develop the concept of
perfection. Thus, we do not need to have actual contact with an
actually perfect thing to have the concept of perfection. Thinking
about imperfect things will do just fine.
As far as I can tell, these are the only serious flaws in Descartes's
reasoning. Still, they are quite enough to knock down his arguments for
innate ideas and the existence of god. And, ultimately, these kinds of
mistakes and problems also knock down rationalism. This does not mean
that Descartes's work was worthless. Quite to the contrary, he did not
succeed in setting philosophy of an absolutely certain foundation, but
his failure to set philosophy on the same kind of foundation as
mathematics taught us an awful lot about reasoning. Philosophy can be
done rigorously, but it cannot be done the way Descartes tried to do
it. And I think this is one of Descartes's most important contributions
to philosophy. He was an absolute genius, and so if he could not make
rationalism work, nobody could.
Poor Quality Videos of My Lectures About
Descartes
Rationalism and the
quest for certainty
The method of doubt
The Wax, The God,
and the External World
Descartes Rising 1
Descartes Rising 2
Potential Exam Questions
Practice answering these exam questions after you have worked though
all the readings and both quizzes.
The following questions are very much like the questions that will
appear on the next exam. If you practice answering them without your
notes, and then check your answers against your notes, you will be much
better prepared for the exam.
Your answer should demonstrate that you understand all
the logical relationships between all the
relevant facts for that particular
question. The deeper the understanding
you demonstrate, the better your grade will be.
Many of the topics in this class involve doctrines that are mistakenly
supported or, more interestingly, mistakenly criticized by others.
Understanding is best demonstrated by something like the following:
Explaining a doctrine clearly and completely, including all relevant
details and nuances.
Explaining at least one criticism of that doctrine clearly and
completely.
Explaining clearly and completely why
that criticism fails. (This will usually involve showing that the
critic has made some unfounded logical assumption, has mischaracterized
or misunderstood the doctrine he is criticising, or has made some other
logical or factual mistake.)
It is pointing out people's real logical mistakes that does the most to
demonstrate your understanding of an issue, so do your best to follow
the logic of these issues all the way out to the end.
If you're not sure how to address an exam question, at least try to
fully explain and properly organize all the information relevant to the
question. This will include a variety of ideas developed in response to
the above questions in your personal reading and in class discussions.
I have added some hint questions to indicate the kind of things you
should think about for your answer. The hint questions
will not appear on the exam.
The Sample Questions
Explain Descartes's philosophical method and his
justification for that method.
Why can't Descartes start by building on the structure of knowledge
that existed before him? Does Descartes think that there are some
things which are so obviously true that we don't need to worry about
them? Explain. What must Descartes do before he can even begin to
produce real knowledge? Explain your answers, giving Descartes's
arguments where appropriate.
Explain Descartes's arguments why neither the senses nor
mathematics can be the foundation of knowledge.
What is Descartes's basic philosophical method? What standard must
something meet in order for Descartes to accept it as a fit foundation
for knowledge? Why can't the commonsense picture of the world based on
the senses meet this standard? What kind of knowledge is mathematics?
Why is it the kind it is? Does the truth or falsity of mathematical
statements depend on the existence of a particular kind of world?
Explain. How are mathematical truths determined? Do mathematical facts
have the same kind of built-in uncertainty that observational facts do?
Explain. Given all that, how come Descartes still can't use mathematics
as his foundation?
Explain and Critique Descartes's famous "Cogito ergo
sum" argument.
What imaginary being does Descartes postulate in order to begin this
argument? Why does he postulate this being? What kinds of beliefs are
undermined by postulating this being? What exactly is proved by
Descartes argument? Would you prove the same thing if you used the same
argument? Explain in detail how Descartes proves what he thinks he
proves. Now explain your instructor's critique of this argument. What
do I think Descartes thinks he proves exactly?
What do I think Descartes actually proves? What
is the difference? Why is this difference a problem for Descartes?
Explain and Critique how Descartes uses wax to try
to establish the existence of an innate idea.
What is an innate idea? What other kinds of ideas are there? How are
innate ideas different from the other kind? What innate idea is
generated by the wax example? Why is this supposed to be an
innate
idea rather than an idea of the other kind? Now explain your
instructor's critique of this argument. What do I think is wrong
with Descartes argument here? What do possibilitie do I think Descartes
ignores how is this fatal to his argument?
Explain and Critique Descartes's argument for the existence of God.
What is the basis for Descartes' argument for the existance of God?
What are the two possible sources for this thing? What other
explanations for this thing does Descartes rule out, and what
explanation does Descartes think is left? How is this explantion
related to Descartes' definition of God, and how is all this supposed
to prove that God exists? What is the major flaw in Descartes'
reasoning, and how does this flaw cause Descartes' argument to fail?
Explain and Critique Descartes's argument
against the existence of the evil genius.
What
claim does Descartes start with, and by what chain of reasoning does
Descartes' think he has come to disprove the existence of the evil
genius? What is the major flaw(s) in Descartes reasoning, and how does
this flaw bring about the failure of Descartes' argument?
Explain and Critique Descartes's argument for the existence of the
physical world.
Beginning with the existence of God and the nonexistance of the evil
genius, trace out the chain of reasoning that Descartes uses to prove
the existance of the external world. In Descartes's view, after this
argument, is it possible that there really is in fact no external world
at all? Why or why not? Why is the definition of God important here?
Why is Descartes' view of knowledge important
here? What flaw(s) if any can be found in this argument, and if it is
flawed, found, how does the argument fail?
See you in class.