Descartes
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.
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.
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 from 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
Helpful Questions
After reading the above, you should be able to answer the following questions.
What did the majority of churchmen believe about dissenting views of reality?
What belief was the biggest support for the church's view of reality?
How did this belief seem to logically support the idea of the existence of God?
How did Galileo upset this applecart?
Why is it important that Galileo did not try to save the appearances?
What was the problem for Descartes' project of writing an astronomy text?
How did Descartes try to solve this problem?
What did Descartes find when he turned his rigorous mind to philosophy?
What did Descartes set out to do?
How was Descartes' method like mathematics?
What does "deduce" mean?
What is the first interesting thing about plane geometry?
What is the second interesting thing about plane geometry?
How was Descartes' method different from mathematics?
Under what circumstances will Descartes say that something is true?
What position did Descartes start from?
Why did he start from that position?
Why didn't Descartes start with the existing structure of human knowledge?
Why didn't Descartes use the senses as the foundation of knowledge?
Why didn't Descartes use mathematics as the foundation of knowledge?
What is the "evil genius?"
Is there any practical limit to the evil genius's power of deception?
Is Descartes saying that all your beliefs are false?
Is Descartes saying that your beliefs will never be proved true?
What is Descartes saying?
What happens if you try to doubt that you are doubting things?
Can the evil genius cause Descartes to have deceptive thoughts if Descartes doesn't exist?
What is meant by "Cogito Ergo Sum?"
Why is this "Cogito Ergo Sum" important to Descartes?
What exactly does Descartes know at this point?
How do ideas (like the octopuppy) exist?
What question does Descartes ask about the ideas in his mind?
What two possibilities does Descartes consider?
What is an "innate" idea?
Why does Descartes think he can prove that some of his ideas are innate?
What is empiricism?
What happens to empiricism if Descartes proves that even one innate idea exists?
What is the piece of wax like when Descartes starts talking about it?
What happens to the piece of wax as it gets closer to the fire?
What is the wax like when Descartes is finished with it?
Does the wax have any sensory characteristics that are the same all the time?
Why does Descartes think that the ideas of "sameness" and "substance" are innate?
Why does Descartes think that the wax proves that some ideas are innate?
Why does Descartes think that the wax proves that empiricism is false?
What is meant by the word "substance?"
What is the argument for substance?
Why does the idea of substance have to be an innate idea?
What is "solipsism?"
Why is solipsism a problem for Descartes?
Why does Descartes think the concept of perfection cannot have come from the senses?
According to Descartes, what is the only way an idea can come to be innate in his mind?
Why does Descartes think that a perfect thing must exist?
Why can't the perfect thing be Descartes himself?
Why does Descartes think that he himself is not perfect?
What does Descartes think is the one possible source of the concept of perfection?
Why does Descartes think he has proved the compatibility of philosophy and religion?
Why does Descartes think he has disproved solipsism?
What else does Descartes think he has proved?
Does he think he has proved this thing with high probability, or with absolute certainty?
For Descartes, what does the perfection of God prove about the evil genius?
How does it prove this?
For Descartes, what does the perfection of God prove about the reliability of the senses?
How does it prove this?
For Descartes, what does the perfection of God prove about the existence of the world?
How does it prove this?
Overall, what does Descartes think he has proved?
The questions on this page are intended to help you work out a critical evaluation of the claims given in the text.. Write out the answers in your own notes. You don't turn any of these in either. You should answer these questions after you have done the reading questions. Answer these as well as you can based on your understanding of the assigned reading, and your own independent critical thinking.
At this point, your notes should lay out a more-or-less detailed elaboration of the following argument structure.
Descartes thinks:
Only that which is known for certain can count as knowledge, only things that can not be rationally doubted can count as knowledge,
There is always at least a shadow of doubt about the senses, so the senses cannot provide a basis for knowledge.
And, since a shadow of doubt exists even for mathematics, so mathematics cannot provide a basis for knowledge.
But, because he cannot rationally doubt his own existance, he must exist as a thinking thing.
And, since he senses his own ideas, those ideas exist in his mind.
In the "wax story," he says that the puddle of liquid is the same thing as the chunk of honeycomb he held in his hands a few minutes ago.
The knowledge that they're the came could not have come for the senses.
Because he has this knowledge that could not have come from the senses, that idea at least must be innate, so innate ideas exist.
The concept of "perfection" could not have come from Descartes himself, because he himself is not perfect.
Because the concept of "perfection" must have come from a perfect thing, that perfect thing must exist.
God is the only perfect thing, so the fact that a perfect thing exists means that god exists.
God, a perfect being, cannot allow deceit, so god's existance means that the Evil Genius cannot exist.
Since the Evil Genius cannot exist, our senses (and mathematics) must be reliable after all.
Since our senses are reliable after all, those things they tell us clearly and unequivocally must be true.
Since our senses tell us the external world exists, and they're reliable, the external world must exist after all.
Now, you're not going to have to understand all of the above chain of reasoning, but you are going to have to understand some of it very deeply, which means you're going to have to spend some time thinking about possible logicalproblems with various points in this argument.
The other thing I want you to understand is that, as you go down the list, each later point depends absolutely on all the points before it, so if, say, point 8 fails, all the points (9-15) after it collapse, and Descartes argument then fails to achieve it's overall goal. Seldom has there been such potential for such a small wound to prove so fatal.
For each of the steps in Descartes' argument, there are various questions we can ask about it's logical strength.
You're not supposed to deeply understand all of this. But you are supposed to spend a reasonable amount of time doing your best to understand as much of this as you can
1. Only that which is known for certain can count as knowledge,
only things that can not be rationally doubted can count as
knowledge,
Do we really need a standard of
knowledge that is quite this strict?
What
kind of standard would you think appropriate?
If
it turns out that we can do with a standard that is not as strict as
Descartes wants, what does that do to Descartes' argument?
2. There is always at least a shadow of doubt about the senses, so
the senses cannot provide a basis for knowledge.
Is
there anything you know through the senses that you think cannot be
rationally doubted?
3. And, since a shadow of doubt exists even for mathematics, so
mathematics cannot provide a basis for knowledge.
In
your opinion, is mathematics something we know through the
senses?
Or is mathematics something we can
only work out in terms of pure logic?
Is
"two plus two equals four" something we know to be true
because we go out and physically add things to other things?
Or
is it something we know because we can sit down and work it out
without ever looking out into the world?
4. But, because he cannot rationally doubt his own existance, he
must exist as a thinking thing.
Descartes
might have proved that his thinking exists, but has he proved that
any separate thing exists apart from the thinking itself?
Imagine that your neighbor's house has a perfectly green composed of nothing but grass. Now imagine that you come by one day, and you see a daisy in one corner of the lawn. The next day, there are two daisies. The day after that, there are more daisies trailing away towards the center of the lawn. Finally, there is a meandering string of daisies leading from one corner of the lawn to the other. Let us take this experience as proving that there are daisies in the lawn. If we do so, does it also prove that there is a separate, non-daisy, daisy planting thing?
If the existence of daisies in the lawn cannot prove the existence of a separate, otherwise undetectable, daisy planting thing, can the existence of thoughts prove the existence of a separate thought-making thing?
Consider also a flock of pigeons. When you see a flock of pigeons wheeling through the air, it is pretty clear that the flock exists. But does it exist separately from the pigeons? If the pigeons all dispersed to separate individual locations, would that flock still exist?
Based on this reasoning, what is a mind?
5. And, since he senses his own ideas, those ideas exist in his
mind.
But do they exist like fish in a
barrel, or like pigeons in a flock?
6. In the "wax story," he says that the puddle of liquid
is the same thing as the chunk of honeycomb he held in his hands a
few minutes ago.
Remember that at this
point in the argument, Descartes has not ruled out the existence of
the Evil Genius.
Has Descartes given us
any reason to think that it is impossible for the Evil Genius to have
fooled him into thinking that they are the same thing?
Has
he given us any reason to think it is impossible for the Evil Genius
to have fooled him about all the various transformations of the
wax?
Is there any reason to think that the
Evil Genius has not fooled him about the very existence of the
wax?
If Descartes cannot absolutely rely
on his senses, and he demands certainty, what happens to his argument
here?
But, is Descartes trying to prove
that the honeycomb and the puddle are the same thing, or is he just
asking us to imagine that they are the same thing?
Is
he trying to prove that sensory information is reliable, or is he
trying to prove that even if sensory information is reliable, there
are still some things that absolutely cannot come from the senses?
7. The knowledge that they're the same could not have come for the
senses.
Are we absolutely sure that
knowledge of sameness doesn't come from the senses?
In
the story, where does Descartes get the idea that the honeycomb and
the puddle actually are the same?
Does he
just assumed that that the same, or is this belief based on
something?
If he just assumes that they're
the same, what does that say about his argument?
Can
you really prove anything based on an argument that is itself based
on an assumption?
Imagine I try to prove that magical beings exist. My argument is as follows. "Dragons exist, dragons are magical beings so, since dragons exist, magical beings must exist!" If my first premise is an assumption, have it proved anything?
If Descartes's belief that they're the same thing is based on something, what could it be based on?
What are our ideas of sameness normally based on?
Suppose that while Descartes is demonstrating his wax example, you have to leave the room. Suppose that while you are out of the room, someone else brings in a honeycomb and does the same things as Descartes to it. When you come back, you see two exactly similar puddles of wax. Without talking to people who were in the room, can you tell which is which? If you do ask people who were in the room, how do they know which one is the same as Descartes's original honeycomb? Suppose Descartes was distracted, and put his wax down for a second. Suppose that, unknown to Descartes, someone substituted a different piece of wax, and Descartes went on with his demonstration all unknowing. Afterwards, he asserts with complete confidence that the puddle of wax before him is the same wax as the honeycomb he started with, even though everyone else knows it isn't. Or would he know it isn't the same wax? How would he know? How do we justify claims of sameness and difference in ordinary life? How do we learn the concepts "sameness" and "difference" in ordinary life? Is it really impossible to have gotten these ideas from sensory information?
8. Because he has this knowledge that could not have come from the senses, that idea at least must be innate, so innate ideas exist.
Well, let's think about that.
How do you know that two things are the same, anyway?
Do you ever really know, with absolute certainty, that two things are the same?
Has Descartes proved that it is ever the case that we can be absolutely certain that the evil genius has not made substitutions?
Has Descartes given us any reason to think that this supposedly innate idea is not actually an innate mistake?
Has Descartes given us any reason to think that this supposedly innate idea was not actually added to our minds by the Evil Genius?
9. The concept of "perfection" could not have come from Descartes himself, because he himself is not perfect.
Why does the concept of "perfection" have to come from a perfect thing?
Is it really true that a concept that can only come from an object that has the property described by the concept?
Do we have any reason to think that we cannot get concepts from things that don't have the property described a concept?
Where does this rule that the concept must come from a thing that has the property that come from?
Is it a valid logical principle, or does it seem to be just something that Descartes made up?
Doesn't Descartes' mind also contain the concept of "sameness?"
Does god have the property of being the same as something else?
Does Descartes have the property of being the same as something else?
Can you think of a way that god could have the property of sameness?
But does a supposedly changeless god have the property of existing in different forms at different times?
1. Because the concept of "perfection" must have come from a perfect thing, that perfect thing must exist.
Do you see anything wrong with this bit of logic? (I don't, actually)
Could anything come from something that doesn't exist?
11. God is the only perfect thing, so the fact that a perfect thing exists means that god exists.
Suppose we assume that Descartes' argument works all the way up to argument 10, where he "proves" that a perfect thing exists.
Suppose we give the name "Perfecto" to the perfect thing whose existence Descartes has proved.
Has Descartes given us any reason to believe that Perfecto must be the god he believes in?
Has Descartes given us any reason to believe that Perfecto is not Brahman or Apollo?
12. God, a perfect being, cannot allow deceit, so god's existance means that the Evil Genius cannot exist.
13. Since the Evil Genius cannot exist, our senses (and mathematics) must be reliable after all.
14. Since our senses are reliable after all, those things they tell us clearly and unequivocally must be true.
15. Since our senses tell us the external world exists, and they're reliable, the external world must exist after all.
To be honest, I can't see anything wrong with the last four steps here. Still, if even one of the previous steps is bad, the whole thing falls apart.
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
8. 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.
9. 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?
10. 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?
11. 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 ignoreshow
is this fatal to his argument?
12.
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?
13.
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?
14.
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?
Any exam answer can be enhanced by addition of any comments that occur to you. The more you think about a topic, the more likely you are to come up with something that can earn you a little more credit for your answer. I never deduct points, so it can't hurt to add your own thoughts.
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