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8 Descartes, Meditations I the demonstrations are so
certain that even if our experience seemed to show the opposite, we should
still be obliged to have more faith in our reason than in our senses. – Descartes, Principles of philosophy, Part II,
Article 52
This quest for
foundational principles is one of the characteristic features of Descartes’s philosophy.
Other philosophers have been willing to settle for less — for
probability or for provisional suppositions that, while not certainly true,
can be confirmed by sensory experience.
However, Descartes’s conception of the
proper method for gaining knowledge left him with no choice but to make
stronger demands. The first rule of
his method dictates that we start with axioms, and the third rule stipulates
that all knowledge is to be obtained by deduction from these axioms. Because he was confident of the truth of
the mechanist natural philosophy, which postulates that the real world looks
very different from the coloured, scented, warm and cool bodies we experience
through our senses, Descartes expected that when he proceeded in accord with
his method, his deductions from axioms would establish the existence of
things that are very different from what we see around us. So, for Descartes, the fact that deductions
from axioms might come into conflict with everyday experience or with common
sense would not by itself be a reason to think that
the axioms are wrong. Since he could
not hope to verify his principles after the fact, by reference to their
consequences, he had to be absolutely certain, at the outset,
that he could rely on them. He
accordingly adopted the most rigorous criterion possible for identifying and
admitting first principles: if he could even imagine a claim being false
(even by the wildest possible speculation), he would not admit it as a first
principle of his philosophy. This is what we can
call Descartes’s first criterion of truth (his
first criterion for determining whether a previously held belief should be
accepted): Accept only what is beyond any shadow
of a doubt. Using this criterion
as his test, Descartes set about looking for first truths. QUESTIONS ON THE
1. What did
Descartes take to be required if one is to establish anything “firm and
lasting in the sciences,” and why did he think that such drastic measures are
required?
2. What would
justify rejecting an opinion?
3. What was
the foundation on which, up to the time of his meditations, Descartes claimed
he had based most of his beliefs?
4. When have
the senses been thought reliable and when unreliable?
5. Are there
any definite signs to distinguish being awake from being asleep according to
Descartes?
6. If there
were no definite signs to distinguish waking from dreaming, what would that
prove?
7. Even if
there were no definite signs to distinguish waking from dreaming, would there
still be certain things our senses tell us about that are not cast into
doubt? If not why not, if so what
would these things be?
8. What did
Descartes include in the class of “simple and universal things” from which
everything we imagine is constructed?
9. In what
respect do the sciences of physics, astronomy and medicine all differ from
those of arithmetic and geometry? 10.
Why did Descartes think that even the truths
of arithmetic and geometry are open to suspicion of possibly being false? 11.
Why did Descartes think that it would be even
more likely that I would always be deceived when performing calculations if
God does not exist than if God does exist? 12.
What would be wrong with admitting that the
existence of my own body, of the world around me, and of the truths of arithmetic
and geometry is highly probable? NOTES ON THE At the outset of Meditations I, Descartes complained
that so many false opinions had been spread about that it had become
necessary to rebuild the edifice of knowledge on new and more secure
foundations. To find such new
foundations he proposed to question the principles on which established
beliefs are based, and not to accept anything unless the principles that
justify it are beyond doubt. Since
most of what we know is based on sense experience or reason, he first
considered the reliability of these two “principles.” The results that he came up with were
devastating. Meditations I offers two powerful
arguments for doubting anything we have learned from sensory experience and
anything we have discovered by reasoning.
These arguments are commonly referred to as the dreaming argument and
the deceiver argument. a. The dreaming argument. Prior to Descartes,
philosophers wishing to question the reliability of sensory experience had
commonly appealed to a set of arguments known as the sceptical “modes.” Sceptics would employ the “modes” to show
that one and the same object can appear differently to different animals, to
different human beings, to different sense organs, to the same sense organ
under different circumstances, and so on.
This would hopefully convince the listener that we have no direct
knowledge of the nature of objects, but only of appearances, and that the
appearances of one and the same object are so numerous and different that
there is no way of telling which, if any of them is a correct representation
of the actual object. But Descartes had
little use for the sceptical modes. He
remarked that while our senses may sometimes tell us different things about
the same object, this generally only happens when the object is small or
distant. There is another, more
compelling reason to doubt what our senses tell us about the medium-sized
objects in our immediate surroundings: the possibility that we might be
dreaming. Descartes supposed
that I have no way of definitively ruling out the possibility that I might
now be asleep and dreaming. The fact
that my current experiences are rich, detailed, and vivid does not prove that
they are not dreamed up since I have in the past had dreams that are rich,
detailed and vivid. Or, at the very
least, I can well conceive it possible that I might have such a dream. Similarly, the fact that I now seem to
remember a continuous, coherent past, reaching back for many years and
consisting of events that are uniformly ordinary and law-governed does not
prove that I am not now dreaming. For,
even though many dreams are incoherent, this is not the case with all
dreams. Dreams can be as coherent as
waking experiences and sometimes they can include dreamed up memories of a
long, coherent history. At least, it
is possible that some dreams could be like this. And as long as it is possible we cannot
claim to know beyond a shadow of a doubt that dreams cannot be internally
coherent and plausible. Even the
memory of having awakened is no sure indication I am not now dreaming, since
I have had (or can well think it possible that I could have) dreams in which
I dream that I wake up from a dream within the dream. In general, it seems that any criterion
anyone might care to use to try to distinguish dreams from waking experience
could be undermined by the objection that we might just dream that the
criterion has been met. We might think that,
despite these possibilities, we are pretty good at telling the difference
between reality and dreams. But for
Descartes, being pretty good at determining the difference is not good
enough. We need to be absolutely
certain. As long as it is possible
that we might be dreaming, we cannot claim to know for sure that we are not
dreaming, even now. But if I grant that
there is no way of definitively ruling out the possibility that I am now
dreaming, then scepticism about the reliability of all sensory experience
follows as a consequence. Since things
experienced in a dream are generally false, having no good way to determine
that I am now awake means having no good way to
determine that there is any truth in my current experience. I cannot say that simply because I am
seeing this page with these words printed on it, that therefore there must
actually be a page with these words printed on it. More radically, I cannot say that simply
because I see myself surrounded by the walls of this room, in this building,
in this city, in this country, that any such room, building, city, or country
exists. There may not even be a planet
Earth or a universe like the one I now think I remember seeing when I last
looked up at the stars at night.
Perhaps I am a being on a planet in another world who is merely
dreaming all of these things and none of them actually exists, and in a
moment I will wake up and discover my error.
Indeed, perhaps there is not a corporeal, extended world of any
kind. After all, setting aside the
minority opinions of Hobbes and Epicurus, people have for centuries believed
in the possibility of the existence of immaterial spirits like ghosts and
angels. These are things that exist
without having physical bodies. What
is to say, therefore, that I might not be a sleeping angel, merely dreaming
that it has a body? This may seem a
rather extravagant supposition. But at
this stage, Descartes had to worry about extravagant suppositions. The bare possibility of being a dreaming
angel, however remote, is enough to warrant a doubt, however remote, about
whether I have a body. And according
to Descartes’s initial criterion, nothing can be
accepted as a first principle if it is open to any doubt, however
extravagant. Just as the dreaming
argument should lead me to doubt whether I really have a body, and whether
the surrounding world is at all like what I perceive it to be, so it should
lead me to doubt whether there are any such things as the atoms and
corpuscles imagined by the mechanical philosophers, or the forms and
qualities imagined by the Aristotelians, or even the other people that we all
imagine to inhabit our world.
Similarly, it should lead me to doubt whether any of the sciences that
describe these things, such as physics, cosmology, and metaphysics are true. After all, just as I may be an angel
dreaming that it has a body, so I may be an angel in an aspatial
spirit-world dreaming it is located somewhere in a world of bodies. Indeed, I may be a single, solitary spirit,
the sole thing in creation, dreaming that there is a world of extended bodies
and other minds around it. But while all of these
things — the existence of my own body, the existence of other bodies and an
external world, and even the existence of other minds — are called into
question by the dreaming argument, Descartes suggested that there are some
things that the argument might not be able to call into question. We tend to think that when we dream, our
dreams are like images of things we have seen before in waking life, only
differently arranged and perhaps distorted.
These images have to come from somewhere, and if they are nothing like
what actually exists within myself, then they cannot
come from me. If this is correct, then
even if I am now dreaming, something must exist that is in some way like what
I am dreaming of — either I myself or, if I am nothing like them, something
else. At the very least the simple
component parts that my dream images are made up of — the figures, the
motions, the sizes, and perhaps the colours — ought to be specific instances
of simple and basic things that we have encountered in reality and that must
therefore exist. Otherwise, it would be as extraordinary that we could dream
of these things as that someone blind since birth should be able to dream in
colour. If we accept that this is
impossible, then perhaps we can say that certain “simple and universal
things,” the component parts of the things that figure in our dreams and
constitute the compound things that we dream about, must be real. As examples of such
things, Descartes listed “corporeal nature in general” which he further
analyzed as consisting of extension, shape, size, number, place, and
time. This is list is remarkable for
what it fails to mention. Colour, scent,
taste, and other sensible qualities do not appear on the list, even though
they, too, would seem to be simple and universal things. Descartes earlier described the “simple and
universal things” using the metaphor of “true colours” that make things up
the way the colours in oils make up the pictures made by painters. But when he came to list the simple and
universal things, colour was not included.
It is only in Meditations
III that we get any explanation of the reasons for this quiet omission. A little more
reflection led Descartes to note that there are certain things that we know
about the “simple and universal things.” Shape and number are among the
“simple and universal things.” And our
reason appears to reveal a number of truths to us that are specific to the
nature of shapes and numbers. These
truths constitute the sciences of geometry and arithmetic. Interestingly, they do not make any claims
about what shapes and numbers might be used to describe the things that
actually exist. They just tell us
about the nature of shape and number themselves. Consequently, the truths of geometry and
arithmetic are not affected by the dreaming argument, which only casts doubt
on our knowledge of what exists around us.
If I dream of five objects, then it might be that those five objects
do not exist and that my experience is in that sense false. But my dream itself, insofar as it consists
of five objects, will have to consist of a group of three objects and a group
of two other objects (at least, of objects that could be grouped in this
way). So the simple truth of
arithmetic that two plus three is equal to five will have to be reflected in
my dream. This is not to say
that when I dream of five objects I will always think that those objects can
be divided into a group of two objects and a group of three objects. After all, we sometimes make mistakes in
simple arithmetic even in waking life, as anyone who has tried to add a
column of numbers knows, so it should certainly be possible to make the same
mistakes in our dreams. But generally,
such mistakes are a product of haste and inattention and so can be cured by
following the 4th rule of the method. This would put us in a position to accept
the propositions of geometry and arithmetic as true of the objects we
experience, whether those experiences be mere images in dreams or actual
sense experiences of external things. A slow and careful analysis of numbers
and shapes, assisted by frequent review of our work, should uncover the
truths of arithmetic and geometry, whether we perform that analysis while
awake or while asleep. Thus, these
truths of pure reasoning at least appear to be immune to the doubt caused by
the dreaming argument. b. The deceiver argument. However,
Descartes proceeded to entertain even more radical sceptical doubts. It is possible that in his younger days he
may have attended the Loudun witchcraft trials and
been impressed by the efforts of the defence attorneys to argue that if the
Devil is as powerful as the Prosecution claimed he is, then he ought to be
able to deceive the Court and the Judges into thinking that innocent people
are witches. Whether that is the case
or not, the thought occurred to him that, if a being powerful enough to have
created the world exists, then that being ought to easily be able to tinker
with the way our minds work. With this possibility
in mind, Descartes returned to the troublesome fact noted at the close of the
last section: that we sometimes make errors in calculation. We think that we can correct these errors
by simply checking and rechecking our calculations. But what, Descartes asked, if there is a
demon deceiver out there who ensures that every time I add two to three I
come up with the same, wrong result? A
really powerful deceiver should be able to convince me that two plus three is
six. After all, I do occasionally make
this mistake all on my own, so a deceiver should be able to make me make it
systematically, and so foul up my entire knowledge of arithmetic. This may be an
extravagant possibility, but for Descartes, as long as there is the least
reason for doubting a claim, however wild or extravagant, we cannot accept
that claim. And so, our reasoning in
geometry and mathematics must be rejected as well as our sense experience of
ourselves and the world around us. There is an important
sub-text to what Descartes said about the dreaming and deceiver arguments. He suggested that, dubitable though they
may be, our intuitions about simple natures, and the demonstrative sciences
of mathematics and geometry that we are able to build on these intuitions,
are relatively more immune to doubt than our beliefs about an external
world. It takes a more powerful
argument, the deceiver argument, to call the former claims into doubt. Over the remainder of
the Meditations Descartes repaired
the destructive work done in Meditations
I, first by identifying a solid foundation for knowledge and then by
successively readmitting into the edifice of knowledge the things cast into
doubt by the dreaming and deceiver arguments.
It should be no surprise that he managed to rehabilitate our clear and
distinct perceptions of simple and universal things, and the demonstrative
sciences of arithmetic and geometry that are based on those perceptions,
before he managed to rehabilitate the belief in an external world or in the
existence of our own bodies. Meditations
I teaches us that the latter beliefs are open to
doubts that do not affect the former.
But we will also see that when Descartes rehabilitated old knowledge
claims, he did so only in an attenuated form: the objects of our knowledge
turn out to be stripped of their sensible qualities and a degree of
uncertainty ends up attaching even to our knowledge of their “primary and
real” qualities. ESSAY QUESTIONS AND RESEARCH PROJECTS
1. Was
Descartes entitled to claim that there is no way to distinguish waking from
dreaming?
2. Was Descartes
entitled to claim that the truths of arithmetic and geometry are not called
into doubt by the dreaming argument?
3. Could a
deceiver who systematically deceives me, and ensures that I never come across
any evidence of my mistake, really be a deceiver?
4. Is there
anything that escapes the doubts cast on sense experience and reasoning by
the dreaming and the deceiver arguments? |
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