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How does Descartes try to extricate himself from the


sceptical doubts that he has raised? Does he succeed?
[All page references and quotations from the Meditations
are taken from the 1995 Everyman edition]
In the Meditations, Descartes embarks upon what Bernard
Williams has called the project of 'Pure Enquiry' to
discover certain, indubitable foundations for knowledge. By
subjecting everything to doubt Descartes hoped to discover
whatever was immune to it. In order to best understand how
and why Descartes builds his epistemological system up from
his foundations in the way that he does, it is helpful to
gain an understanding of the intellectual background of the
17th century that provided the motivation for his work.
We can discern three distinct influences on Descartes,
three conflicting world-views that fought for prominence in
his day. The first was what remained of the mediaeval
scholastic philosophy, largely based on Aristotelian
science and Christian theology. Descartes had been taught
according to this outlook during his time at the Jesuit
college La Fleché and it had an important influence on his
work, as we shall see later. The second was the scepticism
that had made a sudden impact on the intellectual world,
mainly as a reaction to the scholastic outlook. This
scepticism was strongly influenced by the work of the
Pyrrhonians as handed down from antiquity by Sextus
Empiricus, which claimed that, as there is never a reason
to believe p that is better than a reason not to believe p,
we should forget about trying to discover the nature of
reality and live by appearance alone. This attitude was
best exemplified in the work of Michel de Montaigne, who
mockingly dismissed the attempts of theologians and
scientists to understand the nature of God and the universe
respectively. Descartes felt the force of sceptical
arguments and, while not being sceptically disposed
himself, came to believe that scepticism towards knowledge
was the best way to discover what is certain: by applying
sceptical doubt to all our beliefs, we can discover which
of them are indubitable, and thus form an adequate
foundation for knowledge. The third world-view resulted
largely from the work of the new scientists; Galileo,
Copernicus, Bacon et al. Science had finally begun to
assert itself and shake off its dated Aristotelian
prejudices. Coherent theories about the world and its place
in the universe were being constructed and many of those
who were aware of this work became very optimistic about
the influence it could have. Descartes was a child of the
scientific revolution, but felt that until sceptical
concerns were dealt with, science would always have to
contend with Montaigne and his cronies, standing on the
sidelines and laughing at science's pretenses to knowledge.
Descartes' project, then, was to use the tools of the
sceptic to disprove the sceptical thesis by discovering
certain knowledge that could subsequently be used as the
foundation of a new science, in which knowledge about the
external world was as certain as knowledge about
mathematics. It was also to hammer the last nail into the
coffin of scholasticism, but also, arguably, to show that
God still had a vital rôle to play in the discovery of
Meditation One describes Descartes' method of doubt. By its
conclusion, Descartes has seemingly subjected all of his
beliefs to the strongest and most hyberbolic of doubts. He
invokes the nightmarish notion of an all-powerful, malign
demon who could be deceiving him in the realm of sensory
experience, in his very understanding of matter and even in
the simplest cases of mathematical or logical truths. The
doubts may be obscure, but this is the strength of the
method - the weakness of criteria for what makes a doubt
reasonable means that almost anything can count as a doubt,
and therefore whatever withstands doubt must be something
epistemologically formidable.
In Meditation Two, Descartes hits upon the indubitable
principle he has been seeking. He exists, at least when he
thinks he exists. The cogito (Descartes' proof of his own
existence) has been the source of a great deal of
discussion ever since Descartes first formulated it in the
1637 Discourse on Method, and, I believe, a great deal of
misinterpretation (quite possibly as a result of Descartes'
repeated contradictions of his own position in subsequent
writings). Many commentators have fallen prey to the
tempting interpretation of the cogito as either syllogism
or enthymeme. This view holds that Descartes asserts that
he is thinking, that he believes it axiomatic that
'whatever thinks must exist' and therefore that he
logically concludes that he exists. This view, it seems to
me, is wrong. It should be stated on no occasion, in the
Meditations, does Descartes write 'I am thinking, therefore
I am', nor anything directly equivalent. Rather, he says:
"Doubtless, then, that I exist.and, let him deceive me as
he may, he can never bring it about that I am nothing, so
long as I shall be conscious that I am something. So that
it must, in fine, be maintained, all things being maturely
and carefully considered, that this proposition I am, I
exist, is necessarily true each time it is expressed by me
or conceived in my mind." (p. 80).
The point here is that it is impossible to doubt the truth
of the proposition 'I exist' when one utters it. It is an
indubitable proposition, and one that will necessarily be
presupposed in every attack of the sceptic. Descartes is
not yet entitled to use syllogisms as the possibility of
the malign demon is still very much alive. As an aside,
Descartes himself denies that the cogito is a syllogism,
although it should be mentioned that in some of the Replies
to Objections he seems to assert that it is in fact a
syllogism. Finally, in the Regulae ad directionem ingenii,
Descartes denies the usefulness of syllogisms as a means to
I believe that, given Descartes' project, it is fair to
grant him that the cogito deserves the status he bestows
upon it. For can there be anything more certain than
something that is so forceful and so powerful that every
time it is presented to our mind we are forced to assent to
What Descartes did here was to jiggle about the way
philosophy normally approaches the construction of
knowledge structures. By starting with self-knowledge, he
elevates the subjective above the objective and forces his
epistemology to rest upon the knowledge he has of his own
self (and inadvertently sets the tone for the next 300
years of philosophy). This leaves him with a problem. He
can know his own existence, that he is a thinking thing and
the contents of his consciousness, but how can any of this
ever lead to any knowledge of anything outside of himself?
The answer is that, by itself, it can't. Descartes, in the
third Meditation, attempts to prove the existence of God,
defined as a being with all perfections. This proof is to
be derived from his idea of a God, defined as a being with
all perfections. So far, so good - Descartes examines the
contents of his consciousness and discovers within it this
idea, and we can allow him this. At this point, however, he
introduces a whole series of scholastic principles
concerning different modes of causation and reality without
proper justification:
"For, without doubt, those [ideas considered as images, as
opposed to modes of consciousness] that represent
substances are something more, and contain in themselves,
so to speak, more objective reality, that is, participate
by representation in higher degrees of being or perfection
than those that represent only modes or accidents; and
again the idea by which I conceive a God.has certainly in
it more objective reality than those ideas by which finite
substances are represented. Now it is manifest by the
natural light that there must be at least as much reality
in the efficient and total cause as in its effect; for
whence can the effect draw its reality if not from its
cause? And how could the cause communicate to it this
reality unless it possessed it in itself?"
Whence do these principles draw their indubitability? Even
if we grant that it is contrary to natural reason that an
effect can have greater 'reality' than its cause, that the
concepts of modes and substances are coherent with
Descartes' method, let alone possess the properties that he
ascribes to them, then surely we can still bring the malign
demon into play? Is it not possible that this all- powerful
demon could bring it about that Descartes has a notion of a
being with all possible perfections that he calls God? No,
says Descartes, because the notion (representing something
perfect) would then have more objective reality than the
demon (as something evil and thus imperfect) has formal
reality, and 'it is manifest by the natural light' that
this is not possible. But why not? Maybe the demon has just
made it seem impossible, and it seems that Descartes has no
answer to this.
Further problems remain. Cosmological arguments for God
invoking the notion of causation have always had to contend
with the problem of the cause of God. For if all events (or
ideas) are caused ultimately by God, then what about God
Himself? Why should He be exempt from this rule? The
standard response to this is to claim that God, being
omnipotent, causes Himself. One of the chief perfections
that Descartes attributes to God is that of
'self-existence', that is, that His existence depends on
nothing else but itself. But if we examine this idea, it
seems a little confused. If God is the efficient cause of
God then we are forced to ask how something that does not
yet exist can cause anything. If God is the formal cause of
God, i.e. it is part of the intrinsic nature of God that he
exists - which seems more likely - then it seems that we
have merely a reformulation of the ontological argument for
God's existence from Meditation 5.
It seems that Descartes may have anticipated the wealth of
criticism that the causal proof of God would inspire, and
so, after explaining how human error and a benevolent,
non-deceiving God are compatible in Meditation Four, he
produced in Meditation Five a version of the mediaeval
ontological argument for God's existence. Unlike the causal
argument, the ontological argument doesn't involve the
covert import of any new principles. It simply purports to
show that, from an analysis of his own idea of God,
Descartes can show that He necessarily exists. The
reasoning goes like this:
I have ideas of things which have true and immutable
natures. If I perceive clearly and distinctly that a
property belongs to an idea's true and immutable nature,
then it does actually belong to that nature. I perceive
clearly and distinctly that God's true and immutable nature
is that of a being with all perfections. Further, I
perceive clearly and distinctly that existence is a
perfection and non-existence a non- perfection. Thus
existence belongs to God's true and immutable nature. God
One of the interesting things about this argument is that,
at first sight, it does not seem to depend in any way upon
anything that has been proved hitherto. It is an
application of pure logic, an analysis of what we mean when
we say 'God' and a inference from that analysis. Descartes
explicitly says that an idea's true and immutable nature
does not in any way depend upon his thinking it, and thus
upon his existence. Once he has perceived clearly and
distinctly that an idea's true and immutable nature
consists in such-and-such, that is the case whether or not
he thinks it is, or even if he exists or not. Descartes in
fact recognises the primacy of the ontological argument:
"although all the conclusions of the preceding Meditations
were false, the existence of God would pass with me for a
truth at least as certain as I ever judged any truth of
mathematics to be." If this is true, which it seems to be,
then this argument is only as trustworthy as the faculties
which enabled us to construct it, which are the same
faculties that enable us to know mathematical truths, and
so it seems worthwhile to ask how, under Descartes' theory,
we come to know mathematical truths. Descartes claims we
perceive them clearly and distinctly. How do we know that
what we perceive clearly and distinctly is true? Because
God, being perfect, is no deceiver, and would not let it be
the case that we could ever perceive something clearly and
distinctly without it being the case. It seems then, that
this proof of God, relying on the veracity of clear and
distinct ideas, relies on the certain knowledge that a
non-deceiving God exists. We have another proof of God, the
causal proof as described in Meditation three. But apart
from the patent futility of using one proof of p to
construct another proof of p, on examining the causal proof
of God further, we find that it, too, relies upon a
methodology that can only be relied upon if the divine
guarantee is present, for if this guarantee is not present,
then, as I mentioned above, how can we be sure that the
all-powerful demon is not exercising his malignant
This, of course, is the infamous Cartesian circle, first
identified by Arnauld in the Fourth Objections and
discussed ever since. Many philosophers have tried to get
Descartes off the hook in various ways, some by denying
that there is a circle and some by admitting the
circularity but denying its significance. I will here
briefly evaluate a few of their arguments.
Some commentators have taken a passage from Descartes'
reply to the Second set of Objections (Mersenne's) to
indicate that Descartes is only actually interested in the
psychological significance of fundamental truths. The
passage is as follows:
"If a conviction is so firm that that it is impossible for
us ever to have any reason for doubting what we are
convinced of, then there are no further questions for us to
ask; we have everything we could reasonably want."
Under my interpretation, this is what it is about the
cogito that makes it so important for Descartes, so we
cannot have any argument with the principle expressed by
him in the above passage. But can it help break the circle?
When we clearly and distinctly perceive something,
Descartes says, fairly I think, that this perception
compels our assent, that we cannot but believe it. God's
rôle in the system, to these commentators, is as a
guarantor of our memory regarding clarity and distinctness.
In other words, once we have proved God's existence, we can
happily know that any memory we have of a clear and
distinct idea regarding x is true i.e. that we really did
have a clear and distinct idea of x. But this does not seem
satisfactory, as we still do not have a divine guarantee
for the reasoning that leads us from the clear and distinct
notions we originally have about God to the proof of His
existence. We can give assent to the clear and distinct
notions we have originally; in fact, we are compelled to
give this assent when the notions are presented to our
mind, but the logical steps we take from these ideas to the
final proof is still subject to the evil demon because God
is not yet proven. Furthermore, because these steps are
needed, the memory of the original clear and distinct ideas
are themselves subject to doubt because God is not yet
proven. It seems that the only way either of the proofs of
God could be accepted would be if we had an original clear
and distinct perception of God directly presented to our
mind (qualitatively similar to the cogito). But this in
itself would make any future proofs redundant.
Interestingly, this sounds quite similar to a divine
Harry Frankfurt, in his book 'Demons, Dreamers and Madmen',
has argued that what Descartes is actually looking for is a
coherent, indubitable set of beliefs about the universe.
Whether they are 'true' or not is irrelevant. Perfect
certainty is totally compatible with absolute falsity. Our
certainty may not coincide precisely with 'God's' truth,
but should this matter?:
"Reason.can give us certainty. It can serve to establish
beliefs in which there is no risk of betrayal. This
certainty is all we need and all we demand. Perhaps our
certainties do not coincide with God's truth.But this
divine or absolute truth, since it is outside the range of
our faculties and cannot undermine our certainties, need be
of no concern to us." (Frankfurt, p 184)
This is almost a Kantian approach to knowledge, where we as
humans only concern ourselves with the phenomena of objects
as they present themselves to us, not with the objects in
themselves. Can we ascribe this view to Descartes? It's
tempting, given what we have said above regarding the prime
importance of indubitability, but it would seem that a God
presenting ideas to us in a form which doesn't correspond
to reality, and then giving us a strong disposition to
believe that they do correspond to reality would be a
deceiving God and contrary to Descartes' notion of Him.
Thus the belief set would not be coherent. Perhaps, as we
do not have clear and distinct ideas of the bodies we
perceive, and as the divine guarantee only extends as far
as clear and distinct ideas, we are being too hasty in
judging that reality is how it appears to be and if we
stopped to meditate further we would see that reality is
actually like something else. But aside from the fact that
this seems unlikely, Descartes never seemed to envisage the
So much for the Cartesian circle. Where does this leave the
ontological argument, which we had only just begun to
discuss? Aside from the methodological difficulties, there
do seem to two further problems with it. The first has been
noted by almost every student of Descartes over the years -
that of the description of existence as a property. Put
briefly, this objection states that existence is not a
property like 'red' or 'hairy' or 'three-sided' that can be
applied to a subject, and thus it makes no sense to say
that existence is part of something's essence. If we assert
that x is y, we are already asserting the existence of x as
soon as we mention it, prior to any application of a
predicate. from the beginning. In other words, to say 'x
exists' is to utter a tautology and to say that 'x doesn't
exist' is to contradict oneself. So how can sentences of
the form 'x doesn't exist' make sense? one may well ask. It
is because these sentences are shorthand for 'the idea I
have of x has no corresponding reality' and it was to solve
problems like this that Bertrand Russell constructed his
theory of descriptions. To add existence to an idea doesn't
just make it an idea with a new property, it changes it
from an idea into an existent entity.
Finally, if Descartes is right, there seems no reason why
we cannot construct any other idea whose essence includes
existence. For instance, if I conjure up the idea of 'an
existent purple building that resembles the Taj Mahal',
then it is the true and immutable nature of this idea that
it is a building, that this building resembles the Taj
Mahal, that the building is purple, and that it exists. But
no such building does exist, as far as I am aware, and if
it did exist, its existence would not be necessary, but
contingent. This in itself is enough, I think, to show that
the ontological argument is false.
Once we have destroyed Descartes' proofs of the existence
of God, the edifice of knowledge necessarily comes tumbling
down with them, as we find that almost everything Descartes
believes in is dependent on God's nature as a non-deceiver:
"I remark.that the certitude of all other truths is so
absolutely dependent on it, that without this knowledge it
is impossible ever to know anything perfectly." (p.115)
The only possible exceptions are those assent-compelling
beliefs such as the cogito. Even these, however, are
doubtful when we are not thinking about them, and the above
passage does give weight to Edwin Curley's argument that:
"Descartes would hold that the proposition "I exist" is
fully certain only if the rest of the argument of the
Meditations goes through. We must buy all or nothing."
This is not the end of the story, though. As far as
Descartes is concerned, by the end of Meditation Five, he
has produced two powerful proofs of God, has a clear and
distinct notion of his own self, has a criterion for truth,
knows how to avoid error and is beginning to form ideas
regarding our knowledge of corporeal bodies.. And so it
remains only to explain why we are fully justified in
believing in corporeal bodies, and also to draw the ideas
of Meditation Two regarding self-knowledge to their full
Regarding the nature of corporeal bodies and our knowledge
of them, it seems to me that, given his premises, the
conclusions Descartes draws in Meditation Six are generally
the correct ones. He again invokes the causal to argue that
the ideas of bodies we have within our minds must be caused
by something with at least as much formal reality as the
ideas have objective reality. We could theoretically be
producing these ideas, but Descartes dismisses this
possibility for two reasons - firstly, that the idea of
corporeality does not presuppose thought and secondly that
our will seems to have no effect on what we perceive or
don't perceive. (This second argument seems to me to ignore
dreaming, in which what we perceive derives from us but is
independent of our will). The ideas, then, could come from
God, or from another being superior to us but inferior to
God. But this, too, is impossible, argues Descartes, as if
it were the case that God produces the ideas of bodies in
us, then the very strong inclination we have towards
believing that the idea-producing bodies resemble the ideas
we have would be false and thus God would be allowing us to
be deceived which is not permissible. The same would apply
if any other being were producing these ideas. Thus,
concludes Descartes, it is most likely that our ideas of
corporeal bodies are actually caused by bodies resembling
those ideas. We cannot be certain, however, as we cannot
claim to have clear and distinct notions of everything we
perceive. We can, however, claim certainty with regard to
those properties of bodies which we do know with clarity
and distinction; namely, size, figure (shape), position,
motion, substance, duration and number (not all of these
assertions are justified). Obviously we cannot claim that
we know these properties for specific bodies with clarity
and distinction, for to do so would leave open the question
of why it is that astronomy and the senses attribute
different sizes to stars. What Descartes means is that we
can be sure that these primary qualities exist in bodies in
the same way that they do in our ideas of bodies. This
cannot be claimed for qualities such as heat, colour, taste
and smell, of which our ideas are so confused and vague
that we must always reserve judgement. (This conclusion is
actually quite similar to the one John Locke drew fifty
years later in his Essay Concerning Human Understanding.)
I think we can grant this reasoning, with the caveat
regarding dreaming that I noted above, and of course the
other unproved reasonings that Descartes exhumes here, such
as the causal principle. Furthermore, it seems to be
further proof that Descartes does believe we can get to
know objects in themselves to a certain extent.
Finally, I turn to Descartes' argument for the distinction
of mind and body. Descartes believes he has shown the mind
to be better known than the body in Meditation Two. In
Meditation Six he goes on to claim that, as he knows his
mind and knows clearly and distinctly that its essence
consists purely of thought, and that bodies' essences
consist purely of extension, that he can conceive of his
mind and body as existing separately. By the power of God,
anything that can be clearly and distinctly conceived of as
existing separately from something else can be created as
existing separately. At this point, Descartes makes the
apparent logical leap to claiming that the mind and body
have been created separately, without justification. Most
commentators agree that this is not justified, and further,
that just because I can conceive of my mind existing
independently of my body it does not necessarily follow
that it does so. In defence of Descartes, Saul Kripke has
suggested that Descartes may have anticipated a modern
strand of modal logic that holds that if x=y, then L (x=y).
In other words, if x is identical to y then it is
necessarily identical to it. From this it follows that if
it is logically possible that x and y have different
properties then they are distinct. In this instance, that
means that because I can clearly and distinctly conceive of
my mind and body as existing separately, then they are
distinct. The argument, like much modern work on identity,
is too technical and involved to explore here in much
depth. But suffice to say that we can clearly and
distinctly conceive of Dr Jekyll and Mr. Hyde as being
distinct and yet they are identical, necessarily so under
Kripke's theory. It is doubtful that Kripke can come to
Descartes' aid here and Descartes needs further argument to
prove that the mind and the body are distinct.
And so we finish our discussion of Descartes' attempts to
extricate himself from the sceptical doubts he has set up
for himself. As mentioned previously, the ultimate
conclusion to draw regarding the success of the enterprise
that Descartes set for himself must be that he failed. When
the whole epistemological structure is so heavily dependent
on one piece of knowledge - in this case the knowledge that
God exists - then a denial of that knowledge destroys the
whole structure. All that we can really grant Descartes -
and this is certainly contentious - is that he can rightly
claim that when a clear and distinct idea presents itself
to his mind, he cannot but give his assent to this idea,
and furthermore, that while this assent is being granted,
the clear and distinct idea can be justly used as a
foundation for knowledge. The most this gets us - and this
is not a little - is the knowledge of our own existence
each time we assert it. But Descartes' project should not
be judged by us as a failure - the fact that he addressed
topics of great and lasting interest, and provided us with
a method we can both understand and utilise fruitfully,
speaks for itself.
1. Descartes, René A Discourse on Method, Meditations and
Principles of Philosophy trans. John Veitch. The Everyman's
Library, 1995.
 Descartes, René The Philosophical Writings of Descartes
volume I and II ed. and trans. John Cottingham, R.
Stoothoff and D. Murdoch. Cambridge, 1985. 
Frankfurt, Harry Demons, Dreamers and Madmen.
Bobbs-Merrill, 1970.
Curley, Edwin Descartes Against the Skeptics. Oxford, 1978.
 Vesey, Godfrey Descartes: Father of Modern Philosophy.
Open University Press, 1971. 
Sorrell, Tom Descartes: Reason and Experience. Open
University Press, 1982. 
The Oxford Companion to Philosophy ed. Ted Honderich.
Oxford University Press, 1985. 
Cottingham, John Descartes. Oxford, 1986. 
Williams, Bernard Descartes: The Project of Pure Enquiry.
Harmondsworth, 1978. 
Russell, Bertrand The History of Western Philosophy. George
Allen and Unwin, 1961. 
11. Kripke, Saul Naming and Necessity. Oxford 1980.



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