Comments and Criticisms on Meditation III
Clear and Distinct Perception
The Cogito is the one undubitable item that Descartes arrives at. But having reached
this certain proposition, in the second paragraph of Meditation II he goes on to claim
that it also gives him a criterion for truth. He says that what assures him of the truth
of the Cogito is that he perceives it clearly and distinctly and that, thus: a statement is
true if, and only if, it is perceived clearly and distinctly. This is Descartes criterion
At this point in his argument, he knows with certainty that he is a thinking thing. He
now has to deal with objects he once considered that he did ‘know clearly and
distinctly’ but which turned out not to be true at all - things like seeing the sky and the
stars which, he has argued, turn out not to be directly perceived. You do not see stars
directly; rather, you apprehend the mental images of stars in your mind. His mistakes
have been due to trusting his sense experiences which can deliver ‘obscure and
Instead of relying on his senses then, Descartes can only rely on his thinking alone.
The Cogito has given him a criterion for truth because it is a self-evident proposition:
just by inspecting it, one is forced to accept it as true. Here we might put Descartes
on pause and ask about self-evident propositions.
There are 3 points that need making:
self-evidence is subjective
propositions are self-evident only if they are known directly
propositions are self-evident only if they are clear and distinct.
The first point is that what is self-evident to one person may not be self-evident to
another. Descartes uses phrases like ‘it seems to me to be most manifest’ and ‘I am so
persuaded’ which reflect this subjectivity. And there is a difference between a
proposition seeming self-evident and being self-evident. Descartes’ criterion for truth
is itself a proposition and does not seem to be self-evident (it hardly forces itself upon
us so that we cannot even imagine how it might be doubted). Therefore, there is no
reason for anyone else besides Descartes to accept his criterion.
The second point, that self-evident propositions are known directly, refers to
propositions whose truth one is immediately aware of without any other thinking
going on, without other knowledge being employed. An example would be the
Cogito: we see it must be true without having to deduce or infer it from anything else.
Philosophers call such clarity and distinctness a phenomenological property of
propositions. Descartes assumes one can see a proposition is clear and distinct merely
by inspecting it, that it has an objective quality such that everyone will be struck by it
to the same degree. What he does not do is give an indication as to how vivid the
proposition must be to render it equally clear and distinct to everyone. It would seem
that there are indeed degrees of clarity and distinctness - we talk of ‘pretty clear’, ‘not
very clear’ and ‘absolutely clear’ which, again, all serve to indicate a more subjective
element than the objectivity Descartes has asserted. Further, it seems arguable that a
proposition becomes more clear and distinct the more one thinks about it: in other
words, these are not necessarily permanent and unchanging features of propositions.
This in turn leads us to think that it is at least possible that a clear and distinct
proposition might be false - and this doesn’t fit with Descartes’ assertion.
The principle objection to Descartes criterion for truth is the narrowness of the third
point: there are many more things that one can rationally believe to be true that are not
self-evident. A couple of such things would be that ‘All people eventually die’ and ‘I
wrote ‘All people eventually die’ just now’. Neither of these is self-evidently true but
it is hard to imagine living a normal sort of life without these beliefs, and many more
like them, being true. In short, unlike the Cartesian project of setting knowledge on
indubitable foundations, it is legitimate to wish for many other sorts of (non-self-
evident) beliefs to be foundational too.
Pressing play, Descartes admits that it ain’t all plain sailing yet. Perhaps the Cogito,
mathematical concepts like 2 + 3 = 5, and logical concepts like ‘I cannot both exist
and not exist’, are true because they are entirely mental (unlike those ‘obscure and
confused’ ideas arising from our sense experiences)? Well no, says Rene, I could be
deceived even about these by some malign spirit. Even though they are so logically
compelling, to really establish the criterion of truth Descartes needs to prove both that
God exists and that He is not a deceiver. A tall order, but RD is up for it...
Proof that God exists
As we have seen, Descartes so far is sure of just two main things: that he is a thinking
thing, and that he has a criterion for truth (clear and distinct perception). What he
needs now is to show that what he thinks is true is actually true. To do this, he needs
to prove that there is not some evil demon manipulating his mind. He needs to prove
that there is a God.
For Descartes, God is not just an epistemological luxury (something we could do
without): God’s existence is necessary for any secure knowledge at all. It is worth re-
emphasising his ambition in the Meditations: to overthrow the usual idea that things
are as they appear (as empiricism demands) and to persuade us that our habitual
inferences from our sensations are not just untrustworthy – they are wrong. What
Descartes demands is that we must work from our understanding outwards if we are
to gain knowledge we can trust. To work outwards from the Cogito to knowledge of
the world a trustworthy bridge is required. Only God fits the bill.
The proof that comes up in this Meditation is a variation of the cosmological
argument for the existence of God: it is generally known as the Trademark Argument.
You will remember that the basic premises of the argument are:
1. I have in mind ideas such as animals, men, angels and a God.
2. There is at least as much reality in a cause as in its effect.
3. The idea of God contains infinity (as in ‘infinitely powerful’ etc.)
4. I have not originated the concept of infinity.
Therefore, 5. The idea of infinity in my mind has been caused by something outside
Therefore, 6. This extra-mental thing has ultimately been caused by the Greatest
Descartes himself replies to some of the possible objections to some of these
premises. Firstly, perhaps my idea of an infinite being is merely derived from
negating the idea of finiteness that I find in myself? Descartes says no, because I
could not recognise infinity except by comparison with something already in mind.
Also, infinity is not merely a negative idea: I have an idea of more reality in the
infinite being than in any finite one. Secondly, perhaps the source of the concept of
God arose from me alone like the secondary qualities of heat and cold do? This
Descartes rules out on the grounds that the idea of God, unlike that of the secondary
qualities, is clear and distinct – there is no possibility of his being mistaken about it.
Thirdly, perhaps my own mind is potentially infinite and, since I am conscious of
gradual increases in my knowledge, these may be extrapolated to the idea of an
infinite being? Descartes denies this possibility by observing that these gradual
advances come nowhere near the actual infinity that belongs to God in my
conception: what is potentially infinite cannot produce from itself the idea of
something that is actually infinite.
In all of this there is a certain plausibility. The general principle on which Descartes
is relying is ex nihilo nihil fit: things do not spring into existence from nowhere. An
objection here is that this is not known or knowable a priori [as it should be if we are
to know it indubitably as required for Descartes’ argument] and so cannot do the work
Descartes requires of it. (This objection, according to Kant, is one that no variation of
the cosmological argument can resist – which is why the Ontological Argument for
God’s existence is necessary.) However it does supply a reasonable starting point on
which we can place some reliance.
The most serious objection to the argument is one that Descartes has already
anticipated: the idea of perfection or infinity that I have is not an adequate one. A
more natural source for an explanation of this can be derived from the extrapolation
from experience: a perfect straight line can be imagined once one has grasped that one
example of a line is finer and straighter than another, and so on. Thus Descartes is
simply wrong in claiming that ‘in some way I possess the perception of the infinite
before that of the finite’.
Further, there is an implausibility in the causation process between actual things and
ideas of things. Could the idea of solidity have to be caused by something akin to a
solid idea? Why should ideas be ‘less real’ than ‘real’? Descartes offers nothing
which might help resolve this. Indeed, as a rationalist, it might be more consistent to
have the mental as superior to the physical.
Descartes’ argument fails because the genuine question about the source of the idea of
God as an infinitely perfect being can be answered by reference to natural materials
and ordinary ways of thinking. [The other genuine question, of what brings about
such an idea, can similarly be explained by an appeal to ordinary psychology rather
than divine revelation.]
A Cartesian Circle?
Having established (to his own satisfaction, at least) that God exists, Descartes can
now trust that what he perceives clearly and distinctly is not just certain: it is true.
Granting that Descartes proof of God’s existence is sound, it seems that he has argued
in a circle. [Circular arguments are ones which lack foundations and so do not
provide satisfactory explanations. A simple example of such an argument would be
‘The sky is blue because is reflects the blue sea. The sea is blue because it reflects the
blue sky.’ This ‘explanation’ is no explanation at all of the blue of the sky.] It seems
that Descartes has argued for the following:
‘I am certain that God exists because I can be certain of whatever I perceive clearly
and distinctly. I am certain of whatever I perceive clearly and distinctly because I am
certain God exists.’
The objection that he had argued in a circle was one to which Descartes himself
replied. What he said was that the ideas that the evil demon could be feeding his
mind could only be doubted if the conclusions they give rise to stem from the
memory. He acknowledged that the memory can be flawed but claimed that we
cannot doubt a proof while it is actively before our mind. Thus, our inability to doubt
while in the grip of a distinct perception makes the evil demon hypothesis irrelevant –
and if we attend carefully to the proof that God exists we will thus reach the
conclusion that God exists and is a guarantor of truth.
This is not a satisfactory answer because he has not addressed the crucial issue of how
we can know any propositions at all prior to proving the existence of God: his
observation that there are certain moments when we cannot for the moment doubt is