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Descartes on God and
His Existence
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 TAs
none
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Bibliographical Resources (reminder):
Descartes’ Meditations (with Critics and Replies) +
Discourse free at:
http://www.earlymoderntexts.com/f_descarte.html
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Leibniz’s Nouveau Essays free at:
http://www.earlymoderntexts.com/f_leibniz.html
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Further bibliography on Descartes:
Cottingham J. (1986). Descartes. Blackwell, Oxford
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Further bibliography on/by Chomsky:
Chomsky N. (2000). New Horizons in the Study of
Language and Mind. Cambridge UP: Cambridge
McGilvray J. (1999). Chomsky: Language, Mind, and Politics.
Polity Press: Cambridge
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The following can also be useful
Antony L. M. & Hornstein N. (eds.) (2003).
Chomsky and His Critics. Blackwell: Oxford
Smith, N. (1999) Chomsky: Ideas and Ideals.
Cambridge UP: Cambridge
Wilson C. (2003). Descartes’s Meditations: An
Introduction. Cambridge UP: Cambridge
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The Need of God

Main Goal: To discover the fundamental ideas
and notions, the innate truths, that God
implemented in us.

God’s Existence: Descartes proposed a causal
explanation, but the effects he focuses on are
entirely within the mind.
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The Trademark Argument

God has placed within us the idea of
himself as a craftsman’s stamp on his
work.
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This argument presents four phases:
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1.
To make an inventory of the ideas
found within oneself. The chief idea
Descartes founds is the one of a
supreme God, eternal, infallible,
omnipotent and the creator of all
things that exist a part of Himself.
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
I decided to inquire into the source of my ability to think of
something more perfect than I was; and I recognized very clearly
that this had to come from some nature that was in fact
more perfect. … it was manifestly impossible to get this [idea]
of a being more perfect than my own. For it was manifestly
impossible to get this from nothing; and I could not have
got it from myself since it is no less contradictory that the
more perfect should result from the less perfect, and depend
on it, than something should proceed from nothing. So there
remained only the possibility that the idea had been put into
me by a nature truly more perfect than I was and even
possessing in itself all the perfections of which I could have any
idea, that is—to explain myself in one word—by God. (Discourse
on the Method; CSM I: 128)
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2. The Causal Adequacy Principle.
It’s the self-evident principle that there
must be as much reality in the efficient
and total cause that there is in the effect
of that cause: ex nihilo nihil fit.
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
[T]he objective reality of our ideas needs a cause which
contains this reality not merely objectively but formally or
eminently. It should be noted that this axiom is one which
we must necessarily accept, since on it depends our
knowledge of all things, whether they are perceivable
through the senses or not. How do we know, for example,
that the sky exists? Because we see it? But this ‘seeing’
does not affect the mind except in so far as it is an idea—
I mean an idea which resides in the mind itself, not an
image depicted in the corporeal imagination. Now the
only reason why we can use this idea as a basis for the
judgement that the sky exists is that every idea must
have a really existing cause of its objective reality;
and in this case we judge that the cause is the sky itself.
And we make similar judgements in other cases. (Second
Set of Replies; CSM II: 116-7)
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3. The Causal Adequacy Principle also
applies to the realm of ideas and the
features depicted by them (ideas are often
conceived along images).
E.g. if an idea X depicts/represents an object
which is F, then the cause of the idea must
itself contain at least as much F-ness as it must
be found/represented in the idea X.
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4. Given (1), i.e. that I have an idea of God
being eternal, omnipotent, benevolent,
etc. it follows from (2) and (3) that:
The cause of my idea must contain in
itself all the features represented by
my ideas.
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Since I am a finite and imperfect being I
cannot myself be the cause of this idea
representing perfection, omnipotence, etc.
The ultimate cause of my idea of God
must be something possessing all these
perfections represented in my idea.
Thus God exists.
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
Ideas are images
Thoughts are about things as images are
images of things.
Some of my thoughts are as it were the images of
things, and it is only in these cases that the term
‘idea’ is strictly appropriate—for example, when I
think of a man, or a chimera, or the sky, or an angel, or
God. (Third Meditation; CSM II: 25)
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Ideas, as images, cannot in themselves be
false.
Now as far as ideas are concerned, provided they
are considered solely in themselves and I do not
refer them to anything else, they cannot strictly
speaking be false; for whether it is a goat or a
chimera that I am imagining, it is just as true
that I imagine the former as the latter. (Third
Meditation; CSM II: 26)
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
Causal Adeq. Princ. + Ideas as images 
God
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
the effect of that cause. For where, I ask, could the effect
get its reality from, if not from the cause? And how could
the cause give it to the effect unless it possessed it? It
follows from this both that something cannot arise from
nothing, and also that what is more perfect—that is,
contains in itself more reality—cannot arise from what is
less perfect. … if we suppose that an idea contains something
which was not in its cause, it must have got this from nothing;
yet the mode of being by which a thing exists objectively <or
representatively> in the intellect by way of an idea, imperfect
though it may be, is certainly not nothing, and so it cannot come
from nothing. (Third Meditation; CSM II: 28-9)
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[I]deas in me are like <pictures, or> images which can
easily fall short of the perfection of the things from
which they are taken, but which cannot contain
anything greater or more perfect. (Third Meditation;
CSM II: 29)
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Hierarchy of Ideas
(i) idea of God
(ii) idea of finite substances
(iii) idea of accident and modes
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
Because of the Causal Adequacy Principle:
Descartes can argue that ideas of things less
perfect than myself can be wholly
invented/created by myself whereas ideas of
things more perfectly than myself cannot be
wholly created/invented by myself.
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The idea of God is neither an
(i) an adventitious idea (coming from the senses)
(ii) nor invented.
It is simply found within the mind and yet it
corresponds to something outside the mind.
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The Idea of God is innate
It is innate, for if it cannot be caused by an
external thing and yet corresponds to an
external thing.
As such it must be stamped into the mind
at the first instance of its existence.
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By the word ‘God’ I understand a substance that is
infinite, <eternal, immutable,> independent,
supremely intelligent, supremely powerful, and
which created both myself and everything else (if
anything else there be) that exist. All these attributes are
such that, the more carefully I concentrate on them, the
less possible it seems that they could have
originated from me alone. So from what has been
said it must be concluded that God necessarily exists.
It is true that I have an idea of substance in me in
virtue of the fact that I am a substance; but this
would not account for my having the idea of an
infinite substance, when I am finite, unless this
idea proceeded from some substance which really
was infinite. (Third Meditation; CSM II: 31)
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
Descartes does not discuss Marsenne’s assertion
that there are human beings with no innate idea
of God:
[T]he fact that the native of Canada, the Hurons and
other primitive people, have no awareness of any idea
of this sort seems to establish that the idea does come
from previous held notions. (Marsenne; Second Set of
Objections; CSM II: 89)

Furthermore Descartes does not tackle the
question how there can be natural atheists if the
idea of God is innate.
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God as Final Cause

Problem with Causal Adequacy
Principle
The Causal Adequacy Principle does not seem to
account for new or emergent properties.
E.g. the property of sponginess created in
mixing and backing some flowers emerge from
some chemical changes.
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
Idea of God?
Hobbes (Third Set of Objections with Replies;
CSM2: 127) objected that we cannot have an
idea of God.
For, if ideas are images what is our image of
God?
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Hobbes:
But when I think of an angel, what comes to mind is an
image, now of a flame, now of a beautiful child with
wings; I feel sure that this image has no likeness to
an angel, and hence that it is not the idea of an
angel. But I believe that there are invisible and
immaterial creatures who serve God … In the same
way we have no idea or image corresponding to the
sacred name of God. … It seems, then, that there is
no idea of God in us. (Third Set of Objections with
Replies; CSM II: 126-7
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Descartes’ reply
Although ideas may be somewhat like picture or
images they’re not actually images
‘idea’ stands for what is immediately perceived
by the intellect.
One can know and understand something
without fully grasping it.
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Descartes’ Reply
Here my critic wants the term ‘idea’ to be taken to
refer simply to the images of material things which
are depicted in the corporeal imagination … I am
taking the word ‘idea’ to refer to whatever is
immediately perceived by the mind. (Third Set of
Objections with Replies; CSM II: 127)
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The Ontological Argument

It is an a priori proof of God’s existence.
One can imagine a triangle even if this figure
were not to exist anywhere outside one thought.
To do so it suffices to imagine that it has tree
angles whose sum is 180 degrees, and so on.
Thus we can deduce that a triangle has an essence
whether or not it exists outside our mind.
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The same (a priori reasoning) with God
We can imagine his existence because the latter
cannot be separated from his essence.
It would be contradictory to think of God (a
supremely perfect being) lacking existence.
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Lack of existence entails imperfection.
Since I must attribute all perfections to God
and since existence is among the perfections,
God cannot lack it.
Descartes’ argument rests on the very idea that
existence, like omniscience and omnipotence, is
a perfection. If so it should be a property of
some kind.
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But, is existence a property?
Cf., for instance, Frege’s view that existence is a
second order predicate.
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Importance of the Argument for God’s
Existence
It constitutes the only way we can transcend the
subjective self-awareness knowledge and
progress to the knowledge of the external world
and reality.
Thus within the Cartesian framework God can
be viewed as a scientific posit/necessity.
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The Avoidance of Error
We should recognize the impossibility for God
to deceive.
Yet we often do make mistakes.
It seems thus that there should be evil in the
world.
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How do we conciliate the presence of error with
the idea that God is perfect and benevolent?
To avoid error we should suspend most of our
judgements. We should restrict them to the
sphere of pure mathematics, which is the only
reliable strategy for avoiding error.
Mathematical judgements constitute the
paradigm of properties that the intellect can
clearly and distinctly perceive.
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Why mathematics?
Mathematical judgements help understanding
reality insofar as ordinary three-dimensional
objects can be defined in pure mathematical
terms.
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The physical nature is the proper subject of
mathematical reasoning.
When we make errors we improperly embrace a
proposition without having sufficient grounds
for doing so. And we do so because the scope
of our will transcend the scope of the intellect:
So what then is the source of my mistake? It must be
this: the scope of the will is wider than that of the
intellect; but instead of restricting it with the same
limits, I extend its use to matter I do not understand.
(Fourth Meditation; CSM II: 40)
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
Cartesian Circle
To prove God’s existence I need to trust my
intellect.
Yet without prior knowledge of God’s
existence I have in principle no reason to trust
my intellect.
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If all knowledge depends on God, then to know
this premise (that all knowledge depends on
God) one needs to prove the existence of God
without first knowing God.
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It is only on relying on clear and distinct ideas
that Descartes can proves the existence of God,
yet it is only by the existence of God that one
can have clear and distinct ideas.
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Out of the circle?
The way out of the circle is for Descartes to
claim that there are certain propositions (e.g.
cogito) presenting self-evident knowledge that
one can grasp as long as one is attending them.
These self-evident propositions do not require
God’s intervention.
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The Need of God
Why on top of the self-evident elementary truth
we need God?
Because of the temporary nature of these selfguaranteeing truths, i.e. because they last only as
long as one is entertaining them.
Once God’s existence in established we can
progress beyond the temporality of these selfevident truths.
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