## 1. The Simplicity of the "Argument"




One of the hallmarks of Descartes' version of the ontological
argument is its simplicity. Indeed, it reads more like the report of an
intuition than a formal proof. Descartes underscores the simplicity of
his demonstration by comparing it to the way we ordinarily establish
very basic truths in arithmetic and geometry, such as that the number
two is even or that the sum of the angles of a triangle is equal to the
sum of two right angles. We intuit such truths directly by inspecting
our clear and distinct ideas of the number two and of a triangle. So,
likewise, we are able to attain knowledge of God's existence simply by
apprehending that necessary existence is included in the clear and
distinct idea of a supremely perfect being. As Descartes writes in the
Fifth Meditation:



> [1] But if the mere fact that I can produce from my thought
> the idea of something entails that everything which I clearly and
> distinctly perceive to belong to that thing really does belong to it,
> is not this a possible basis for another argument to prove the
> existence of God? Certainly, the idea of God, or a supremely perfect
> being, is one that I find within me just as surely as the idea of any
> shape or number. And my understanding that it belongs to his nature
> that he always exists is no less clear and distinct than is the case
> when I prove of any shape or number that some property belongs to its
> nature (AT 7:65; CSM 2:45).




One is easily misled by the analogy between the ontological argument
and a geometric demonstration, and by the language of
"proof" in this passage and others like it. Descartes does
not conceive of the ontological argument on the model of an Euclidean or
axiomatic proof, in which theorems are derived from epistemically
prior axioms and definitions. On the contrary, he is drawing our
attention to another method of establishing truths that informs our
ordinary practices and is non-discursive. This method employs
intuition or, what is the same for Descartes, clear and distinct
perception. It consists in unveiling the contents of our clear and
distinct ideas. The basis for this method is the rule for truth, which
was previously established in the Fourth Meditation. According to the
version of this rule invoked in the Fifth Meditation, whatever I
clearly and distinctly perceive to be contained in the idea of
something is true of that thing. So if I clearly and distinctly
perceive that necessary existence pertains to the idea of a supremely
perfect being, then such a being truly exists.




Although Descartes maintains that God's existence is ultimately
known through intuition, he is not averse to presenting formal versions
of the ontological argument. He never forgets that he is writing for a
seventeenth-century audience, steeped in scholastic logic, that would
have expected to be engaged at the level of the Aristotelian syllogism.
Descartes satisfies such expectations, presenting not one but at least
two separate versions of the ontological argument. These proofs,
however, are stunningly brief and betray his true intentions. One
version of the argument simply codifies the psychological process by
which one intuits God's existence, in the manner described above:



> **Version A**: 
> 
> 1. Whatever I clearly and distinctly perceive to be contained in the
> idea of something is true of that thing.
> 2. I clearly and distinctly perceive that necessary existence is
> contained in the idea of God.
> 3. Therefore, God exists.
> 
> 
> 




The rule for truth appears here in the guise of the first premise,
but it is more naturally read as a statement of Descartes' own
alternative method of "demonstration" via clear and distinct perception
or intuition. In effect, the first "premise" is designed to instruct
the meditator on how to apply this method, the same role that the
analogy with a geometric demonstration serves in passage [1].




When presenting this version of the argument in the First Replies,
Descartes sets aside this first premise and focuses our attention on
the second. In so doing, he is indicating the relative unimportance of
the proof itself. Having learned how to apply Descartes' alternative
method of reasoning, one need only perceive that necessary existence
pertains to the idea of a supremely perfect being. Once one attains
this perception, formal arguments are no longer required; God's
existence will be self-evident (Second Replies, Fifth Postulate; AT
7:163-4; CSM 2:115).




Descartes sometimes uses traditional arguments as heuristic devices,
not merely to appease a scholastically trained audience but to help
induce clear and distinct perceptions. This is evident for example in
the version of the ontological argument standardly associated with his
name:



> **Version B**: 
> 
> 1. I have an idea of supremely perfect being, i.e. a being having all
> perfections.
> 2. Necessary existence is a perfection.
> 3. Therefore, a supremely perfect being exists.
> 
> 
> 




While this set of sentences has the surface structure of a formal
argument, its persuasive force lies at a different level. A meditator
who is having trouble perceiving that necessary existence is contained
in the idea of a supreme perfect being can attain this perception
indirectly by first recognizing that this idea includes every
perfection. Indeed, the idea of a supremely perfect being just is the
idea of a being having all perfections. To attempt to exclude any or
all perfections from the idea of a supremely being, Descartes observes,
involves one in a contradiction and is akin to conceiving a mountain
without a valley (or, better, an up-slope without a down-slope). Having
formed this perception, one need only intuit that necessary existence
is itself a perfection. It will then be clear that necessary existence
is one of the attributes included in the idea of a supremely perfect
being.




While such considerations might suffice to induce the requisite
clear and distinct perception in the meditator, Descartes is aiming a
deeper point, namely that there is a conceptual link between necessary
existence and each of the other divine perfections. It is important to
recall that in the Third Meditation, in the midst of the causal
argument for the existence of God, the meditator already discovered
many of these perfections -- omnipotence, omniscience, immutability,
eternality, simplicity, etc. Because our mind is finite, we normally
think of the divine perfections separately and "hence may not
immediately notice the necessity of their being joined together" (First
Replies, AT 7:119; CSM 2:85). But if we attend carefully to "whether
existence belongs to a supremely perfect being, and what sort of
existence it is" we shall discover that we cannot conceive any one of
the other attributes while excluding necessary existence from it
(ibid.).




To illustrate this point Descartes appeals to divine omnipotence. He
thinks that we cannot conceive an omnipotent being except as existing.
Descartes' illustration presupposes the traditional, medieval
understanding of "necessary existence." When speaking of
this divine attribute, he sometimes uses the term
"existence" *simpliciter* as shorthand. But in his
more careful pronouncements he always insists on the phrase
"necessary and eternal existence," which resonates with
tradition. Medieval, scholastic philosophers often spoke of God as the
sole "necessary being," by which they meant a being who
depends only on himself for his existence. This is the notion of
"aseity" or self-existence (*a se esse*). Since
such a being does not depend on anything else for its existence, he
has neither a beginning nor an end, but is eternal. Returning to the
discussion in the First Replies, one can see how omnipotence is linked
conceptually to necessary existence in this traditional sense. An
omnipotent or all-powerful being does not depend ontologically on
anything (for if it did then it would not be omnipotent). It exists by
its own power:



> [2] when we attend to immense power of this being, we shall
> be unable to think of its existence as possible without also
> recognizing that it can exist by its own power; and we shall infer from
> this that this being does really exist and has existed from eternity,
> since it is quite evident by the natural light that what can exist by
> its own power always exists. So we shall come to understand that
> necessary existence is contained in the idea of a supremely perfect
> being .... (*ibid*.)




Some readers have thought that Descartes offers yet a third version of
the ontological argument in this passage (Wilson, 1978, 174-76), but
whether or not that was his intention is unimportant, since his
primary aim, as indicated in the last line, is to enable his meditator
to intuit that necessary existence is included in the idea of
God. Since there is a conceptual link between the divine attributes, a
clear and distinct perception of one provides a cognitive route to any
of the others.




Although Descartes sometimes uses formal versions of the ontological
argument to achieve his aims, he consistently affirms that God's
existence is ultimately known through clear and distinct perception.
The formal versions of the argument are merely heuristic devices, to be
jettisoned once one has attained the requisite intuition of a supremely
perfect being. Descartes stresses this point explicitly in the Fifth
Meditation, immediately after presenting the two versions of the
argument considered above:



> [3] whatever method of proof I use, I am always brought
> back to the fact that it is only what I clearly and distinctly perceive
> that completely convinces me. Some of the things I clearly and
> distinctly perceive are obvious to everyone, while others are
> discovered only by those who look more closely and investigate more
> carefully; but once they have been discovered, the latter are judged to
> be just as certain as the former. In the case of a right-angled
> triangle, for example, the fact that the square on the hypotenuse is
> equal to the square on the other two sides is not so readily apparent
> as the fact that the hypotenuse subtends the largest angle; but once
> one has seen it, one believes it just as strongly. But as regards God,
> if I were not overwhelmed by philosophical prejudices, and if the
> images of things perceived by the senses did not besiege my thought on
> every side, I would certainly acknowledge him sooner and more easily
> than anything else. For what is more manifest than the fact that the
> supreme being exists, or that God, to whose essence alone existence
> belongs, exists? (AT 7:68-69; CSM 2:47)




Here Descartes develops his earlier analogy between the (so-called)
ontological argument and a geometric demonstration. He suggests that
there are some meditators for whom God's existence is immediately
manifest; for them God's existence is akin to an axiom or definition in
geometry, such as that the hypotenuse of a right triangle subtends its
largest angle. But other meditators, whose minds are confused and mired
in sensory images, must work much harder, and might even require a
proof to attain the requisite clear and distinct perception. For them,
God's existence is akin to the Pythagorean Theorem. The important point
is that both kinds of meditators ultimately attain knowledge of God's
existence by clearly and distinctly perceiving that necessary existence is
contained in the idea of supremely perfect being. Once one has achieved
this perception, God's existence will be manifest or, as Descartes says
elsewhere, "self-evident" (*per se notam*) (Second Replies,
Fifth Postulate; AT 7: 164; CSM 2:115).




Descartes' contemporaries would have been surprised by this last
remark. While reviewing an earlier version of the ontological argument,
Aquinas had rejected the claim that God's existence is self-evident, at
least with respect to us. He argued that what is self-evident cannot be
denied without contradiction, but God's existence can be denied.
Indeed, the proverbial fool says in his heart "There is no God" (Psalm
53.1).




When confronted with this criticism by a contemporary objector,
Descartes tries to find common ground: "St. Thomas asks whether
existence is self-evident as far as we are concerned, that is, whether
it is obvious to everyone; and he answers, correctly, that it is not"
(First Replies, AT 7:115; CSM 2:82). Descartes interprets Aquinas to be
claiming that God's existence is not self-evident *to everyone*,
which is something with which he can agree. Descartes does not hold
that God's existence is immediately self-evident, or self-evident to
everyone, but that it can become self-evident to some careful and
industrious meditators.


## 2. The Distinction between Essence and Existence




In the Fifth Meditation and elsewhere Descartes says that God's
existence follows from the fact that existence is contained in the
"true and immutable essence, nature, or form" of a
supremely perfect being, just as it follows from the essence of a
triangle that its angles equal two right angles. This way of putting
the *a priori* argument has puzzled commentators and has led to
a lively debate about the ontological status of Cartesian essences and
the objects which are purported to "have" them. Some
commentators have thought that Descartes is committed to a species of
Platonic realism. According to this view, some objects that fall
short of actual existence nevertheless subsist as abstract, logical
entities outside the mind and beyond the physical world (Kenny, 1968;
Wilson, 1978). Another commentator places Cartesian essences in God
(Schmaltz 1991), while two recent revisionist interpretations
(Chappell, 1997; Nolan, 1997) read Descartes as a conceptualist who
takes essences to be ideas in human minds.




Descartes' reference to "essences" raises another important issue
more directly related to the ontological argument. In claiming that
necessary existence cannot be excluded from the essence of God,
Descartes is drawing on the traditional medieval distinction between
essence and existence. According to this distinction, one can say
*what* something is (i.e. its essence), prior to knowing whether
it exists. So, for example, one can define what a horse is --
enumerating all of its essential properties -- before knowing whether
there are any horses in the world. The only exception to this
distinction was thought to be God himself, whose essence just is to
exist. It is easy to see how this traditional distinction could be
exploited by a defender of the ontological argument. Existence is
included in the essence of a supremely perfect being, but not in the
essence of any finite thing. Thus it follows solely from the essence of
the former that such a being actually exists. At times, Descartes
appears to support this interpretation of the ontological argument. In
the Fifth Replies, for example, he writes that "the existence of a
triangle should not be compared with the existence of God, since the
relation between existence and essence is manifestly quite different in
the case of God from what it is in the case of the triangle. God is his
own existence, but this is not true of the triangle" (AT 7:383; CSM
2:263). But Descartes' complete view is subtler and more sophisticated
than these remarks first suggest. Understanding this view requires a
more careful investigation of the distinction between essence and
existence as it appears in medieval sources. Although one often speaks
of the "traditional" distinction, the exact nature of the relation
between essence and existence in finite things was the subject of a
fierce debate among medieval philosophers. Seeing where Descartes'
position fits within this debate will provide a deeper understanding of
his version of the ontological argument.




The distinction between essence and existence can be traced back as
far as Boethius in the fifth century. It was later developed by
Islamic thinkers such as Avicenna. But the issue did not become a
major philosophical problem until it was taken up by Aquinas in the
thirteenth century. The issue arose not as part of an effort to
establish God's existence on *a priori* grounds (as mentioned
above, Aquinas was one of the staunchest critics of the ontological
argument), but out of concern to distinguish God from finite spiritual
entities such as angels. Like many scholastic philosophers, Aquinas
believed that God is perfectly simple and that created beings, in
contrast, have a composite character that accounts for their finitude
and imperfection. Earthly creatures are composites of matter and form
(the doctrine of hylomorphism), but since purely spiritual beings are
immaterial, Aquinas located their composite character in the
distinction between essence and existence.




Some of the details of Aquinas' account will emerge from our
discussion below. The primary interest of his theory for our purposes,
however, is that it led to a lively debate among his successors both as
to how to interpret the master and about the true nature of the
relation between essence and existence in created things. This debate
produced three main positions:


1. The Theory of Real Distinction
2. The Intermediate Position
3. The Theory of Rational Distinction




Proponents of the first view conceived the distinction between essence
and existence as obtaining between two separate things. In the eyes of
many Thomists, this view was considered to be quite radical,
especially as an interpretation of Aquinas' original position. The
latter is sometimes expressed by saying that essence and existence are
"principles of being" rather than beings themselves. One
problem then with the theory of real distinction, at least as espoused
by many of Aquinas' followers, was that it reified essence and
existence, treating them as real beings in addition to the created
entity that they compose.




The theory of real distinction was also considered objectionable for
philosophical reasons. Following Aquinas, many participants in the
debate urged that essence and existence are related to each other as
potency and act, so that existence can be said to
"actualize" essence. On the theory of real distinction,
this view leads to an infinite regress. If an essence becomes actual
only in virtue of something else -- *viz.* existence
-- being superadded to it, then what gives existence its reality,
and so on *ad infinitum*? (Wippel, 1982, 393f).




In response to these difficulties some scholastic philosophers
developed a position at the polar extreme from the theory of real
distinction. This was the view that there is merely a rational
distinction or a "distinction of reason" between essence
and existence in created beings. As the term suggests, this theory
held that essence and existence of a creature are identical in reality
and distinguished only within our thought by means of reason. Needless
to say, proponents of this theory were forced to distinguish purely
spiritual entities from God on grounds other than real
composition.




Giving up the doctrine of real composition seemed too much for another
group of thinkers who were also critical of the theory of real
distinction. This led to the development of a number of intermediate
positions, including Duns Scotus' curious notion of a formal
distinction and the view that essence and existence are modally
distinct such that existence constitutes a mode of a thing's
essence.




Like Francisco Suarez, his most immediate scholastic
predecessor, Descartes sides with the proponents of a rational
distinction between essence and existence. His position is unique,
however, insofar as it springs from a more general theory of
"attributes". Articulating this theory in an important
passage in the
*Principles of Philosophy*, Descartes claims that there is
merely a distinction of reason between a substance and any one of its
attributes or between any two attributes of a single substance (1:62,
AT 8A:30; CSM 1:214). For Descartes' purposes, the most significant
instance of a rational distinction is that which obtains between a
substance and its essence -- or what he sometimes refers to as its
"principal attribute" (1:53, AT 8A:25; CSM 1:210). Since thought and
extension constitute the essence of mind and body, respectively, a mind
is merely rationally distinct from its thinking and a body is merely
rationally distinct from its extension (1:63, AT 8A:31; CSM 1:215). But
Descartes insists that a rational distinction also obtains between any
two attributes of a substance. Since existence qualifies as an
attribute in this technical sense, the essence and existence of a
substance are also distinct merely by reason (1:56, AT 8A:26; CSM
1:211). Descartes reaffirms this conclusion in a letter intended to
elucidate his account of the relation between essence and
existence:



> [4]... existence, duration, size, number and all
> universals are not, it seems to me, modes in the strict sense
> .... They are referred to by a broader term and called attributes
> ... because we do indeed understand the essence of a thing in one
> way when we consider it in abstraction from whether it exists or not,
> and in a different way when we consider it as existing; but the thing
> itself cannot be outside our thought without its existence
> .... Accordingly I say that shape and other similar modes are
> strictly speaking modally distinct from the substance whose modes they
> are; but there is a lesser distinction between the other attributes
> .... I call it a rational distinction .... (To an unknown
> correspondent, AT 4:349; CSMK 3:280)




Indications are given here as to how a rational distinction is
produced in our thought. Descartes explains that we regard a single
thing in different abstract ways. Case in point, we can regard a thing
as existing, or we can abstract from its existence and attend to its
other aspects. In so doing, we have distinguished the existence of a
substance from its essence within our thought. Like scholastic
proponents of the theory of rational distinction, however, Descartes
is keen to emphasize that this distinction is purely
conceptual. Indeed, he goes on to explain that the essence and
existence of a substance are "in no way distinct" outside
thought (AT 4:350; CSMK 3:280). In reality they are identical.




While borrowing much from scholasticism, Descartes' account is
distinguished by its scope of application. He extends the theory of
rational distinction from created substances to God. In general, the
essence and the existence of a substance are merely rationally
distinct, and hence identical in reality.




This result appears to wreak havoc on Descartes' ontological
argument. One of the most important objections to the argument is that
if it were valid, one could proliferate such arguments for all sorts of
things, including beings whose existence is merely contingent. By
supposing that there is merely a rational distinction between essence
and existence abroad in all things, Descartes seems to confirm this
objection. In general, a substance is to be identified with its
existence, whether it is God or a finite created thing.




The problem with this objection, in this instance, is that it
assumes that Descartes locates the difference between God and creatures
in the relation each of these things bears to its existence. This is
not the case. In a few important passages, Descartes affirms that
existence is contained in the clear and distinct idea of every single
thing, but he also insists that there are different grades of
existence:



> [5] Existence is contained in the idea or concept of every
> single thing, since we cannot conceive of anything except as existing.
> Possible or contingent existence is contained in the concept of a
> limited thing, whereas necessary and perfect existence is contained in
> the concept of a supremely perfect being (Axiom 10, Second Replies; AT
> 7:166; CSM 2:117).




In light of this passage and others like it, we can refine the
theory of rational distinction. What one should say, strictly speaking,
is that God is merely rationally distinct from his *necessary*
existence, while every finite created thing is merely rationally
distinct from its *possible* or *contingent* existence.
The distinction between possible or contingent existence on the one
hand, and necessary existence on the other, allows Descartes to account
for the theological difference between God and his creatures.




Now, when Descartes says that a substance (be it finite or infinite)
is merely rationally distinct from its existence, he always means an
actually existing substance. So how are we to understand the claim that
a finite substance is merely rationally distinct from its
*possible* existence? What is meant by "possible (or contingent)
existence"? It is tempting to suppose that this term means non-actual
existence. But as we saw already with the case of necessary existence,
Descartes does not intend these terms in their logical or modal senses.
If "necessary existence" means ontologically independent existence,
then "possible existence" means something like *dependent*
existence. After all, Descartes contrasts possible existence not with
actual existence but with necessary existence in the traditional sense.
This account is also suggested by the term "contingent." Created things
are contingent in the sense that they depend for their existence on
God, the sole independent being.




This result explains why Descartes believes that we cannot
proliferate ontological arguments for created substances. It is not
that the relation between essence and existence is any different in God
than it is in finite things. In both cases there is merely a rational
distinction. The difference is in the grade of existence that attaches
to each. Whereas the concept of an independent being entails that such
a being exists, the concept of a finite thing entails only that it has
dependent existence.




Looking back at the problematic passage cited above from the Fifth
Replies, it becomes clear that Descartes intended something along
these lines even there. He says that "the existence of a
triangle should not be compared with the existence of God",
reinforcing the point that it is the kind of existence involved that
makes God unique. And just before this statement, he writes, "in
the case of God necessary existence...applies to him alone and
forms a part of his essence as it does of no other thing". Later
he adds: "I do not ... deny that possible existence is a
perfection in the idea of a triangle, just as necessary existence is
perfection in the idea of God" (AT 7:383; CSM 2:263). Descartes'
final position then is that essence and existence are identical in all
things. What distinguishes God from creatures is his grade of
existence. We can produce an ontological argument for God, and not for
finite substances, because the idea of a supremely perfect being
uniquely contains necessary -- or ontologically independent
-- existence.


## 3. Objections and Replies




Because of its simplicity, Descartes' version of the ontological
argument is commonly thought to be cruder and more obviously fallacious
than the one put forward by Anselm in the eleventh century. But when
the complete apparatus of the Cartesian system is brought forth, the
argument proves itself to be quite resilient, at least on its own
terms. Indeed, Descartes' version is superior to his predecessor's
insofar as it is grounded in a theory of innate ideas and the doctrine
of clear and distinct perception. These two doctrines inoculate
Descartes from the charge made against Anselm, for example, that the
ontological argument attempts to define God into existence by
arbitrarily building existence into the concept of a supremely perfect
being. In the Third Meditation, the meditator discovers that her idea
of God is not a fiction that she has conveniently invented but
something native to the mind. As we shall see below, these two
doctrines provide the resources for answering other objections as
well.




Given our earlier discussion concerning the non-logical status of
the ontological argument, it may seem surprising that Descartes would
take objections to it seriously. He should be able to dismiss most
objections in one neat trick by insisting on the non-logical nature of
the demonstration. This is especially true of the objection that the
ontological argument begs the question. If God's existence is
ultimately self-evident and known by a simple intuition of the mind,
then there are no questions to be begged. Unfortunately, not all of the
objections to the ontological argument can be dismissed so handily, for
the simple reason that they do not all depend on the assumption that we
are dealing with a formal proof.




Although it is often overlooked, many of the best known criticisms
of the ontological argument were put to Descartes by official objectors
to the *Meditations*. He in turn responded to these objections
-- sometimes in lengthy replies -- though many contemporary readers
have found his responses opaque and unsatisfying. We can better
understand his replies and, in some cases, improve upon them by
appealing to discussions from previous sections.




One classical objection to the ontological argument, which was first
leveled by Gaunilo against Anselm's version of the proof, is that it
makes an illicit logical leap from the mental world of concepts to the
real world of things. The claim is that even if we were to concede that
necessary existence is inseparable from the idea of God (in Kant's
terms, even if necessary existence were analytic of the concept "God"),
nothing follows from this about what does or does not exist in the
actual world. Johannes Caterus, the author of the First Set of
Objections to the *Meditations*, puts the point as follows:



> [6] Even if it is granted that a supremely perfect being
> carries the implication of existence in virtue of its very title, it
> still does not follow that the existence in question is anything actual
> in the real world; all that follows is that the concept of existence is
> inseparably linked to the concept of a supreme being. So you cannot
> infer that the existence of God is anything actual unless you suppose
> that the supreme being actually exists; for then it will actually
> contain all perfections, including the perfection of real existence (AT
> 7:99; CSM 2:72).




To meet this challenge, Descartes must explain how he "bridges" the
inferential gap between thought and reality. The principle of clear and
distinct perception is intended to do just that. According to this
principle, for which he argues in the Fourth Meditation, whatever one
clearly and distinctly perceives or understands is true -- true not
just of ideas but of things in the real world represented by those
ideas. Thus, Descartes' commitment to the principle of clear and
distinct perception allows him to elude another objection that had
haunted Anselm's version of the argument.




The previous objection is related to another difficulty raised by
Caterus. In order to illustrate that the inference from the mental to
the extra-mental commits a logical error, critics have observed that if
such inferences were legitimate then we could proliferate ontological
arguments for supremely perfect islands, existing lions, and all sorts
of things which either do not exist or whose existence is contingent
and thus should not follow *a priori* from their concept. The
trick is simply to build existence into the concept. So, while existence
does not follow from the concept of lion as such, it does
follow from the concept of an "existing lion."




Descartes' actual reply to this objection, which he took very
seriously, is highly complex and couched in terms of a theory of "true
and immutable natures." We can simplify matters by focusing on its key
elements. One of his first moves is to introduce a point that we
discussed earlier **(**see passage [5] in section 2),
namely that existence is contained in the idea of every thing that we
clearly and distinctly perceive: possible (or dependent) existence is
contained in our clear and distinct idea of every finite thing and
necessary (or independent) existence is uniquely contained in the idea
of God (AT 7:117; CSM 2:83). So for Descartes one does not have to
build existence into the idea of something if that idea is clear and
distinct; existence is already included in every clear and distinct
idea. But it does not follow that the thing represented by such an idea
actually exists, except in the case of God. We cannot produce
ontological arguments for finite things for the simple reason that the
clear and distinct ideas of them contain merely dependent existence.
Actual existence is demanded only by the idea of God, which uniquely
contains independent existence.




A natural rejoinder to this reply would be to ask about the idea of
a lion having not possible but wholly *necessary* existence. If
Descartes' method of reasoning were valid, it would seem to follow from
this idea that such a creature exists. This formulation of the
objection requires Descartes' second and deeper point, which is only
hinted at in his official reply. This is that the idea of a lion -- let
alone the idea of a lion having necessary existence -- is hopelessly
obscure and confused. As Descartes says, the nature of a lion is "not
transparently clear to us" (Axiom 10, Second Replies; AT 7:117; CSM
2:84). Since this idea is not clear and distinct, the method of
demonstration employed in the ontological argument does not apply to
it. Recall that the geometrical method of demonstration is grounded in
the principle of clear and distinct perception and consists in drawing
out the contents of our clear and distinct ideas. If an idea is not
clear and distinct then we cannot draw any conclusions from it about
things outside thought.




The key difference then between the idea of God on the one hand and
the idea of a necessarily existing lion is that the former can be
clearly and distinctly perceived. For Descartes, it is just a brute
fact that certain ideas can be clearly and distinctly perceived and
others cannot. Some critics have charged him with dogmatism in this
regard. Why should Descartes be allowed to legislate the scope of our
clear and distinct perceptions? Perhaps we can clearly and distinctly
perceive something that he could not.




Descartes cannot be saved entirely from this charge, but two
important points can be made in his defense. First, he has principled
reasons for thinking that everyone has the same set of innate or clear
and distinct ideas. When the meditator first proved God's existence in
the Third Meditation, she also established that God is supremely good
and hence no deceiver. One consequence of God's perfect benevolence is
that he implanted the same set of innate ideas in all finite minds.
Thus, Descartes feels justified in concluding that the limits of his
capacity for clear and distinct perception will be shared by
everyone.




Second, when responding to objections to the ontological argument
such as the ones considered above, Descartes typically does more than
insist dogmatically on a unique set of clear and distinct ideas. He
also tries to dispel the confusion which he thinks is at the root of
the objection. Since the ontological argument ultimately reduces to an
axiom, the source of an objection according to Descartes' diagnosis is
the failure of the objector to perceive this axiom clearly and
distinctly. Thus, Descartes devotes the bulk of his efforts to trying
to remove those philosophical prejudices which are hindering his
objector from intuiting the axiom. These efforts are not always
obvious, however. Descartes is good at maintaining the pretense of
answering criticisms to a formal proof. But his replies to Caterus'
objections to the ontological argument are best read as an extended
effort to dispel prejudice and confusion, so as to enable his reader to
intuit God's existence for himself.




Let us return for a moment to the objection that the ontological
argument slides illicitly from the mental to the extramental realm. We
have seen how Descartes responds to it, but it is related to another
objection that has come to be associated with Leibniz. Leibniz claims
that Descartes' version of the ontological argument is incomplete. It
shows merely that if God's existence is possible or non-contradictory,
then God exists. But it fails to demonstrate the antecedent of this
conditional (Robert Adams 1998, 135). To reinforce this objection, it
is sometimes observed that the divine perfections (omnipotence,
omniscience, benevolence, eternality, etc.) might be inconsistent with
one another. This objection is related to the previous one in that
the point in both cases is that Descartes' argument restricts us to
claims about the concept of God and lacks existential import. In order
to redress this issue himself, Leibniz formulates a different version
of the ontological argument (see Adams 1998, 141f).




Descartes was dead long before Leibniz articulated this criticism but
it was familiar to him from the Second Set of Objectors (Marin
Mersenne *et al*.) (AT 7:127; CSM 2:91). He replies by
appealing once again to the principle of clear and distinct
perception, which states that if something is contained in the clear
and distinct idea of something then it is not only possible but also
true of that thing in reality. (Descartes might have said that if
something is conceivable then it is possible, and a being having all
perfections is conceivable, but he has an even stronger principle at
his disposal in the rule for truth.) In effect, Descartes thinks he
has already satisfied Mersenne and Leibniz's extra condition. But
Mersenne's version of the objection goes further, urging that in order
to know with certainty that God's nature is possible, one must have an
adequate idea that encompasses all of the divine attributes and the
relations between them (ibid.) -- something that Descartes denies
that we have. Descartes responds to this criticism as follows:



> 
>  [7] For as far as our concepts are concerned there is no
>  impossibility in the nature of God; on the contrary, all the
>  attributes which we include in the concept of the divine nature are
>  so interconnected that it seems to us to be self-contradictory that
>  any one of them should not belong to God (AT 7:151; CSM
>  2:107).




It is difficult to see how this statement on its own addresses
Mersenne's criticism, but here again we can gain a better grip on what
Descartes has in mind by appealing to our earlier discussion in
section 2. We noted there that on Descartes' view there is merely a
rational distinction between a substance and each of its attributes,
and between any two attributes of a single substance. He also
maintains that God has only attributes and no modes or accidental
properties. This implies that there is merely a rational distinction
between all of the divine perfections, something that he expressly
affirms in his correspondence (see, e.g., AT 4:349; CSMK 3:280). In
the Third Meditation he also notes that "the unity, simplicity,
or the inseparability of all the divine attributes of God is one of
the most important of the perfections which I understand him to
have" (AT 7:50; CSM 2:34). So not only is there no inconsistency
between the divine perfections, but we understand that one of the most
important perfections is simplicity (contra Curley 2005), which is
just to say that in God there is no distinction between his
attributes: God's omnipotence just is his omniscience, which just is
his benevolence, etc. The very distinction between the divine
attributes is confined to our thought or reason. This then is what he
means by saying in passage [7] that the divine attributes are
"interconnected," which echoes a remark in the Third
Meditation passage concerning "the interconnection and
inseparability of the perfections" (ibid.). Descartes' responses
probably would not have satisfied Leibniz and Mersenne, but we can
appreciate how they have a fundamental basis in his philosophical
system.




Perhaps the most famous objection to the ontological argument is that
existence is not a property or predicate. Popularized by Kant, this
objection enjoys the status of a slogan known by every undergraduate
philosophy major worth her salt. In claiming that existence is
included in the idea of a supremely perfect being, along with all the
other divine attributes, Descartes' version of the argument appears to
succumb to this objection.




It is not obvious of course that existence is *not* a
predicate. To convince us of this point, Kant observes that there is
no intrinsic difference between the concept of a hundred real thalers
(coins common in Kant's time) and the concept of a hundred possible
thalers. Whenever we think of anything, we regard it *as*
existing, even if the thing in question does not actually exist. Thus,
existence does not add anything to the concept of a thing. What then
is existence if not a predicate? Kant's answer is that existence is
"merely the positing of a thing" or "the copula of a
judgment," the point being that when we say "God
exists" we are simply affirming that there is an object
answering to the concept of God. We are not ascribing any new
predicates to God, but merely judging that there is a subject, with
all its predicates, in the world (CPR:B626-27).




Kant's formulation of the objection was later refined by Bertrand
Russell in his famous theory of descriptions. He argues that
existential statements such as "God exists" are misleading
as to their logical form. While serving grammatically as a predicate,
the term "exists" in this sentence has a much different
logical function, which is revealed only by analysis. Properly
analyzed, "God exists" means "there is one (and only
one) x such that 'x is omnipotent, omniscient, etc.' is
true." Russell thinks this translation shows that, appearances
to the contrary, the statement "God exists" is not
ascribing existence to a subject, but asserting that a certain
description (in single quotes) applies to something in reality.
Russell's view is reflected in the standard modern logical treatment
of existence as a quantifier rather than a predicate.




It is widely believed that Descartes did not have a response to this
objection, indeed that he blithely assumed that existence is a
property without ever considering the matter carefully. But this is
not the case. The seventeenth-century empiricist Pierre Gassendi
confronted Descartes with this criticism in the Fifth Set of
Objections (and deserves credit for being the first to enunciate it):
"existence is not a perfection either in God or in anything
else; it is that without which no perfections can be present"
(AT 7:323; CSM 2:224). As with most of his replies to Gassendi (whom
he regarded as a loathsome materialist and quibbler), Descartes
responded somewhat curtly. But it is clear from the discussion in
section 2 that he had the resources for addressing this objection in a
systematic manner.




Before examining how Descartes might defend himself, it is important
to note that the question at issue is typically framed in non-Cartesian
terms and thus often misses its target. Both Kant and Russell for
example are interested in the logical issue of whether existence is a
*predicate*. Descartes, in contrast, was not a logician and
disparaged the standard subject-predicate logic inherited from
Aristotle. Although, as discussed above, he sometimes presents formal
versions of the ontological arguments as heuristic devices, Descartes
thought that God's existence is ultimately known through intuition.
This intuitive process is psychological in character. It is not a
matter of assigning predicates to subjects but of determining whether
the idea of a supremely perfect being can be clearly and distinctly
perceived while excluding necessary existence from it through a purely
intellectual operation. To be sure, Descartes was interested in the
*ontological* question of whether existence is a
"property" of substances. For him, however, the analogues
of properties are clear and distinct ideas and ways of regarding them,
not predicates.




Having said that, Descartes' best strategy for answering the
ontological version of the objection is to concede it, or at least
certain aspects of it. Descartes explicitly affirms Kant's point that
existence does not add anything to the idea of something (provided
that the terms "idea" and "concept" are
regarded as psychological items). Once again we should recall passage
[4] from the Second Replies: "Existence is contained in the idea
or concept of every single thing, since we cannot conceive of anything
except as existing" (Axiom 10, AT 7:166; CSM 2:117). So,
Descartes agrees with Kant that there is no conceptual difference
between conceiving of a given substance as actually existing and
conceiving it as merely possible. In the first instance one is
attending to the existence that is contained in every clear and
distinct idea, and in the other instance one is ignoring the thing's
existence without actively excluding it. He would, however, stress
another conceptual difference that Kant and other critics do not
address, namely that between the two grades of existence --
contingent and necessary. The clear and distinct ideas of all finite
things contain merely contingent or dependent existence, whereas the
clear and distinct idea of God uniquely contains necessary or wholly
independent existence (ibid.). As discussed previously, the
ontological argument hinges on this distinction.




Another intuition underlying the claim that existence is not a
property is that there is more intimate connection between an
individual and its existence than the traditional one between a
substance and a property, especially if the property in question is
conceived as something accidental. If existence were accidental, then a
thing could be without its existence, which seems absurd. It seems no
less absurd to say that existence is a property among other properties
(accidental or essential), for how can a thing even have properties if
it does not exist? Descartes shares this intuition. He does not think
that existence is a property in the traditional sense or is even
distinct from the substance that is said to bear it. Recall the view
discussed in section 2 that there is merely a rational distinction
between a substance and its existence, or between the essence and
existence of a substance. This means that the distinction between a
substance and its existence is confined to thought or reason. Human
beings, in their efforts to understand things using their finite
intellects, draw distinctions in thought that do not obtain in reality.
In reality, a substance (whether created or divine) just is its
existence.




The purpose of this defense of Descartes is not to render a verdict
as whether he has the correct account of existence, but to show that he
has a rather sophisticated and systematic treatment of what has been
one of the great bugbears in the history of philosophy. He does not
make the ad hoc assumption that existence is an attribute in
order to serve the needs of the ontological argument. Indeed, on
Descartes' view, existence is not a property in the traditional sense,
nor can one conceive of something without regarding it as existing.
Descartes' critics might not be convinced by his account of existence,
but then they have the burden of providing a better account. The focus
of the debate will then be shifted to the question of who has the
correct ontology, rather than whether the ontological argument is sound.