i. Idea and Simple Nature
Descartes is often considered to be the modern founder of “idealism.”
It is a questionable habit to hastily evaluate this so-called “idealism”
positively or (most of the time) negatively, without first attempting to define it. Admittedly, this task presents so many difficulties that one might be tempted to avoid it: One of the most vexing might be to attempt to discern the Cartesian definition of the idea. This ques
tion itself can be further divided into at least three more: (a) Is there a unified, coherent, and operational meaning of the term idea in Des
cartes’ texts? (b) Is this meaning unquestionably new with regard to previous meanings (i.e., in Aristotle, in medieval thinkers, in the later scholastics)? (¿-) Did this eventual innovation have any influence on later philosophers, or did it simply remain a hapax without a pos
terity? We cannot undertake to answer all these questions here;1 we shall therefore only approach the first question, for it helps settle the other two in advance, for only if Descartes presents a unified, coher
ent, and operational concept of the idea will it eventually be possible to evaluate its originality and influence, and even— if one really in
sists— to speak of “idealism.”
But the unity and coherence of the Cartesian meanings of the words idee/idea seem from the outset to be quite problematic, since they encompass two definitions: one found mostly in the Regulae ad directionem ingenii and the other mostly in the Meditations
.1
Let usfirst examine this antinomy more in detail. The Regulae seeks to theo
rize a science that would eliminate Aristotelian-Thomistic ontology,"
substituting itself as a quasi-ontology. Consequently, the Regulae re- jects idea in the sense of eidos (that is, the essence of a thing) while retaining in the new meaning of the term two traits borrowed from Aristotle.
(a) The idea is the equivalent of a figure: “figures or ideas” (AT X, 414, 1. 17); “As for figures, we have already shown how ideas of all things can be formed by means of these alone” (AT X, 450,11. 10 - 12).3 Ideas no longer represent things directly as they are perceived by our senses or as they appear to us; rather, they represent things by means of an encoding process performed by figures: Things simply consist of figures of extension in movement, which are per
ceived by the senses only because they hide their original character as figures (primary qualities) under guises that are consistent with the realm of the senses (secondary qualities). Against the sensory ap
pearances that are unaware of them, figures play the fundamental role in the idea function: For each sensation received in the mind, science must therefore recreate the intelligible and nonsensory figures
>/ that originally cause this sensation as their sensory and unintelligible effect. Figures in actuality constitute the middle term between the thing itself and the way it appears to consciousness: Primary physical figures are transmitted to the brain, which only then decodes them as sensations. Thus the figure, although mathematical and abstract, and thus bearing absolutely no resemblance to the sensation, in actu
ality constitutes the thing as such. Figures schematize the truth about / a given thing by underlying the disfiguring sensation. They thus re
place the thing itself, which they present in its original invisibility.
Hence, as figure, the idea remains real— determined by the thing itself as well as characterizing it.4
(b) The idea belongs both to the realm of the imagination and to that of the intellect: “ the idea . . . must be formed as distinctly as possible in the imagination,” “two distinct ideas in our imagination”
(AT X, 4 16 ,11. 3off. and 444, 1. 3). Similarly, the idea is “received”
in the sensus communis} Obviously, it is impossible for any and all ideas to be thus “received” and stored in common sense and in the imagination; only “ corporeal ideas” (“ idea corporea,” AT X, 419, 1.
12; 443,1. 2) may do so. Here at least, Descartes is willing to maintain the hylomorphic determination of the eidos of “physical” beings. Be
sides, it is clear here that Descartes adopts the terminology and the
matic of the faculties of the soul established by Aristotle, even if he does so only to critique them and modify them.
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In the Meditations, these two characteristics of the idea are re
versed.
(a) Now the idea, as a figure, instead of remaining a form of the thing, shapes thought itself: “ the form of any given thought”
{PW
II, 113). Here the idea still informs, but without any other raw mate
rial besides the representations that reach the imagination: “ [ideas]
only in so far as they give form to [informant] the mind itself” (AT VII, 16 0 ,11. 14 -15 ; 161, 11. 2-3). The idea shapes not a thing, as its essence or its code, but rather our mental perception of that thing, as a form of the immediate representation and no longer of what is represented: “by an idea I mean whatever is the form of a given per
ception [forma perceptionis]” (AT VII, 188,11. 14-15). The idea de
termines thought through the action of thinking, rather than de
termining the thing on the basis of its essence. It should not surprise us that ideas not only are reduced to the role of a simple mode of thought {modi cogitationis, modi cogitandif but are radically iden
tified with it: “ ideas, that is thoughts [ideae sive cogitationes], of such things” (AT VII, 35, 1. 21; PW II, 24 [modified]); “ the idea or the thought” (AT V, 354, 11. 10 -11). An idea can be summed up as thought, as a “ notion,” 7 a “ concept,” 8 or even a “sensation.” 9 We witness here an irreversible shift of the center of gravity: The idea informs the raw material— i.e., thought— rather than the matter of the thing itself.
{b) This shift is accompanied by a broadening of the perspective:
Far from being bounded by the imagination and by common sense, in which case the idea could not exist outside of the sensation, the idea becomes universally possible because it is identified with thought— and is therefore now thinkable without sensory presuppo
sition or any other presupposition besides itself. An idea is therefore anything that is informed by thought: “ the word ‘idea5 is generally taken to mean everything thought insofar as it is considered to be only some object in the understanding” ; “I use the word ‘idea5 to mean everything which can be in our thought55; “ For by ‘idea5 I do not just mean the images depicted in the imagination . . . ; instead by the term ‘idea51 mean in general everything which is in our mind when we conceive something, no matter how we conceive it.” And here Descartes does indeed seem to deduce the universality of the idea (“ I am taking the word ‘idea5 to refer to everything that is imme
diately perceived by the mind55) from the universality of the cogitatio itself (“ Thought. I use this term to include everything that is within
WHAT IS THE METHOD IN THE METAPHYSICS? 45
us in such a way that we are immediately aware of it” ).10 Further, Descartes often mentions this divergence to his correspondents: For him, and against Aristotle, the idea is defined by thought only, inde
pendently of the imagination. Whether the idea informs representa
tions of sensory or of purely intellectual origin is irrelevant here, since the information provided by thought is enough in itself to define the idea— so much so that in Descartes’ last texts innateness actually encompasses the entire field of consciousness.
Thus Descartes’ doctrine has evolved to the point that it has now inverted itself: Either an idea processes things by means of figures, or thought is informed by the idea. Ideas depend upon the imagina
tion or are freed from it on the basis of the cogitatio. Yet, even while acknowledging the gap that separates the epistemic pole established by the Regulae from the metaphysical pole anchoring the Meditations, it seems problematic to assert that Descartes simply and crudely con
tradicted himself. When an interpreter calls attention to a shortcom
ing in the author studied, the rules of fairness (and prudence) demand that he or she also consider the possibility of his or her own shortcom
ings. We will therefore suppose, as a matter of principle, that Des
cartes did not crudely contradict himself, even in the face of such variation in his theory of the idea. How can we support this supposi
tion? By considering a very straightforward hypothesis: namely, that the variations noted above, although indisputable, do not concern Descartes’ own contribution to the definition of the idea, but rather echo some of its consequences for the pre-Cartesian definitions that were prevalent at the time. But then, one may object, why did we not refer, right from the start, to this genuinely Cartesian determina
tion of the idea? Answer: because Descartes’ doctrine of the idea does not at first use the term idea. Instead, it uses a new and original substitute: namely, the simple nature.
2. The Regulae and the Forgetting of the Intellectual Simple Nature
In the Regulae, in the first part of Rule X II, Descartes characterizes
“ideas” in terms of “figures” or “ shapes” formed in the imagination (AT X, 414: CMS I, 41), thus reworking in a fairly precise, if critical, fashion the doctrines of Aristotle’s De anima. But in the second part of Rule X II, he abandons this seemingly cautious use of the tradi
tional framework and introduces an utterly new concept, that of the
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“ simple nature” (natura simplicissima, res simplex) This is not only, or primarily, a terminological innovation; what is involved is an epis- temological revolution.11
A simple nature has two characteristic features: it is neither sim
ple, nor a nature. It is, first of all, opposed to “ nature,” since in place of the thing considered in itself, according to its ousia (essence) or physis (nature), it denotes the thing considered in respect of our knowledge: “ when we consider things in the order that corresponds to our knowledge of them [in ordine ad cognitionem nostram] our view of them must be different from what it would be if it were speaking of them in accordance with how they exist in reality” (AT X, 418: CSM 1, 44). Our knowledge, then, does not apprehend things as they “really” (re vera) are, or “in their own categories,” and “in some class of being” (AT X, 381: CSM I, 21); instead, leaving aside the truth of a thing’s ousia, we apprehend the first knowable object, whatever it may be, provided it can be known “ easily” and hence with certainty. Thus, so far from antecedently determining or regu
lating our knowledge, the “natures” are simply the end products of our knowledge. The “ nature” is a “knowable object” in the sense of
“ object simply insofar as it can be known by us” ; it thus deposes traditional ousia, or essence, and banishes it once and for all from modern metaphysics (despite Leibniz’ attempts to bring it back).
In the second place, a simple nature is not “ simple” in the standard sense of the term. We are not dealing with the intrinsic simplicity of an atom or element or primary form; instead, the “ simplicity” is purely relative, referring to whatever appears most simple to the mind. For example, each body is reducible to three simple natures—
extension, shape, and movement. Yet it is no objection to say that shape could be reduced to the still simpler concepts of extension and limit; for even if the concept of limit is in itself more abstract than that of shape, this very abstractness allows it to be applied to a larger number of terms (not just extension, for example, but also duration and movement), thus making it complex from the point of view of our knowledge. The simple nature remains the simplest term, but the simplicity is an epistemological, not an ontological one: It does not relate to essence or ousia. “Hence we are concerned with things only in so far as they are perceived by the intellect, and so we term
‘simple’ only those things which we know so clearly and distinctly that they cannot be divided by the mind into others which are more distinctly known” (AT X, 418: CSM I, 44). The result is a concept WHAT IS THE METHOD IN THE METAPHYSICS? 47
of idea that is distinctly and originally Cartesian: idea defined as an object that is primary in respect of our knowledge and not in respect of its ousia or essence— primary in so far as it is “easy” to know, and not in respect of some indivisible form or eidos.
Given this definition of an idea as a simple nature, our next task is to look at Descartes’ use of the expression. Rule X I I pro
vides a detailed list of simple natures, grouped under three head
ings: (a) those that are “purely intellectual” and whose knowledge re
quires only “ some degree of rationality [nos rationis esse participes]” ; (b) those that are “ purely material” and require some contribution from the imagination; and (c) common simple natures or “ common notions [communes notiones].” This last group is subdivided into two types. First, there are those that belong to simple natures irre
spective of whether they are intellectual or material, such as exis
tence, unity, etc.; such natures are accordingly designated as “real.”
Second, there are those that allow other simple natures to be linked together— that are “ as it were links [veluti vincula quaedam]” — in virtue of being “common notions” in the Aristotelian sense; these include the fact that two terms that are themselves equal must be equal to a third term (hence the label for these natures is “logical” ).
Identified in this way, these simple natures, in the Regulae, allow us to specify the conditions of operation for mathesis universalis (Rule IV ), given the addition of a theory of order (Rules V - VII) and, to complete the account, a theory of measurement (Rule X I V) } 2
But this uniform list conceals an outcome that is in fact very far from being homogeneous. In the development of the Regulae (as in
deed will also be the case in the later Essays published with the Dis
course), the simple natures are used only in tackling strictly scientific or epistemological issues: the theory of equations, the theory of curves (in optics), the theories of “ analytic geometry,” of reflection and refraction, of magnetism, and so on. Descartes’ actual program of work would thus appear to make use only of those simple natures that are purely material, linked by the “ common” simple natures.
The intellectual simple natures, by contrast, though they are identi
fied and listed, are not put to use at all at this stage; their employment would, in effect, require reasoning of a purely intellectual kind, con
ducted in abstraction from the world of the senses— reasoning de
voted to theoretical objects that cannot be perceived by the senses and are, in the strict sense of the term, metaphysical. The program of the sciences, and its method of procedure, is quite different: Sci
48 CHAPTER THREE
ence deals with simple natures of the material kind— objects that can be apprehended only through the senses and the imagination. And even though the common notions or principles of logic apply to both the intellectual and the material domains, the mind nonetheless has to proceed quite differently according to whether its knowledge de
pends on the “ pure intellect” (“ ab intellectu puro” ) or on the intellect
“ as it intuits the images of corporeal things” (“ab eodem imagines rerum materialium intuente,” A T X, 419: CSM I, 45). The distinc
tion between simple natures that are intellectual and those that are material corresponds to the distinction between metaphysics and physics, and hence also to that between understanding and imagina
tion. This contrast, which Descartes articulated explicitly only after 1630,13 is central to his work throughout the subsequent years and is a recurring theme in the Meditations and Principles: “ the part of the mind which is of most help in mathematics, namely the imagina
tion, does more harm than good in metaphysical speculations” ; or again, “it generally happens with almost everyone . . . that if they are accomplished in metaphysics they hate geometry, while if they have mastered geometry they do not grasp what I have written on first philosophy.” 14 In short, the appearance of homogeneity that the simple natures present is specious: In reality, they belong to faculties and sciences that are radically distinct— the material simple natures, grasped by the imagination, belonging to physics and mathematics;
the intellectual simple natures, apprehended by the understanding, belonging to metaphysics. What is more, the mind must make a choice between these two areas of inquiry, since metaphysics tran
scends and is external to physics and mathematics, providing the foundations for these sciences; that indeed is its essential and defining function.
This last point could lead us to accept the following straightfor
ward claim: “ The Regulae does not therefore . . . contain any trace of metaphysics. On the contrary, the uncertainty that remains in that work about the nature of the mind, and its tendency to assume all truths under the same program, shows plainly that when he wrote the Regulae, Descartes’ thought was still operating at a purely scientific level.” 15 In this view, the function of the Regulae would be limited to constructing a theory of science, realized in mathematical and physical terms, without crossing the border into metaphysics at any point. But this thesis is immediately open to a decisive counter
example: The Regulae does refer to the purely intellectual simple na
WHAT IS THE METHOD IN THE METAPHYSICS? 49
5o CHAPTER THREE
tures, though not making any use of them, and thus already acknowl
edges the domain of thought that will later be revealed as the province of metaphysics: “ the idea which represents for us what knowledge or doubt or ignorance is, or the action of the will which may be called
‘volition,’ and the like” (AT X, 419: CSM I, 44). At the very least we have to admit that, if the Regulae does not actually unfold a Cartesian metaphysics, it nonetheless articulates its fundamental concepts and assigns them a primary importance. This in turn raises the following question: Why does Descartes not undertake to provide at least a sketch of his metaphysics in the Regulae, given that he already has the requisite conceptual materials at his disposal?
This question is doubly pressing when we observe that the Regulae takes us right up to the brink of metaphysics. It does not merely identify the intellectual simple natures (Rule X II), but also, even as early as Rule III, attempts to link one of them with a (real) common simple nature, thus hinting, even at this early stage, at propositions that are strictly metaphysical. Among the examples he gives of knowl
edge by intuition (intuitus), Descartes mentions— even before geo
metrical knowledge (the definitions of the triangle and the sphere)—
the elements of the future cogito of 1637 and 1641: “ everyone can mentally intuit that he exists, that he is thinking” (“ uniusquisque animo potest intueri, se existere, se cogitare,” AT X, 368: CSM I, 14). This clause juxtaposes an intellectual simple nature (cogitare) and a common simple nature (existere). So what more do we need here to enable us to reach the first principle of metaphysics? Nothing, except for the necessary link between these two simple natures—
the elements of the future cogito of 1637 and 1641: “ everyone can mentally intuit that he exists, that he is thinking” (“ uniusquisque animo potest intueri, se existere, se cogitare,” AT X, 368: CSM I, 14). This clause juxtaposes an intellectual simple nature (cogitare) and a common simple nature (existere). So what more do we need here to enable us to reach the first principle of metaphysics? Nothing, except for the necessary link between these two simple natures—