In the Rules for the Direction of the Mind, Descartes is primarily concerned with the development of an epistemic methodology capable of revealing the whole of knowable reality. It is important that the emphasis be placed early on the fact that it is the knowable reality, as a subset of all reality, which forms the context of this approach. And as such, the priorities which serve to distinguish methods, as more or less pure, and even the entities themselves which form the domain of relevant activity, are essentially epistemic. Certainly, the language reflects the fact that these standards and entities are taken as possessing at least as much being as any possible non-epistemic object. Indeed, the proper objects of knowledge are seen as existing more certainly and definitely than any potential ‘object’ conceived as outside the epistemic realm — though, of course, the existence of such unintelligibles is never doubted. At the core of his notion of the epistemic reality, identifying the foundation of our existence as knowers, are the simple natures. They are the basic components of intelligibility, and constitute the world by which comprehension and understanding are possible. There is nothing more real or concrete to the intellect than these epistemic entities. By recognizing their proper domain as that of the intellect, the simple natures are not thereby reduced to ambiguous non-entities of thought, or contingent apparitions of the phantasy, but are identified as beings whose existence is necessary for the possibility of thought itself.

In order to develop this notion of simple natures, both as ontologically fundamental to us as knowers and heuristically instrumental to our investigation of the knowable reality, three somewhat arbitrary categorical distinctions are made. As a text devoted to developing a practical guide for the resolution of problems, the Rules approaches the realm of the intelligible from three distinct directions: the clarification of method; the constitution of us as knowers; and, the constitution of the known as knowable. These three categories (method, knower, known) are somewhat arbitrary in that they ultimately offer one image of the epistemic reality in which we are (rather paradoxically) passive participants. The structure of method as the alignment of knower to known, the constitution of the individual with respect to judgment and understanding, and the nature of the metaphysical reality presupposed by the reality of the mind are finally representative of a single architecture of intelligibility. Of course, this tripartite distinction is not utterly arbitrary. By approaching the role of simple natures along three distinct dimensions, the peculiarities of each (dimension) are more easily separated from the reality that binds them together. And the specific choices of each dimension is the natural differentiation appropriate to the study of a two part relation such as knowledge (where there are then three kinds of descriptions of the relation: knower-as-knower; known-as-known; and, knower-to-known or known-to-knower).

Following this approach, simple natures are most fully revealed when each of these three contexts or dimensions is adequately attended to. A treatment of each as a completely separate line of enquiry is not entirely possible, as their degree of overlap is often so obvious that ignoring their mutual implications is not only hazardous in terms of the completeness of the investigation, but rationally absurd (where artificial claims of irrelevancy actively obscure the object of study). Nevertheless, roughly dividing the exploration of simple natures into these categories will be helpful.

While the issues of method pervade the text throughout, issues of the knower as knower, and the known as known are more tightly defined in isolation, and offer a fertile ground upon which we can become acquainted with the nature and role of Descartes’ building blocks of the understanding. While it is true that these two caveats are given their most explicit and sustained treatment in Rule Twelve, both are explored individually (and jointly) elsewhere prior to and following the concentrated attention afforded there. In terms of the knower, in the context of constructing the general method, the text deals explicitly with our epistemic constitution prior to Rule Twelve in Rules Three, Four, Six, Eight, and Nine (and after Rule Twelve, to some extent, in Rules Fourteen and Fifteen). The image that develops is primarily concerned with clarifying the activity of the intellect in the context of a series of knowledge related faculties: including, in addition to the intellect, the imagination, sense-perception, and memory. These faculties are divided or grouped according to a number of criterion. The intellect, imagination, and sense-perception are the instruments of knowledge (see AT X, 396)^[1], and may be active in the utilization of method with respect to knowledge (and in this context, memory is entirely passive). The imagination, sense-perception, and memory are joined, though the ‘common sense’, in the body or phantasy (see beginning of Rule Twelve, AT X, 414-415). The phantasy is further divided from the intellect by the distinction between corporeal and non-corporeal natures.

Within all of these groupings, emphasis is placed upon the degree to which each faculty contributes to or distracts from standards of intelligibility. In this context, Descartes maintains, “Within ourselves we are aware that, while it is the intellect alone that is capable of knowledge, it can be helped or hindered by three other faculties, viz. imagination, sense-perception, and memory.” (AT X, 398) Indeed, it can hardly be overemphasized that the intellect is the faculty of judgement and understanding. The intellect is that cognitive power by which apprehension occurs, and is essentially, therefore, the primary faculty in matters of truth and falsity: “... there can be no truth or falsity in the strict sense except in the intellect alone, although truth and falsity often originate from the other two modes of knowing; ...” (AT X, 396) The origins of truth and falsity reveal, from the direction of our constitution as knowers, a distinction central in the construction of Descartes’ method, as well as the underlying metaphysical epistemology. For, “there can be no falsity save in composite natures which are put together by the intellect.” (AT X, 399)

Under conditions where circumstances of falsity are to be minimized and circumstances of truth are to be maximized, our primary concern should be directed toward ensuring the overall (conceptual) integrity of such composite natures. As these composite natures are in the first place objects of the intellect (or objects in the intellect), it is useless to look to the corporeal faculties for guidance. The primary concern is for the objects of intelligibility, and these are divided between the absolute and the relative. The absolute “has within it the pure and simple nature,” (AT X, 381) whereas the relative “shares [or participates in] the same nature, or at least something of the same nature, in virtue of which we can relate it to the absolute and deduce it from the absolute in a definite series of steps.” (AT X, 382) The ‘relative’ object shares in a multiplicity of simple natures and epistemic relations. While it might appear that a problem or object which is at first obscure shares in some non-epistemic property by which its composite nature is necessarily beyond ultimate intelligibility, this would mistake the composite as something more than a product of the intellect. As such a product, it is of necessity composed ultimately of only those simple natures which are apprehended directly by the bare intellect.

The actions of the intellect are responsible for the composition of complex natures, as well as the apprehension of those simples with which such composition occurs. Such operations maintain complete intelligibility when the first occurs according to deduction and the second according to intuition. Very generally, deduction is “the inference of something as following necessarily from some other propositions which are known with certainty.” (AT X, 369) More important, however, is the operation of intuition, wherein the fundamental elements of knowledge are revealed clearly to the intellect:

By ‘intuition’ I do not mean the fluctuating testimony of the senses or the deceptive judgment of the imagination as it botches things together, but the conception of a clear and attentive mind, which is so easy and distinct that there can be no room for doubt about what we are understanding. Alternatively, and this comes to the same thing, intuition is the indubitable conception of a clear and attentive mind which proceeds solely from the light of reason. (AT X, 368)

In at least one important respect, however, it is slightly misleading to think of intuition as an act or operation of the intellect. And it is for this reason precisely that Descartes strongly identifies a distinction between intuition and deduction (or, later, enumeration):

... we are distinguishing mental intuition from certain deduction on the grounds that we are aware of a movement or a sort of sequence in the latter but not in the former, and also because immediate self-evidence [literally, ‘evident presence’] is not required for deduction, as it is for intuition; deduction in a sense gets its certainty from memory. (AT X, 370)

There is an active manifestation of intuition, appearing in Rule Nine as perspicacity, which seems to be the skilled tendency to direct the full attention of the intellect upon those aspects of a problem or complex nature which are simplest, without being distracted “by many different objects at the same time.” (AT X, 401) But intuition itself seems to be simply the passive cognition of unequivocal intelligibility. Deduction, on the other hand, and its perfected manifestation in the skill of discernment, is primarily concerned with the serial enumeration of the movements of the intellect whereby one thing (either simple or complex in nature) is inferred from another.

From this rather brief encapsulation of Descartes’ explicit treatment of the knower as such, it can be observed that the natural realm of simple natures (in terms of their direct apprehension) lies under the light of intuition. The known reality is constituted in terms of such apprehension, and is ultimately reducible to the conjunction of simple natures. Addressing the realm of the known directly, Rule Twelve offers the most direct descriptions of these simples (and their conjunctions): “... 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)

Viewed on their own accord, simple natures obtain a status apparently quite independent of the knower. They are described variously as entities, irreducibles, essences, which we as knowers stand in relation to. They appear as distinct from the knowledge they constitute. Yet, they are nowhere if not “present exactly within [the intellect] or in the corporeal imagination.” (AT X, 425) It is essential that it be recognized that no discussion of these simple natures occurs without reference to their cognitive foundation. They are entities of, and in, the intellect. They are irreducible with respect to intelligibility. They are the essential constituents of the cognitive life. They do not merely stand in relation to the intellect. In a sense, they are the intellect (or more precisely: the action of the intellect).

Earlier it seemed that intuition and deduction were, in a strict sense, the only relevant actions of the intellect with which Descartes concerns himself. How could the simple natures possibly qualify as actions in this sense? Obviously they cannot. The role that simple natures play in intellectual activity is more fundamental than the general cognitive schema suggested by these two terms. Indeed, it is by their consistent and careful use that Descartes believes the processes of intuition and deduction may reveal the meta-structure of the intellect which the simple natures constitute. Intuition, and to a lesser degree deduction, hold the key to unlocking what lies at the core of intelligibility. They unveil the intellectual activity itself, and ultimately stand in a passive relation to the only knowable reality: the mortar and bricks of the understanding. Or, upon some readings, they are only successful in guiding our attention to the bricks.

It is interesting that Descartes discovers, within his treatment of intuition, two classes of objects: simple and conjoined (among other places, he mentions this dichotomy at the bottom of 432). The notion of simples, in isolation, seems relatively straight-forward. Unfortunately, conjunctions of simples as objects of intuition, and as distinct from the simples themselves, is not so clear. Before exploring the difficulties of conjunction directly, it will be helpful to explore intuition by its connection with a less complicated class of objects.

Looking directly to simple natures, independent of whatever other proper objects of intuition there may be, a number of important features should be recognized. Perhaps the most critical, for a complete picture of how the simple natures function with respect to intuition (as a passive ‘operation’ of the intellect) is the notion of spontaneous presentation. In the beginning of Rule Twelve, as he is specifying the various conditions to which we ought to direct our attention when considering the objects of knowledge, it is clear that those objects will be discerned by finding that which “presents itself to us spontaneously.” (AT X, 411) (Importantly, a second condition proposed simultaneously to this, is “How can one thing be known on the basis of something else?” Even here, attention is given heavily both to the atoms of knowledge, as well as to their inferential connections.) Later, he makes it clear:

... the only rules we provide [for the correct apprehension of simple propositions] are those which prepare our cognitive power for a more distinct intuition of any object whatever, and for a more discerning examination of it. For these simple objects must occur to us spontaneously; they cannot be sought out.^[2] (AT X, 428)

As a direct corollary to the notion of intuition as the passive apprehension of the intellect, spontaneous presentation seems a perfectly ordinary experience. Indeed, these two notions (passive intuition and spontaneous presentation) are the two sides of a single concept. The objects of the intellect, when perfectly focused under the gaze of the mind’s eye, require no further act on the part of the intellect toward understanding. The intellect, in such a condition, need look no further (and indeed, can look no further without simultaneously abandoning intelligibility). Having reached a direct confrontation with a simple nature, the intellect is passive to its cognitive value.

This does not mean the intellect cannot attempt to act upon the bare intelligibility of a simple nature, with the intention of greater refinement or precision. It is only to suggest that such action on the part of the intellect, under conditions where intelligibility is already directly present to it, can only obscure the nature under investigation (at best), or at worst can render the nature sought utterly unintelligible.

Descartes provides an illuminating example of the sort of difficulty which occurs when such an analysis is attempted beyond the perfection of intelligibility. The action of abstraction, while possible under such conditions without a total abandonment of reason, gets us only further from simplicity:

... even if the sense of the term ‘limit’ is derived by abstraction from the notion of shape, that is no reason to regard it as simpler than shape. On the contrary since the term ‘limit’ is also applied to other things — such as the limit of a duration or a motion, etc., things totally different in kind from shape — it must have been abstracted from these as well. Hence it is something compounded out of many completely^[3] different natures, and the term ‘limit’ does not have a univocal application in all these cases. (AT X, 419)

Proper focus is brought about be the skills of perspicacity and enumeration. It is achieved when the nature under examination is without any attribute or aspect in virtue of which the whole is intelligible. A simple nature is trivially obvious to the intellect.^[4]

In addition to, and following from, the spontaneous objection to the intellect of simple natures, is the idea that, as such, simple natures are not subject to the judgment. Descartes states quite plainly, “simple natures are all self-evident and never contain any falsity.” (AT X, 420) Because the simple natures are themselves the units of comprehension, and it is through them that judgments are formed, it easily follows that judgments about them will necessarily involve the action of the intellect on them (in the same way that abstraction is possible across a number of simple natures). Such judgments may be rightly formed, or mistakenly applied. But the simple natures themselves, and our apprehension of them in themselves cannot be false. To apprehend a simple nature is to judge it correctly and completely:

... if we have even the slightest grasp of it in our mind — which we surely must have, on the assumption that we are making a judgement about it — it must follow that we have complete knowledge of it. Otherwise it could not be said to be simple, but a composite made up of that which we perceive and that which we judge we are ignorant. (AT X, 420-421)

Falsity is exclusively a quality given to those complex natures constructed by the intellect, in its active attempt to constitute the world as intelligible. The units of this construction, and those natures by which that construction is intelligible, are the simple natures. In themselves, simple natures escape any notion of falsity, and thereby (somewhat paradoxically) any notion of truth.^[5] Simple natures simply are, regardless of the fact that they are the essential components of the cognitive activity which does admit the notions of truth and falsity.

By moving to the issue of judgement, we enter that aspect of intuition which only indirectly concerns simple natures: their connections. To some extent it would seem that simple natures are essentially connected. What else could intelligibility be, if not a hierarchy of valid inference relations between trans-cognitive objects? How could isolated particulates function as the core of the essentially relational process of rationality? Descartes’ treatment of simple inferences as the appropriate objects of intuition seems to confirm this. The process of enumeration is precisely intended, when perfected, to render a deduction which is sufficiently simple and clear that “we seem to intuit the whole thing at once.” (AT X, 388) Simple deduction, as the apprehended condition of a validly completed (simple) inference, is made by means of intuition. The distinction is a crucial one: “... we are supposing that the deduction is made through intuition when it is simple and transparent, but not when it is complex and involved.” (AT X, 408)

Even in the context of simple natures themselves, when distinguishing between three sorts of simple natures, he explicitly includes in the class of ‘common’ natures, all simple inferences:

... those simple natures are to be termed ‘common’ which are ascribed indifferently, now to corporeal things, now to spirits — for instance, existence, unity, duration, and the like. To this class we must also refer those common notions which are, as it were, links which connect other simple natures together, and whose self-evidence is the basis for all the rational inferences we make. (AT X, 419)

From these discussions of simple inference relations, it would seem probable that the only proper objects of intuition are simple natures. Indeed, if intuition is an essentially passive apprehension of that which constitutes judgement, then nothing ‘presents itself spontaneously’ to us other than the simple natures. Intuition is the apprehension of these objects. At the very least, therefore, simple inferences are a kind of simple nature.

The contention that all simple natures must be relational is a more difficult possibility to demonstrate. It does not help matters that Descartes himself seems to waver on this point. It should be clear that if simple natures are the core constituents of rational thought, then they are in the first place reactive.^[6] This might not be an important point to stress if the issues of conjunction did not present the Rules with so much difficulty. As he turns his attention to the connections between simple natures, essential for an adequate description of complex natures, Descartes seems to ultimately appeal to ‘a certain confusion in necessity’:

The conjunction is necessary when one of them is somehow implied (albeit confusedly) in the concept of the other so that we cannot conceive either of them distinctly if we judge them to be separate from each other. (AT X, 421)

From the dimension of method, this seems a reasonable assessment of the nature of the connections among the simple natures. As we approach a simple nature, by analysis of a complex nature, we simultaneously sharpen our focus, and isolate each simple nature from its relational context (indeed, the two operations are part of the same movement). Of course the complex of two simples will be more confused than each in isolation. This seems an obvious result of the entire project.

But more is being said here. The conjunction, where it is necessary, is integral to one of the simple natures implied in the relation. Neither of the simple natures which participate in such a relation is fully independent of it, or of each other. Contrasted with this notion is contingent conjunction. Here, it seems, the conjunction is incidental to the simple natures conjoined. This might have been an utterly trivial observation, simply tallying the logical alternative to the strict binding of simple natures into complex judgments, if Descartes had not used this distinction to reveal a more subtle feature of the relationship meant by conjunction. “Finally,” he says, “we must note that very many necessary propositions, when converted, are contingent.”(AT X, 422)

From this comment, we are forced to recognize that by conjunction Descartes often means something more like logical implication (where from PQ we cannot validly infer QP) than a strict logical conjunction (of the form P & Q). Recalling that by conjunction, he is speaking of propositions (and that propositions in this context are judgments), it is by an act of intellect that such conjunctions are confirmed. Indeed, it seems such propositional manifestations of simple natures often provide a more complete (albeit implicit) apprehension of each one.^[7] How is this possible when such connections are contained in the concept of each participant somehow confusedly? It might seem that such an essentially unclear aspect of any simple nature under examination would profoundly corrupt the precision of our final apprehension.

If we recall the notion of abstraction, in the context of focusing the intellect beyond absolute intelligibility, some sense can be given to the idea that this kind of confused implication is essential to recognizing a simple nature so conjoined. Although the notion of ‘limit’ is not more precise than those simple natures from which it is abstracted, none of those simple natures would be adequately discerned if their shared participation in the notion of ‘limit’ were not recognized. In at least this sense, the notion of ‘limit’ is confusedly implied within those simple natures which constitute it. The further act of intellect upon the bare intelligibility of shape, in addition to revealing ‘aspects’ which are necessarily diminished in clarity, must proceed along lines analogous to abstraction (or the apprehension of connections between and among various simple natures).

If these connections are imagined as being correctly represented by logical implication, as was suggested earlier by the nature of conversion, then it seems they would nicely fall under the category of simple inferences between simple natures. Because such simple inferences are themselves considered simple natures, it would then be clear that we have merely identified an additional component of a complex nature under examination. But this still does not appear to adequately capture the connectedness of those simple natures involved.

A brief look to the explicit treatment of simple natures as they are reflected from the dimension of method will reveal something of the relational aspect of them. While it is true that simple natures are construed as elemental in the propositions by which we form judgments, it would be a mistake to imagine that we come to such judgments by a kind of movement of the intellect from an apprehension of component simples, toward their conjunction in the understanding. The simple natures are logically prior to their aggregations — where logical priority is a sort of epistemic implication. But the apprehension of propositional content, and the subtle confusion which often accompanies it prior to analytic investigation, suggests that direct cognition of complex natures regularly precedes the re-cognition of their constituent natures. Simple natures are, as the intellect first apprehends them, aggregated.

The purpose of a proper method seems to be primarily interested in dismantling the activity of the intellect, such that the integrity of its judgment can be evaluated. It is not a constructive enterprise. The apprehension of simple natures, like the apprehension of points (and distances) on a number line, is only rationally interesting when it is understood as the result of a parsing operation, taken on the meaningful components of thought. Meaning, truth, validity, indeed the fabric of judgment itself, is clarified by the method, only because the simple natures revealed by the process are exhaustively constitutive of these complex operations:

... the whole of human knowledge consists uniquely in our achieving a distinct perception of how all these simple natures contribute to the composition of other things. (AT X, 427)

The apprehension of those simple objects of the intellect’s activity explicate the links between the aggregates of knowledge which come to us as the entities of empirical experience:

... it is by means of one and the same idea that we recognize in different subjects each of these familiar entities, such as extension, shape, motion, and the like,... This common idea is carried over from one subject to the other solely by means of a simple comparison, which enables us to state that the thing we are seeking is in this or that respect similar to, or identical with, or equal to, some given thing. Accordingly, in all reasoning it is only by means of comparison that we attain an exact knowledge of the truth. (AT X, 439)

Indeed, the identification of those links is the clarification of the constitutive simples. By attending to the objects of experience, we confront the aggregation of simples first as aggregates. Enumeration of those aspects of our apprehension which isolate the object, as well as those which relate it absolutely to other objects of experience, is executed by the enumeration and discernment of constituent simple natures. They are brought under the naked light of the intellect, where both the units of absolute comparison, and the steps whereby relative comparisons might be reduced to absolute ones, confront us as the core of the object’s intelligibility.

... [It would be advantageous] to think of all knowledge whatever — save knowledge obtained through simple and pure intuition of a single, solitary thing — as resulting from a comparison between two or more things. (AT X, 440)

Simple natures arrive connected. They are elicited from the propositions of judgement by isolating the basis of their connections (in the form of both similarities and differences). Once these connections stand revealed in their absolute simplicity, the bare intelligibility they carry is impressed upon us (in a condition Descartes terms intuition). The alternative reading of simple natures as essentially incommensurable, while possible given the flavor of Descartes’ insistence that clarity be accompanied by a recognition of the absolute uniqueness of each simple nature, has at least one serious drawback. If simple natures are discerned so sharply that their inferential situatedness vanishes, the analytic project has gone so far as to render absolute intelligibility unintelligible. If the intelligibility of these epistemic atoms is to be maintained, then the condition of uniqueness can only be understood as existing in terms of a wider notion of interconnectedness. Otherwise, it is hard to see how they could be constitutive of anything.