ONE
The Internal Senses and Descartes's Psychophysiology of Imagination

In the introduction I mentioned Descartes's indebtedness to a tradition of philosophical psychology that placed so-called internal or inward senses between the five external senses and the powers of intellect. The purpose of this chapter is twofold: (1) to introduce the chief elements of the doctrine of the internal senses and situate the imagination within it and (2) to demonstrate the connection of the psychology and physiology of understanding elaborated in Descartes's Regulae ad directionem ingenii to this tradition. As we shall presently see, although at first glance the psychophysi-ology of the Regulae reads like an anticipation of the later theory of the pineal gland (as the seat of the soul in the body), it is in a more original sense an outgrowth of the doctrine of internal senses.

A. IMAGINATION AND THE INTERNAL SENSES BEFORE DESCARTES

Imagination is a name traditionally given to one of the powers of the mind enumerated in so-called faculty psychologies,^[1] which divide the human soul according to fundamental capacities. Most medieval discussions follow Aristotle in taking the vegetative, sensitive, and intellectual parts as

[1] As pointed out by Jerry A. Fodor, although faculty psychology is pronounced dead in every century, it invariably recovers; see Fodor, The Modularity of Mind: An Essay on Faculty Psychology (Cambridge: MIT Press, 1983). The central issue for a psychology of faculties is not whether mind or soul is thought to have various functions but the degree of independence of these functions from higher powers. For example, if the senses are thought to operate in essential independence from intellect, then sensibility is an independent faculty; intellect, in its turn, might function independently of sense, for instance insofar as it does not require the immediate action of the senses. As soon as one allows even a small degree of independence to a function, one has in fact taken the first step into a psychology of faculties.

basic; Thomas Aquinas amplifies this to five by adding the appetitive (including will) and the locomotive powers.^[2] Each of these parts may in turn be subdivided according to its various functions and objects. The intellectual power, for instance, can be divided, according to its mode of operation, into intellect, which is immediately apprehensive, and discursive reason, which proceeds by stages; or, emphasizing instead the object toward which the faculty is directed, one can divide it into the three capacities of knowing (l) what is changing, (2) what is unchanging but material, and (3) what is unchanging and wholly immaterial.

The sensitive powers include not just the five external senses of sight, hearing, touch, smell, and taste but also the internal senses. Although there was no little disagreement about the precise number of the internal senses, their proper names, their organic locations, and the correct delimitation of their functions, there was sufficient consistency in medieval presentations for us to abstract a core theory. The core theory ultimately derives from Aristotle but has admixtures from other philosophical traditions and incorporates scientific and medical doctrine as well.

In a first approximation we should note that the sensitive powers, which human beings share with other animals, are intermediate between the vegetative-nutritive-reproductive powers possessed by all living things and the intellectual powers possessed (at least among physical beings) only by humans. In contrast to the vegetative powers, the sensitive powers involve an awareness of things, or at least of aspects of things. Awareness does not make them intellectual, for the intellectual powers proper operate at the level of abstractions, universal concepts, and generalizations, whereas the sensitive powers deal with sensory aspects of singular things. Still, there can be more than a superficial resemblance to understanding in animal sensibility. This is evident not so much from individual sensations—seeing a color, hearing a tone, smelling an aroma—as from the ability of animals to use multiple sensations of the same and different types, to compare and remember them, in order to survive and prosper. So, for example, most mammals learn from a small number of incidents to avoid situations that produce unpleasant effects, and they can make discriminations in their environment that permit them to secure food and shelter and to raise their young. Although some might be inclined to call these abilities forms of intelligence and to treat them as in essence intellectual, the tradition I am describing saw these as closer to the external senses than to intellect. Nevertheless, they opened the way to the conception of a deeper kind of sensibility that is crystallized in the internal sense tradition.

As I have already noted, the ultimate source of the internal senses doc-

[2] Summa theologiae, 1, q. 78, art. 1.

trine is Aristotle's psychological writings, especially De anima (On the Soul). The second and third books of De anima develop a theory (beyond the vegetative) of the sensitive and cognitive powers of soul: the five external senses, the common sense (aisthesis koine ), imagination (phantasia ), receptive intellect (nous pathetikos ), and agent or productive intellect (nous poietikos ). This cognitive psychology was predicated on the existence of forms in substances (for our purposes 'substance' can be taken to mean physical objects, though for Aristotle there are immaterial substances, too): an essential form, which constitutes the nature of the thing and makes it the kind or species of thing it is (e.g., the form of human being), and sensible forms, which determine the various (many nonessential) sensible qualities of the thing (e.g., the visible form/shape of a particular human body).^[3] Sensible forms can be communicated to the properly disposed sense organs of animals, and they are divided into two kinds: proper sensibles, those things that are perceived by one and only one sense (color in vision, odor in smell, sound in hearing, etc.), and common sensibles, like movement, rest, figure, magnitude, number, and unity, which are communicated to more than one sense (e.g., both the eye and touch can detect figure).

It must not be thought that this communication of forms necessarily occurs through local motion or that it takes time, say by means of an "Aristotelian photon" flying through space from object to sense. Aristotle does not, for example, conceive of vision as being due to the transmission of little objects or impulses. Rather, a proper sensible in the object, for example its color, acts on the organ when the medium between them, in the case of color what Aristotle calls the diaphanous or transparent, is made actually transparent by light. In darkness, transparent materials are only potentially diaphanous, and so colors cannot be communicated to the eye; but light activates the medium, thus enabling it to be the means through which the sensible form communicates itself to the sense organ.^[4] The result is that the sense receives into itself the sensible forms of things without the matter.

To use the classic formula, the sense in act is the sensible object in act; that is, the sense of sight as it is actually engaged in seeing is the same as the activity of the sensible form of the object (which is communicated

[3] An argument might be made that this division into essential and sensible forms is artificial, that it is from the essential form that the act of an object is communicated to the sense organs, which receive and differentiate the form according to their natures. But the evidence of Aristotle's text justifies locating sensible forms in the object.

[4] Once again, this is not like the case of light rays bouncing off an object and traveling to the eye, because in such a case the light rays, not the diaphanous, would be the medium. A further step away from the Aristotelian conception would be to consider the rays not as a medium but as makers or stimulators of color (the early modern scientific notion of color as understood by Galileo, Descartes, and Newton).

through the medium without the matter of the object and activates the sense organ). Or to use the image that anticipated Descartes's use of it (in Rule 12, AT X 412) by nearly two thousand years, "every sense is receptive of the forms of sensible objects without their matter, and in a sort of way in which wax receives the impression of a signet-ring without the iron or gold, for the wax receives the impression of the golden or bronze [ring] not qua gold or qua bronze" (424a17-2l; brackets in source).^[5]

Between his discussions of the five senses and intellect, Aristotle introduces two other powers that, with the addition of memory, initiated the internal senses tradition. The first is common sense, so named because it is that part of sense in which the common sensibles like motion and shape are perceived. The eye receives not just color but also motion, rest, number, shape, and magnitude (418a18-20) but itself perceives only what is proper to it, color. Another power is therefore needed in which the common sensibles can be perceived alongside the proper sensibles and in which the sensibles from all the different sense organs are brought together into a unified field of perception.^[6] The eye judges of redness, but the unified sense, not the eye, judges that a red thing is moving, that it is round, that it is large, and so on. Vision by itself recognizes not objects as such but colors; hearing recognizes not things but sounds; and similarly for the other external senses. But to recognize that this white, crystalline stuff, called sugar, is sweet, to recognize that an assemblage of colors is a thing, and to recognize that a particular object has such-and-such characteristics is perceived not by any individual sense organ but in the common sense.

The justification for this faculty is perhaps clearest from the need to coordinate and compare the information^[7] of the different senses. We can not only see with our eyes but also feel by our touch that a thing is moving, round, or large, and these two "channels" of information are perceived as referring to a single thing. Neither the eye nor the tongue is able to judge that the white stuff we call sugar is sweet (the eye perceives whiteness but not sweetness, the tongue sweetness but not whiteness). The common sense is able to do these things because it is where the different sensibles are unified.

The common sense, we might conclude, is the repository of the unified image of sensation. But we also have images when we are not directly sensing things, and this justifies introducing another sensitive power preced-

[5] Translations from De anima are taken from Aristotle's "On the Soul" (De anima), trans. Hippocrates G. Apostle (Grinnell, Iowa: Peripatetic Press, 1981).

[6] 'Unified field of perception' is not Aristotle's term, but it gives some sense of the problem being addressed.

[7] It is not entirely illegitimate to think of both the modern and the Aristotelian connotations of this word.

ing intellect, phantasia or imagination. There is debate about whether imagination is really a faculty for Aristotle,^[8] but we can by and large ignore this, since for the vast majority of Arabic and Latin commentators there was no doubt that it was a faculty—which is not to say that they thought there were no difficulties of interpretation. Difficulties arise not least because Aristotle's discussion of imagination is dialectical and problematical.

Most of the third chapter of book 3 of De anima (cited below as De anima III 3) is devoted to distinguishing imagination from external sense, common sense, opinion, belief, knowledge, and intellect, with due regard given to possible connections to these. Put summarily, Aristotle argues that if imagination, the power or habit by virtue of which images are formed in us, is a power of discrimination, it is nevertheless different from other discriminating powers, like the external senses and common sense, because it does not require the presence of an object, although it does depend on the previous activity of these (i.e., if one has never sensed anything, one cannot have images). Because imaginings are not inherently true, imagination must also be differentiated from the cognitive faculties that are always true, like knowledge and intellection. It is not identical with or a variety of opinion, nor is it a mixture of opinion and sensation, because conviction and reason always accompany opinion, whereas neither is necessary for imagining. He concludes that imagination has not so much to do with the proper activities of the senses—which are infallible with respect to the proper sensibles (when the eye sees red it is really seeing red)—as with the attribution of proper sensibles to objects and the discrimination of common sensibles, which are sometimes false. "Accordingly, if no thing other than imagination has the things stated above, then imagination would be a motion produced by the activity of sense" (428b30-429a2). "And because imaginations persist in us and are similar to the corresponding sensations, animals do many things according to them, some (i.e., non-rational animals) because they possess no intellect, and others (i.e., men) because their intellect is sometimes clouded by passion or disease or sleep" (429a4-8). Like the external senses and the common sense, imagination is of the sensible; but its objects need not be immediately present, and it is responsible for or related to the persistence and the repeatability of images.

This account of De anima III 3 leaves many questions unresolved. It is not entirely clear, for example, what it means for imagination to be a

[8] See Michael V. Wedin, Mind and Imagination in Aristotle (New Haven: Yale University Press, 1988); Malcolm Schofield, "Aristotle on the Imagination," in Essays on Aristotle's "De Anima," ed. Martha C. Nussbaum and Amélie Oksenberg Rorty (Oxford: Clarendon Press, 1992), 249-277; and Dorothea Frede, "The Cognitive Role of Phantasia in Aristotle," also in Essays on Aristotle's "De Anima," 279-295.

motion produced by the activity of sense. Since images persist in imagination, it would seem to have some significant relationship to memory, although that is not pursued in De anima,^[9] and it appears to overlap the common sense in that it deals in matters of the unified sense (one would assume with different functions). The obscurities and unresolved questions would by themselves have occasioned at least some elaboration from commentators. But the deepest reason for the persistence of interest in Aristotle's doctrine of phantasia was a claim made in De anima III 7 that puts imagination at the heart of knowing itself.

Images are to the thinking soul like sense impressions. But when [the thinking soul] affirms or denies them as good or bad, it pursues or avoids, respectively, and for this reason the soul never thinks without images. . . . The thinking part, then, thinks the forms in the images; and just as what is to be pursued and what is to be avoided [when the sensible objects are present] is determined for it by the corresponding [sensations], so it is moved when images are before it and there is no sensation. For example, sensing a beacon as being fire, it knows by the common faculty of sensation that the enemy is approaching when it sees the beacon in motion. At other times, it forms judgments and deliberates about future objects relative to present objects by means of images or thoughts as if it were seeing these objects; and whenever it asserts that [certain objects imagined] are pleasurable or painful, it pursues or avoids [those objects] as it does when it senses objects; and it does so in actions in general. (431a14-17, 431b2-10; brackets in source)

There is no thinking without images, without phantasms. The word for thinking here is dianoein, which in Aristotle implies judgment, the discursive thinking that combines or divides two things; in De memoria et reminiscentia the same statement is made of noein, which embraces both discursive thinking and the intuitive grasp of simple things (terms or concepts, the elements that discursive thinking combines in judgments).^[10] Aristotle's

[9] But rather in De memoria et reminiscentia; see Richard Sorabji, Aristotle on Memory (Providence: Brown University Press, 1972).

[10] Noein, corresponding to nous, would refer specifically to any simple act of receiving a fundamental concept or principle; more generally, it comprises both the intuition of simple concepts and the combination of them in judgments. The passage from De memoria et reminiscentia (450a1-6) reads:<HR>

An account has already been given of imagination in the discussion of the soul, and it is not possible to think without a phantasm. For the same affection occurs in thinking as in the drawing of a diagram. In the latter case, even though we are not also using the triangle's being determinate in quantity, nonetheless we draw it determinately as to quantity. In just the same way, the person thinking, even if he is not thinking of quantity, places [a] quantity before his eyes, but does not think of it qua quantity. Even if the nature [of what he is thinking] is among the quantities, but indeterminate, he places before him a determinate quantity, but thinks of it qua quantity only. (Quoted after Lachterman, The Ethics of Geometry, 82)

formulations in terms of good/bad, pleasurable/painful, and future acts might lead one to suspect that the dictum applies to practical activity and not to theoretical. But in the same passage of De anima he notes that "objects which are outside of the sphere of action, too, i.e., the true and the false, come under the same genus, namely, that of good and evil; they differ, however, [by being good or evil] either without qualification or in a qualified way" (431b10-12; brackets in the source). What the original statement means, then, is that all discursive thinking—all thinking of any kind, if we take into account the passage from De memoria et reminiscentia —requires phantasms, and images are important not just because they are fundamental to the activity of comparison that underlies judgment but also because it is from images that the form or essence of a thing is arrived at, is abstracted. Moreover, chapter 7 leaves open the question of whether it is even possible for the intellect to think an object separate from matter.^[11] The image, with its remnants of corporeal magnitude, is at the core of Aristotle's ontologically grounded epistemology.

Chapter 7 of book 3 corrects an impression that one can easily get: that the treatment of phantasia in chapter 3 was included for the sake of completeness rather than intrinsic importance, since chapters 4 and 5, which treat the crucial topics of receptive and agent intellect, make no reference to images. But those latter two chapters are dedicated chiefly to continuing the differentiation of soul powers from one another that began in book 2. Accordingly, they identify the factors that differentiate intellect from other parts of the soul and distinguish the intellect according to its activity (agent intellect) and potentiality (receptive intellect).^[12] It is only in the following chapters, and there quite briefly, that Aristotle discusses the interrelations of the sensitive and cognitive powers in human knowing and doing.

Understanding the nature of the twofold intellect was one of the chief and most controverted parts of Aristotle's De anima for the Middle Ages. This was not just because of the importance of the question of knowing but also because it bore on the immortality of the soul and its relation to

[11] "In general, then, the intellect when in actuality is the objects which it thinks. But whether the intellect, which is not separate from magnitude, can or cannot think any separate object is a matter to be considered later" (De anima, 431b17-19). The question is not treated subsequently in De anima; one might consider the discussion of thought thinking itself in the twelfth book of Metaphysics as decisive, but even there the question might be raised whether human beings can truly think what is separated from matter.

[12] Intellection is not simply an automatic process set off by lower parts of the soul. For Aristotle, everything that is not unchanging needs to be understood in terms of potentiality and actuality, and since human intellect is sometimes understanding and sometimes not (or sometimes understanding one thing, sometimes another), there must be a cause of this change from one to the other state. Chapters 4 and 5 of book 3 show that in intellection cause and effect are ontologically correlative.

God, inasmuch as Aristotle had stated that although all the other faculties pass away with the animal body, the agent intellect is apparently separate and unchanging. In what follows I shall by and large leave untouched the questions of immortality and of whether the agent intellect is part of the human soul or instead a divine emanation (as in Avicenna) or even God himself. My focus will be the interpretation of the process of cognition.

Rather than continue here with an analysis of Aristotle himself, we can now turn to Avicenna's interpretation of imagination in the process of knowing, since his theory of the former as one of the internal senses became canonical for the later Latin thinkers. Avicenna^[13] (980-l037) was a Persian philosopher and physician whose medical writings were probably the single most important influence on the medicine taught in European universities through the Renaissance and whose commentaries on and elaborations of Aristotle (along with those of Ibn-Rushd, or Averroës, 1126-1198) decisively shaped the reception of the Peripatetic philosophy in the thirteenth-century West. Indeed, it is likely that at the beginning of that century Avicenna was better known and more influential in the Occident than was Aristotle.^[14] In his own work about the soul, also titled De anima, he tried not only to present Aristotle's teachings but also to clarify and develop what the Greek philosopher and his commentators had left obscure or implicit. In so doing, Avicenna contributed new doctrines and theories that were to shape the later medieval and Renaissance conceptions of the soul and its cognitive powers.

In his De anima, Avicenna identified five internal senses. They were translated into Latin under the names (1) fantasia or sensus communis, (2) imaginatio, (3) vis aestimationis, (4) vis memorialis or reminiscibilis, and (5) vis imaginativa or cogitans.^[15] The phantasy or common sense is basically the common

[13] This is the familiar Latin form of his name; the Arabic is Ibn Sina^[*] .

[14] See John Marenbon, Later Medieval Philosophy (1150-1350): An Introduction (London: Routledge & Kegan Paul, 1987), 50-65, esp. 54-55.

[15] See Marenbon, Later Medieval Philosophy, 105-106; see also E. Ruth Harvey, The Inward Wits (London: Warburg Institute, 1975), 40-41. Avicenna's De anima was translated into Latin in the twelfth century by Gundissalinus. The Latin tradition quickly abandoned the terminological identification of 'phantasia' with 'sensus communis' found in the translation of Avicenna. 'Phantasia' and 'imaginatio' were rarely used by any single thinker as direct synonyms; it was common to find them (or cognates) used to distinguish internal sense powers, for example the store of available sense images versus the power to combine, divide, and recombine images. The Latin terminology, at any rate, varied greatly from author to author. For discussions of the tradition of the psychology and anatomy of the internal senses, see Walther Sudhoff, "Die Lehre von den Hirnventrikeln in textlicher und graphischer Tradition des Altertums und Mittelalters," Archiv für Geschichte der Medizon 7 (1913): 149-205; Edwin Clark and Kenneth Dewhurst, An Illustrated History of Brain Function (Berkeley, Los Angeles, and London: University of California Press, 1972), esp. 5-55; Harvey, The Inward Wits ; Nicholas Hans Steneck, "The Problem of the Internal Senses in the Fourteenth Century," Ph.D. diss., University of Wisconsin, 1970; Harry Austryn Wolfson, "The Internal Senses in Latin, Arabic, and Hebrew Philosophic Texts," Harvard Theological Review 28 (1935): 69-133; Marenbon, Later Medieval Philosophy ; Katharine Park, "The Organic Soul," in The Cambridge History of Renaissance Philosophy, ed. Charles B. Schmitt and Quentin Skinner (Cambridge: Cambridge University Press, 1988), 464-484; and David Summers, The Judgment of Sense: Renaissance Naturalism and the Rise of Aesthetics (Cambridge: Cambridge University Press, 1987).

sense of Aristotle: it is the place where all the sensible forms are perceived. These forms are stored for future use in the imagination, a kind of sense-image memory. Besides the forms that can be sensed, there are also instinctive perceptions or judgments of good and bad, advantageous and harmful (like a young, inexperienced lamb's recognition of the danger posed by a wolf); these so-called intentiones, or intentions, are received in the vis aestimationis, or power of estimation. The memorial or reminiscible power stores these nonsensible intentions, just as the imagination stores the sensible forms that have been received by the common sense. The remaining power is called vis imaginativa in animals, vis cogitans in the human being. This power, as one scholar describes it,

compounds and divides (componere et dividere) both sensible forms taken from the imaginatio and intentiones taken from the vis memorialis.Beginning with one of them, it proceeds by nature to another which is contrary or similar or in some way to be compared to the first. . . . As the name Avicenna chooses for it in humans indicates, the vis cogitans engages in discursive thought; but the cause of its movement from one image or intention to another is always a singular thing, not a universal.^[16]

The cogitative power is thus based on our ability (and, in some sense, also the ability of animals) to see one imagined sensible form in relation to another or in relation to the intentions, which in animals embody an instinct for good and bad.

Avicenna's theory of the internal senses explains the progressive dematerialization or abstraction that takes place in the processes of sensation and intellection. As the form, image, or phantasm is passed on from sense organ to common sense to imagination, and so on, it undergoes a progressive elimination of the particularities of the original object. The theory is also in large part physiological; that is, the internal senses are dependent on and localizable in the body. Physicians in antiquity had already suggested the localization of the sensitive and rational powers, and Avicenna's extension of this does not seem to be inconsistent with Aristotle's intentions. In the Canon of Medicine, translated into Latin in the twelfth century by Gerard of Cremona, Avicenna first divides the so-called animal virtue into the comprehensive and the active virtues; the former includes both external and internal senses. The Canon points out that the internal senses

[16] Marenbon, 105-106.

are considered by doctors to be three in number: phantasia in the anterior brain ventricle, virtus cogitativa in the middle, and virtus memorialis or conservativa in the posterior. Philosophers make more precise distinctions and identify five: the front ventricle has sensus communis to receive sensations and phantasia to retain them; the middle ventricle's virtus cogitativa is referred to as 'imaginativa' when it is under the command of extimativa animalis and 'cogitativa' when the rational power makes use of it. The virtus extimativa does not properly have a ventricle, although its functioning depends on the other internal sense powers.^[17] Both human beings and animals have this instinctive attribution of good and bad, safe and dangerous. This power is not, however, to be confused with the higher powers proper. "The comprehending power, which is one of the comprehending powers of the soul, is the human reason. And because doctors do not deal with the estimative power for the reason we have given, they do not deal with this power for the same reason: it works only through the other three powers [that the doctors identify], and not in other things."^[18] The last power, virtus memorialis/conservativa, is the same for philosopher and doctor. In addition to this psychophysiology of the internal senses, Avicenna also held to the traditional Stoic medical doctrine of animal or bodily spirits, which were considered to be "the bearer of the powers of the soul in the limbs of animals, which work by [their] means."^[19]

Avicenna was not unique in making the powers of the internal senses the focal point for a cooperation of body and soul that extended, on the one hand, into the movements of the body and, on the other, into the realm of reason, nor was he the first to do this, but he was the most influential, especially in the West. The psychophysiology of the internal senses became a commonplace, although the exact names of the powers, the discrimination of their functions, and their degree of independence from intellect varied from author to author. A particularly important example is Aquinas, who followed Avicenna quite closely (except for the names) in the cases of sensus communis, imaginatio (for fantasia), and vis memorativa. He criticized Avicenna's conception of imaginativa/cogitativa (which Aquinas gave the alternative name 'fantasia'), however. This is the power that combines and divides imaginary forms like the golden mountain. Aquinas did not deny the existence of the power but rather ascribed it (following Averroës) to the imagination. Moreover, Aquinas's vis aestimativa is to be distinguished from Avicenna's virtus extimativa. In the Canon

[17] In the De anima, he nevertheless positions the estimative power at the top of the middle ventricle; see Harvey, The Inward Wits, 45.

[18] Quoted by Harvey, The Inward Wits, 24; the bracketed interpolation is mine. The discussion of this paragraph is largely adapted from Harvey.

[19] Quoted by Harvey, The Inward Wits, 24; the bracketed interpolation is mine.

Avicenna had described it as depending on the other internal powers but as not properly located in any of the brain ventricles; in the De anima, however, the vis extimativa was considered to be in the middle ventricle and closely related in function to imaginativa, cogitativa, and memorialis (especially to the former two, since they also were seated in the middle ventricle). For Aquinas, the aestimativa, which in animals is the most judg-mentlike of the internal senses, is in human beings called cogitativa or ratio particularis. It is the sensitive power that is most deeply touched by the rationality of human nature. It is the power by which the human being knows individuals as falling under a universal, although only intellect can know the universal as such. One modern analysis of the cogitativa in Aquinas explains it this way:

Does therefore the cogitative, a sensible and organic faculty, know the common nature, that is, man or oak as universal? St. Thomas is careful to say no such thing. He says that the cogitative knows the individual as existing, and as coming under the human nature. Strictly speaking, therefore, it knows only the individual. Yet, the human being who makes use of his cogitative sense becomes conscious—a thing that the brute beast could never do—that this object-individual which he apprehends by his cogitative realizes the universal nature of man or of oak, and he knows this universal nature of man or of oak by his intellect.^[20]

Granted that there is already a kind of thought that is at least implicit in the highest internal senses: how does intellect use the phantasm prepared by them to think in the full sense? The answers to this question in the Arabic and Latin Middle Ages were manifold. Avicenna had agent intellect strip the image of its last vestiges of matter and accidents, but this stripped image was not itself impressed in receptive or passive intellect (what Aristotle had called 'nous pathetikos'); rather, the passive intellect was thereby made ready for the intelligible form that came from agent intellect itself. This agent intellect, the last of the emanations of God, was separate from all human souls; as the common source of intelligibility, it explained how different people could be said to understand the same thing in the same way. This problem of the sameness of understanding in different actors and acts of understanding was of even more crucial importance to Averroës, who did not accept Avicenna's estimative power as a special faculty. He believed that the ancients had attributed the functions of estimation (receiving nonsensible intentions) to the imaginative power, and he numbered the "immaterial faculties" that Aristotle had posited as four: common sense, imagination, cogitation, and memory. But in some

[20] Julien Peghaire, "A Forgotten Sense, the Cogitative according to St Thomas Aquinas," Modern Schoolman 20 (1943): 121-140, 210-229; see p. 140.

contexts Averroës reduced the number to three, the imaginative, the cogitative, and the memorative, one for each of the three ventricles of the brain that he identified.

For both Avicenna and Averroës, the imagination is very close to the highest power that human beings possess per se. In Avicenna nous poiet-ikos, or agent intellect, does not properly belong to human beings, although passive intellect (nous pathetikos) does; but there is at least a partial identification in Avicenna of passive intellect with imagination (e.g., in the Kitab al-Najat, he calls imagination a second passive intellect).^[21] For Averroës, imagination, that is, the power of dividing and composing images (which he also sometimes referred to as cogitation), was quite simply the highest power of man; both the passive and the agent intellect were from God and could be participated in by man only in the presence of a properly disposed phantasm.

All five (or four, or three) of the internal senses are involved in the preparation of phantasms, and one of them, the cogitative or its equivalent under some other name, even "thinks" those phantasms according to a particular form. For the future history of the theory of the internal senses, in particular for Descartes's conception of the function of imagination, Avicenna's teaching is crucial, especially in that it was transmitted with essential integrity to the Latin High Middle Ages by Albert the Great.^[22] But Averroës's scheme had its proponents as well, one of them no less influential than Aquinas. Despite the many variations that arose (especially in the use of terminology), its basics, its "topography" of organically located internal senses that effect the common field of sensation, the retention of images and reactions to images, the recall of them, and their composition and division, remained canonical right up to the beginning of the early modern period in Europe. The internal senses were understood as multiple, as corporeal, and as to some degree already involving, or at least imitating, thought, and the imaginative functions were conceived as closely connected with, even identical to, the cogitation of particulars.

In the tradition of internal senses, external sensations are not immediately taken up by the intellectual powers but rather "processed" at an intermediate level. Although any animate being is able to make very simple discriminations at the level of sensation—vision, not an internal sense or intellect, distinguishes black from white and red from blue—more sophisticated distinctions require a higher faculty (common sense first of all, which distinguishes color from depth from aroma). These distinctions are

[21] See F. Rahman, Avicenna's Psychology (London: Geoffrey Cumberlege, for Oxford University Press, 1952), 68-69, 115-116. Already in antiquity commentators like Simplicius had identified imagination with passive intellect.

[22] See Steneck, "Problem of the Internal Senses in the Fourteenth Century," esp. chaps. 1-3.

not yet intellectual, however: just as there is an awareness at the level of vision, there is another awareness at the level of each internal sense.^[23] The internal senses as a group are capable not just of registering images delivered by the external senses but also of comparing, contrasting, decomposing, and recomposing them and (since it is of the essence of performing discrimination and comparison) of seeing one image in relation (identity and difference) to others. This capacity of relating images to one another is what allows the internal senses at their peak to exercise the power of particular judgment. Furthermore, since the internal senses are sensitive powers, they have organs or organic location just as the external senses do. The medieval thinkers, supported by both medical and philosophical tradition, assigned them to the interior spaces of the brain, the ventricles enclosed by the two hemispheres. Throughout the medieval and early modern periods one finds illustrations and diagrams of the positions of the internal senses in the head; it was customary, for example, to place the common sense in one of the front or anterior ventricles, the recombinative power of imagination or cogitation in the middle ventricle, and the memory in the posterior ventricle. The medieval writers were quite aware, therefore, that anatomical and physiological differences between individuals could affect the operations of the internal senses. Moreover, since a phantasm is required for thinking proper and the phantasm is prepared by the internal senses, lesions or diseases could impair a person's ability to think and understand. In short, the constitution of the internal senses could particularize, even personalize, the powers of experiencing and knowing that are common to all human beings.

Although I have discussed the internal senses as part of Aristotelian tradition, it is important to realize that the basics of the doctrine were accepted even by those who were not properly Aristotelian or Scholastic. Quite apart from the fact that medical knowledge appeared to support it, the doctrine had analogues in other philosophical traditions, especially the Platonic and the Stoic. Accepting some version of the internal senses was thus no more controversial in late medieval and early modern Europe than it would be today to hold that different parts of the brain are responsible for different motor, speech, and cognitive functions (indeed, one can trace a line from the psychophysiology of the internal senses down to modern theories of brain function).^[24] The medical tradition also helped contribute to a synthesis of Aristotelian themes with the Stoic conception of

[23] This parceling out of awareness is not at all counterintuitive. An assembly line worker might be able to sort parts by color while daydreaming, and a driver might be able to negotiate traffic all the while she is considering a mathematical proof.

[24] As is done in Jean-Pierre Ghangeux, Neuronal Man: The Biology of Mind, trans. Dr. Laurence Garey (Oxford: Oxford University Press, 1985), and in Clarke and Dewhurst, Illustrated History of Brain Function.

imagination and psychophysiological functions. The Stoics believed that the nerves were hollow tubes filled with pneuma, a very fine, active matter capable of moving and animating grosser matter. These spirits, as they came to be called, were conceived as the means by which the impressions of the senses were conveyed to the command center of the brain, the hegemonikon , and it was also by means of these spirits that thinking could command the body. The Stoic pneuma doctrine ultimately became embedded in the psychophysiology of the internal senses. In particular, spirits were thought to fill the ventricles of the brain; although by today's standards there was insufficient attention to the details of the role they played in internal sensation, there was little doubt that they did.

I have mentioned the Stoics not simply because they contributed a theory of animal spirits to the psychophysiology of internal sensation or because, as we shall see in what succeeds, hollow nerves filled with spirits are part of Descartes's neurophysiology. The Stoics were also responsible, it appears, for the articulation of a conceptual structure and terminology that dramatically raised the status of imagination, a structure that was conveyed to the Latin West by way of medieval Islamic and Jewish thinkers. In Thomas Aquinas and other high medieval Latin writers, one finds 'imagi-natio' used in the sense of pure conceptual intuition, of a purely intellectual imagination. This usage can be traced to a small number of conceptual pairings that came down to Arabs and Persians from Stoic writings but were used to articulate the essentially Aristotelian distinction between simple intellectual apprehension (nous, intellectus ) and discursive rational thought (dianoia, ratio ).^[25] This might seem at first only to add to the confusion about the proper meaning and status of 'imaginatio', which even in the narrower confines of the Scholastic tradition was rendered by an unsteady vocabulary often used in quite different senses by thinkers close to one another in time and place. But the variety and even the confusion may testify instead to the nature and importance of the image. The various sensory and mental capacities for producing, reproducing, and considering images are relevant to the entire range of mental experience, from conceiving, storing, and recovering ordinary sense images, through recombining them and bringing them into judgmentlike relations to one another, to understanding anything whatsoever that appears to the mind. This range of powers and problems crystallized into a network arranged about the terms 'imaginatio', 'phantasia', 'imaginativa', a network that was not in need of any single philosophical, scientific, or medical tradition to be exploited, adapted, cultivated, and, ultimately, handed down. The prob-

[25] See Harry Austryn Wolfson, "The Terms tasawwur^[*] and tasdiq^[*] in Arabic Philosophy and Their Greek, Latin and Hebrew Equivalents," Moslem World (1943) : 114-128.

lematic of the internal senses, in particular of the imagination, thus took on a relatively autonomous cultural existence.

Although we have very little specific information about how Descartes became aware of the problematic of imagination and the internal senses, its pervasiveness makes establishing any specific connection moot. That Descartes was exposed to it at school is a near-certainty. We should recall that the three-year-long philosophy curriculum of the Jesuit Henry IV College at La Flèche, which Descartes attended from around 1607 to 1615, focused on the works of Aristotle and Thomas Aquinas.^[26] Moreover, the Jesuits were the supreme cultural gatherers of their day, collecting arti-facts, information, and knowledge in their ambition to evangelize and to magnify the glory of God. We know that the precocious René Descartes was permitted to read more widely than his fellow students; doubtless he encountered imagination and the internal senses in many books and many different contexts.

We shall examine several of these contexts in the chapters that follow, ranging from the mathematical to the spiritual. For now it will be enough to mention a single work that likely was available at La Flèche and that reflects the Jesuits' conception of the philosophical and cognitive relevance of imagination. I am referring to the commentary on Aristotle's De anima prepared by Jesuit scholars at the University of Coimbra (in present-day Portugal), one of the so-called Coimbran Commentaries. The De anima commentary presents the Greek text and a Latin translation on facing pages; these texts are surrounded by footnoted comment and discussion ranging from the philological to the philosophical; and after each major section of text and comment, the format is interrupted by quaestiones that discuss the fundamental theses and conflicting interpretations pro and contra (i.e., that reflect the basic structure of the Scholastic quaestio ). One of these, the eighth question focusing on the first half of the third book of De anima, asks whether phantasms (and thus the power of imagination) are truly required for all intellectual activity. After a prolonged discussion

[26] On the years of Descartes's attendance, see Geneviève Rodis-Lewis, 'Descartes' Life and the Development of His Philosophy," in The Cambridge Companion to Descartes, ed. John Cottingham (Cambridge: Cambridge University Press, 1992), 21-57, esp. p. 23. On education at La Flèche, see Camille de Rochemonteix, Un Collège de Jésuites aux XVII et XVIII siècles: Le Collège Henri IV de La Flèche, 4 vols. (Le Mans: Leguicheux, 1889), esp. vol. 4. The Ratio studiorum, which governed education at Jesuit schools, does not mention the teaching of Aristotle's De anima, but psychological topics are included in two books which were taught, the Metaphysics and the Niwmachean Ethics, and the Catholic doctrine of separate substances would be scarcely intelligible without distinguishing the knowing processes of human beings, who require phantasms for knowing, from angelic and divine knowing. The internal senses are mentioned in a collection of theses submitted by a student in 162c; see Rochemonteix, Un Collège de Jésuites, 4:352.

the editors conclude that phantasms are necessary for ali "ordinary and common" matters. The exceptions are revealing: Christ could understand apart from phantasms because he had a divine as well as a human nature; in the afterlife, when human souls will be joined to glorified bodies, it will be possible to know intellectual things directly (although in the glorified state it will also be possible to think by way of phantasms); and, in the present life on earth, the very few who are given a special grace from God that raises them to a rapturous, ecstatic contemplation of his essence think and know without phantasms. But "ordinary" human ecstasy, like that experienced by Socrates when he stood in rapt contemplation of the Ideas for a whole day and night (told by Alcibiades in the Symposium ), requires phantasms, as do all other activities of thinking and knowing that human beings perform in accordance with their natures.^[27]

The exceptions are therefore hardly exceptions; for all practical and theoretical purposes, apart from situations in which the human being passes beyond the natural into the supernatural realm, there can be no thinking and knowing without the internal senses and their phantasms. All reasoning, conceiving, understanding, all science and truth, must come to us by way of and accompanied by phantasms.

B. THE PSYCHOPHYSIOLOGY OF THE REGULAE (RULE 12)

Having remarked these things, we are ready to commence our exploration of imagination and the internal senses in Descartes.

Anyone familiar only with the Descartes of standard interpretations is likely to find a close reading of the Regulae ad directionem ingenii surprising, since there the power of imagination is given a central role in knowing scientifically. The full extent of the importance of imagination in the Regulae will be the focus of Part II of this work. To gain a provisional sense of its role, it is useful to look at a passage from the twelfth rule that presents Descartes's early psychophysiological theory of human cognition.

Although there are controversies about the dates of composition of the Regulae —some think Descartes worked on it for about a decade, beginning as early as 1618 (when he was twenty-two years old) and ending around 1628, hereas others think that the entire work was produced in a short period ending at the latter date—it is believed that by the time he began the investigations of Le Monde (perhaps in late 1629 or early 1630) he had abandoned the Regulae. Virtually all students of the question would agree

[27] I have used the third edition: Commentarii Collegii Conimbricensis Societatis lesu, in tres li-bros De anima, Aristotelis Stagiritae, 3d ed. (Lyon: Horace Cardon, 1604); see question 8, 452-459. The first edition appeared in 1598.

that Rule 12, which discusses the psychophysiology of knowledge, was written shortly before that abandonment. Thus, if we place the beginning of Descartes's postgraduate intellectual career in 1618 (thus more or less taking the Discourse on the Method at its word), the Regulae's psychophysiology falls roughly midway between this beginning and Descartes's first publication, the Discourse and its accompanying scientific essays (1637).

Early in Rule 12, which is by far the longest of the twenty-one extant rules,^[28] Descartes presents a theory of sensation, imagination, and understanding that has obvious connections to the doctrine of internal senses, which it adapts in a novel way to a new scientific sensibility. The rule explains that impressions received by the sense organs are passed on to the sensus communis, or common sense, from where they are further transmitted to the phantasia, or imagination, which he calls "a true part of the body . . . of such magnitude that its different parts can take on many distinct figures one after another and usually retain these for a long time" (AT X 414); from this phantasia the knowing force (vis cognoscens ) can then receive an impression, or, reciprocally, the knowing force can impress a new figure in it.

The external senses, "insofar as they are parts of the body, although we apply them to objects through action, viz., local motion, nevertheless properly sense through passion only, in the same way in which wax receives an impression from a seal" (AT X 412); that is, they are purely passive or receptive in sensation proper. He emphasizes that the comparison to an impression in wax is no mere figure of speech (per analogiarn ): we must think of the "external figure of the sentient body as being really changed by the object, just as that which is in the surface of the wax is changed by the seal" (AT X 412). This holds not just for touch but also for the eye ("the first opaque membrane that is in the eye receives the figure impressed by an illumination arrayed with various colors") and all the other senses (the first membrane impervious to the object "borrows a new figure from the sound, the odor, and the flavor"). Descartes notes further that we can conceive this more clearly if we make the supposition that the variety of colors, sounds, odors, and flavors corresponds to the great variety of possible two-dimensional figures. Next, just as the motion of one end of a pen gets passed on rigidly and instantaneously to the rest of the instrument as one writes, so does the stimulus of the sense organ get passed on "to a certain other part of the body, which is called common sense," and this common sense "functions like a seal for forming in phantasia or imagination, as if

[28] The individual rules consist of a rubric or heading and an exposition or commentary, with the exception of Rules 19 through 21, which have only headings. From Descartes's remarks at the end of Rule 12 and the beginning of Rule 13 it is evident that he intended to present thirty-six in all, divided into three groups of twelve.

in wax, the same figures or ideas^[29] that come, pure and without body, from the external senses" (AT X 414). After briefly explaining how phantasia can cause motions in the nerves to bring about the locomotion of the body, he ascends to the ultimate power, the vis cognoscens, "that force through which we properly know things," which is purely spiritual. Indeed, it is the particular functioning of this knowing force that produces the differentiation of the other faculties.

In all these [faculties] this force sometimes suffers, sometimes acts, and imitates now the seal, now the wax; which nevertheless is to be taken here only through analogy, for in corporeal things nothing at ail similar to this is to be found. And one and the same is this force, which, if it applies itself along with imagination to the common sense, is said to see, touch, etc.; if to imagination alone when [imagination is] arrayed with diverse figures, it is said to remember [reminisci]; if to the same [=imagination] in order to fashion new ones, it is said to imagine or conceive; if finally it acts alone, it is said to understand: the way in which this last occurs I will expound at length in its place. And therefore the same [knowing force] according to these diverse functions is called either pure intellect, or imagination, or memory, or sense; it is properly called ingenium, however, when it at one moment forms new ideas in phantasia, at another applies itself [incumbat] to those already made. (AT X 415-416)

Several things are immediately striking about this passage. The first is how closely imagination is coordinated with a physiological theory. In one sense, the imagination is a physical organ in the brain, identified no more specifically than by the term 'phantasia'. In another, imagination is the result of the knowing force applying itself to (or, more literally, bearing down upon) this organ. A second striking note is how central a role imagination plays in the functioning human being. The knowing force can act on its own—in that case it is called pure intellect—but in all other respects it acts upon or through the organ phantasia.^[30] Sensation is the knowing force

[29] In the Regulae, and even in many occurrences in the Discourse on the Method, 'idea' is synonymous with 'corporeal image'.

[30] A recent translation of Rule 12 obscures the relationship of the knowing force and phantasia to the common sense. The Latin clause "vnicamque esse, quae vel accipit figuras à sensu communi simul cum phantasiâ" (AT X 415 U. 16-18) is rendered as "it [the knowing force] is one single power, whether it receives figures from the 'common' sense at the same time as does the corporeal imagination"; see CSM, 1:42. This translation implies that the phantasia and the knowing force are simultaneously but separately applying themselves to the common sense. But this is to read the phrase "simul cum phantasiâ," a prepositional ablative, as though it introduced an elliptical subjunctive clause, with 'phantasia' in the nominative (compare the last line of p. 415, which has a parallel ablative expression in "vis, quae, si applicet se cum imaginatione ad sensum communem"). Moreover, 'simul' probably should not be taken in the strictly temporal sense but as joined with 'cum' to express a sharing of action (i.e., 'together with'); s.v. 'simul', Oxford Latin Dictionary, ed. P. G. W. Glare (Oxford: Oxford University Press, for the Clarendon Press, 1982) Haldane and Ross rendered this with the more defensible "it is a single agency, whether it receives impressions from the common sense simultaneously with the fancy," which at least leaves the construal open; see The Philosophital Works of Descartes, 2 vols., ed. and trans. Elizabeth S. Haldane and G. R. T. Ross, corrected ed. (Cambridge: Cambridge University Press, 1931), 1:38. Note also that just a few lines down from the clause in question, imagination is given a role in all acts of the knowing force, except when that force arts on its own (AT X 4151. 27-4161. 12). My preferred reading is "one and the same is this force, which, if it applies itself along with imagination to the common sense. . . ."

applying itself in diverse ways to the common sense "along with imagination"; reminiscence is this force applying itself to imagination alone insofar as there are figures already impressed there; imagining (or conceiving, a not unimportant alternative that we shall explore presently) is the knowing force applying itself in order to produce new figures. Even the motion of the body depends on imagination: "It is to be conceived that the motive force, or the nerves themselves, takes its origin from the brain, in which there is the phantasia, from which these [nerves] are moved in various ways, just as the common sense [is moved] by external sense, or just as the whole pen [is moved] by its lower part" (AT X 414-415). This conception can even be used, Descartes says, to account for "all movements of other animals, although in these absolutely no cognition of things be admitted, but only purely corporeal phantasia; likewise as well in the way all those operations happen in ourselves that we accomplish without any assistance from reason" (AT X 415). Thus imaginatio-phantasia—the former term implying chiefly the activity of making images, the latter the organ where the images are formed—is at work in virtually all activities of the human being, with the apparent exception of pure intellection.^[31]

What should we make of this passage? It is tempting to interpret it simply as an early version of the theory of the conarion or pineal gland, which is in fact located in the ventricles of the brain.^[32] In the early 1630s,

[31] In the Regulae, 'imaginafio' sometimes refers to the organ, but more often it refers to the power of imagining; 'phantasia', by contrast, refers almost exlusively to the organ and activities of imagination insofar as they are understood as the act of an organ. The degree to which pure intellect constitutes an exception from imaginative involvement will be discussed later.

[32] The pineal body or gland is an outgrowth of the roof of the diencephalon, one of the three parts of the forebrain. It is on the uppermost part of the brain stem, which is tucked away into the concave bases of the brain hemispheres (known as the ventricles); the pineal gland is, specifically, in the third ventricle. It is one of the few brain parts that do not develop bilateral structures, and it is near the thalamus, where all the nerves from the senses (except for smell) come together. Descartes says that he chose the pineal gland as the central organ of the sensory system because he thought it was the only place for the two channels of information from the right and left side sense organs (e.g., the right and left eye) to be unified into a single impression (see L'Homme, AT XI 174-177; Dioptrics, AT VI 128-130; and Passions, AT XI 352-353).

Descartes expressly identified this gland as the focal point of bodily activity: external impressions are conveyed to it from the sense organs by means of motions transmitted along the nerves, and, in turn, it is the source of flows of the so-called animal spirits that produce the animal's body motions. The mind, which is a radically different kind of substance from body, somehow takes note of what is happening to the pineal gland and is able to produce motions of that gland. Precisely how such things happen between radically distinct substances, the main problem of mind-body dualism, has exercised generations of Cartesians and critics, of course. At any rate, Descartes conceived thinking and body to be intimately although mysteriously joined in human beings. Most people are unable to conceive them as distinct because of this intimate joining, a fact that sets the main problem for Descartes's principal works, in particular the Meditations, which appears to teach that we can come to a pure experience of ourselves by turning away from reliance on the senses and imagination.^[33]

Interpreting phantasia merely as the protopineal gland seems quite natural. Nevertheless, a closer look can help clarify small but significant differences between the phantasia of the Regulae and the pineal gland of Descartes's later work. The pineal gland is the "command center" of the autonomous mechanical system that is the body. 'Autonomous mechanical system' means that the body's functioning is explained by the mechanical laws of the material universe. Within this system the pineal gland is affected by motions of nerves and flows or currents of the animal spirits, and it uses these motions and flows to direct new flows that produce body motions and other physiological responses. This system, which is at work in both animals and the human being, requires no consciousness to function accurately and effectively. A lamb flees from a wolf because the nerve motions and spirit flows elicit this as a mechanical reaction; likewise a human being withdraws a hand from the searing heat of a flame, or might flee at the sight of a wolf, because of such mechanical operations. But in the case of a human being facing a wolf, "might flee" is the exactly appropriate locution, because there are the additional factors of mind and will. The presence of the wolf can trigger an automatic response, but it might also set the mind to work on the question of what to do. If a solution to the situation appears, the mind, through its intimate fusion with the pineal gland, can induce gland motions that trigger the appropriate bodily mechanisms implementing what the mind has decided. This mind-body interaction is what is conventionally understood as a key element of Cartesianism.

[33] Later, in chapter 6, I shall suggest that although the Meditations does teach us how to turn away from the corporeal powers, it does not teach that the essence of human being is mind apart from body.

In Rule 12, however, Descartes uses a vocabulary more psychological than mechanical to describe what happens on the way from sense organ to phantasia. Sensus communis, imaginatio, phantasia, and memoria are of course the inward or internal senses that played an important role in Scholastic and Renaissance psychology, in particular in accounts of the progress of a sensibie species from sense organs to the higher sensitive faculties. The Regulae describes a transmission of impressions, but this way of conceiving things is not necessarily a modern trait: Aristotle himself used the image of the signet ring impressing its shape into wax to illustrate the process of sensation. The impression that Descartes describes is not in the first instance an impression of a mechanical motion or force but rather the impression of an image.

If we attend carefully to Descartes's explanation in Rule 12, we see that it is not intrinsically mechanistic at all. There are no atoms, no collisions, no transmission of motion and nothing but motion. Of course, Descartes describes a motion that takes place instantaneously, like the simultaneous motion of all the parts of a pen, but its purpose is not to reduce sensation to motion but to illustrate how an impression or figure made on a sense organ can be transmitted without lapse of time. Moreover, the transmission of the impression sketched in the Regulae takes place as a whole, that is, as the transmission of an integral image, whereas in Descartes's later physiological accounts the impression is broken up into many discrete motions because of the multiplicity of individual nerve fibers that are involved in the transmission of sensation.^[34] Nor is it clear from the Regulae passage what the medium of transmission is. It is not clearly the nerves, since they are discussed only as the medium for producing the locomotion of the body (like raising one's arm or walking), and there is no mention of the involvement of animal spirits. Unlike the case of the purely mechanical pineal system, the emphasis in Rule 12 is on the internal senses and their relations to one another, that is, on traditional topics of medieval and Renaissance psychology with their organic correlates.

A perhaps more pregnant difference between phantasia and the pineal gland is suggested by a simple synonymy noted in the passage. When the knowing force applies itself to the imagination in order to form new figures, it "is said to imagine or conceive." The conjunction of imaginari and concipere suggests that imagination is being taken, not in the restricted sense of a power that merely forms images, but in a more expansive one that regards it as a truly cognitive power.^[35] The importance of this synonymy is

[34] See Dioptrics, AT VI 146.

[35] The Meditations, of course, uses 'imaginari' in a more restricted sense. The synonymy between the two Latin terms is to be found also in a very early work from late 1618, the Compendiurn musicae ; see chap. 2, Sec. A.

reinforced when one considers that the formal definition in Rule 3 of intuitus, which is the fundamental way of knowing taught in the Regulae , calls it a concept (conceptum ) of mind (mens ). Conceptum is, of course, the past participle of concipere. Is it possible that Descartes had in mind something like the medieval notion of an imaginatio that is not just an internal sense but also an intellectual power capable of exercising the simplest and most basic act of mind, the act of intuiting a concept?

Another question is intimated by Descartes's remark that the knowing force not only notices images present in phantasia but also applies itself to the common sense with imagination (cum imaginatione ) in the process of seeing, touching, smelling, and so on. That is, not only is there an extra organ involved in sensation, the sensus communis, but the mind itself, under the name vis cognoscens, acts on it and seems in this sense to be more deeply involved in the human body than is the intellect that acts on the pineal system. In the pineal system the gland is the unique location for direct body-mind interaction; the mind can act directly there but nowhere else. If Descartes had already worked out his two-substance metaphysics and the corresponding theory of the human being when he composed Rule 12, we would have to conclude that this formulation is at best slovenly. But it is not at all clear that he had worked it out. Indeed, it is likely that he did not work out the foundations of his mature metaphysics until after he had given up the Regulae.^[36]

These few "facts" about differences between the early and the later Descartes are insufficient in themselves to bear the weight of the thesis that the Regulae presents a conception of imagination, human cognition, and the relation between body and mind that is radically different from the one we ordinarily attribute to Descartes. Yet they are clues leading us deeper into the problem of understanding Descartes's thoughts before 1630 and thus also into the questions of where, why, and how he may have changed his mind about things. Moreover, the psychophysiological hypothesis of Rule 12 doubtless reveals something important about the intentions of the project of the Regulae , for at least three reasons. First, at the outset of Rule 12 we are told that the "rule concludes everything that has been

[36] Another important difference is that in the pineal system one really should not say that the mind produces images in the pineal gland, or even that images are formed on its surface. This claim may seem eccentric, given later texts that describe an image being formed on the gland's surface (e.g., AT XI 176 and 355-356). As shall gradually become clear, however, Descartes's later, purely mechanical conception of the processes involved in the motions and effects of nerve and animal spirit motions undermines the legitimacy of reference to images in any literal sense, and therefore such references might be interpreted as a throwback to the prepineal accounts. See chap. 7. An account of the accepted understanding of Descartes's physiological psychology can be found in Gary Hatfield, "Descartes' Physiology and Its Relation to His Psychology," in The Cambridge Companion to Descartes, ed. John Cottingham, 335-370 (Cambridge: Cambridge University Press, 1992).

said above [in the previous rules], and it teaches in general what will be^[37] explicated in particular" (AT X 410-411); thus it seems to serve as a linchpin to the argument of the Regulae , both as a summing up of the first part and an introduction to what follows. Second, although Descartes introduces the psychophysiological hypothesis as suppositions that will help the reader to conceive what he does not have space to expound at length (implying that he could do so), he says that they "diminish nothing of the truth of things but only render everything clearer by far" (AT X 412). Descartes must believe that this imaginative hypothesis is really true or at least gets at a basic truth. Third, we should remind ourselves that the passage discussing the names corresponding to the various activities of the knowing force concludes with the definition of a faculty that was not among the standard Scholastic faculties but that nonetheless is crucial to the Regulae, ingenium. The importance of this definition should be obvious, since after all it was for the purpose of the direction of the ingenium that the Regulae was composed.^[38] Yet hardly anyone has taken notice of the significance of this term. As we shall see in the course of our discussions, understanding precisely what ingenium is, is of capital importance for understanding what Descartes's early philosophy is about.

We are not yet in a position to tackle the nature of ingenium, however. We shall discover eventually that the cultivation and direction of ingenium was Descartes's response to a problem that he had been thinking about for years, the role of the internal senses, specifically of imagination, in knowing. We must therefore first look into the problematics of imagination and the internal senses in the earliest writings and documentation available. We shall begin by turning back to 1618, a year that marked a decisive turn—probably the decisive turn—in Descartes's life.

[37] AT has the past tense; A, H, and N, the future.

[38] The title as Descartes intended it is somewhat conjectural, since no original manuscript is extant. In particular, the traditional Regulae ad directionem ingenii probably should be amplified by something like "de inquirenda veritate"; see Marion's discussion in Règles utiles et claires pour la direction de l'esprit en la recherche de la vérité: Traduction selon le lexique cartésien et annotation conceptuelle, trans. Jean-Luc Marion, with mathematical notes by Pierre Costabel, Archives Internationales d'Histoire des Idles, no. 88 (The Hague: Martinus Nijhoff, 1977), 85-87. From the frequency of the occurrences of 'ingenium' and 'ingenia' in the rule headings and commentaries, there can be little doubt of the term's central thematic importance: it appears in five of the first twelve rule headings, and among nouns ingenium is tied for total number of occurrences with figura (60 each), trailing only cognitio (62), ratio (64), regula (69), and the generic res (157).