SOURCE: "Albert on the Psychology of Sense Perception," in Albertus Magnus and the Sciences: Commemorative Essays 1980, edited by James A. Weisheipl, Pontifical Institute of Mediaeval Studies, 1980, pp. 263-90.

[In the following essay, Steneck explores Albert's theory of sense perception, arguing that it typifies the general level of scientific understanding in the field at the time.]

By the mid-fourteenth century, when the anonymous Tractatus ad libros Aristotelis … was copied, most Latin writers in the scholastic tradition held in common a conceptualization of sense perception that served well the needs of natural philosophers, theologians, and physicians alike. While there was debate about the fine details of this conceptualization, its basic outline was clearly understood by all involved. Two centuries earlier, when Adelard of Bath wrote his well-known Quaestiones naturales, the situation was quite the reverse. Numerous ancient teachings on sense perception were known in part, but no single theory was available to tie these teachings together and provide a common ground upon which further debate could take place. In the events that transpired between these two stages in the history of psychology one figure that stands out above all others as playing a major role is undoubtedly Albert the Great.

The development of the psychology of sense perception between the twelfth and fourteenth centuries is evident in a comparison of the writings of Adelard with the assumptions that are implicit…in the Tractatus ad libros Aristotelis. Adelard clearly was working within the general framework of the ancient tradition of sense perception when he wrote:

whatever operation of this sort the mind performs in the body, it performs with a certain amount of assistance from the body and this is done one way in the brain in another in the heart and in yet another in the other members [i.e., in the senses].

But Adelard was not aware of most of the details of the ancient theories that lay behind this framework. The highly organized, almost mechanistic view of the body that was so familiar to the author of the Tractatus, the view that tied the five external senses to the brain by connecting nerves and then localized a number of internal senses (usually four or five) in the cells of the brain, had yet to find its way into the Latin West through the writings of Aristotle and his commentators. Since Albert played an important role in bringing these works to the attention of his contemporaries, it should come as no surprise that by virtue of this role he became an important figure in the history of the psychology of sense perception.

That Albert did play an important role in the development of the scholastic theory of sense perception was widely recognized by fourteenth-century contemporaries of the anonymous author of the Tractatus. In their discussions of the actions and localization of the senses, Albert's name is the only contemporary one (post 1200) mentioned with any frequency and with an authority equal to that of the ancients. Even though he may not have been the first writer to sort through the newly translated works of Aristotle, Avicenna, Averroes, and others with an eye toward elucidating and systematizing their thoughts, he was clearly the author quoted (and presumably read) when a weighty opinion was needed to settle a dispute among these authorities. The reason for this is not difficult to understand. The comprehensiveness of Albert's discussion of sense perception in the Summa de creaturis and later works far exceeded that of other thirteenth-century writers and made them an ideal introduction to the topic at hand. For our purposes they provide as well an entry into the scientific thought of this important scholastic.

The hundreds of folios that Albert devoted to the problem of sense perception make the task of summarizing his thoughts on this subject a difficult one. However, over the course of his lifetime his psychology of sense perception seems to have changed very little; the basic description set out early in his career in the Summa de creaturis is followed fairly closely in his commentary on De anima and the Parva naturalia and is implicit in De animalibus and miscellaneous references to the senses in works not devoted strictly to science. As a result, his earliest major treatment of sense perception in the Summa is in general a good guide to this aspect of his thought, and it will be focused upon first. Thereafter, the later works will be drawn upon to help round out Albert's views on sense perception and place them very briefly into an overall epistemological and methodological framework. This latter discussion is designed to explain in part how Albert, and other scholastics, could spend so much time discussing how the senses functioned while still falling far short of developing a rigorous psychology of sense perception.

A. SUMMA DE CREATURIS

For Albert, as indeed for most scholastics, the topic of sense perception was most commonly broached within discussions of the soul and its powers. The soul, which is one in substance and the active form of the body, moves the body in many ways. It does so not because it consists of several individual souls or a number of substances—one soul is not responsible for sense perception and another for reason—but because the one soul of the body exerts its actions in different ways (called powers of the soul) in the many parts of the body. Or conversely, the parts of the body can be said to pervert or corrupt the activities of the soul in different ways, thereby accounting for its many powers. Just as an old man who receives (accipiat) the eye of a young man will see like a young man (sicut juvenis), so too the remaining senses and even the rational soul will act differently depending on the organs of their activity.

Given this general definition of the soul and its powers, the investigation of sense perception very rapidly came to focus on four basic issues: the precise definition of the sense (power of the soul) under consideration, its organ, its mode of action, and the medium or media that are responsible for initiating its activity. Definition clearly established which of the powers of the soul was being discussed; the question of organ established a proper part of the body for each power to act through; the discussion of actions explained how each power actually acts through its organ; and the discussion of medium tied the actions of the senses to external stimuli. Except for a few general questions, Albert's discussion of these issues, which proceeds sense by sense, comprises the psychological portions of the Summa.

i. The Definitions of the Senses

Albert's classification of the senses has led to a great deal of controversy among modern scholars regarding his consistency.I have dealt with this issue elsewhere and endeavored to show that the apparent inconsistencies that previous scholars have pointed to in his works involve differences in his use of terms and not in his overall conceptualization of sense perception. Throughout his writings Albert remains faithful to his particular understanding of the Greco-Islamic tradition he received, as described initially in the Summa. According to this tradition the actions or powers of the sensitive soul can be divided into two major subgroupings, the external and the internal senses, with the former including the five proper senses—vision, hearing, smell, taste, and touch—and the latter three, four, or five internal powers, depending on the authority followed. (Albert discusses five such powers in the Summa; common sense, imagination, phantasy, estimation, and memory.) The distinction being pointed to here is the distinction between those senses (the external senses) that have the capacity to sense only that which is proper to them alone (their proper sensibles) and those (the internal senses) that respond in one way or another to information received from many senses.

The fact that each of the five external senses was assumed to have a proper object or objects that it alone can perceive and that each was assumed to reside in a proper organ provided sufficient information to establish suitable definitions for them. Thus Albert at one point defines vision as the power that has its seat of activity in the eye (visus sit vis ordinata in oculo), taste the power that is limited to the nerve that covers the surface of the tongue (diffinitus a nervo expanso in superficie linguae), and so on for the other senses. Similarly, vision can be defined as the sense that perceives color, hearing the sense that perceives sound, smell the sense that perceives odor, and so on for taste and touch. This much was fairly evident. Few commentators who dealt with the external senses had trouble defining each of the five commonly assumed ones.

However, the fact that suitable definitions could be established for five of the external senses did not end the problem of definition. If other organs or sensibles exist, beyond those associated with vision, hearing, smell, taste, and touch, then it might be possible to argue that there are other senses that need to be defined. Albert resolves this issue by demonstrating that animals need only five external senses and therefore there are no additional ones. The senses serve two functions: they preserve the being of the living creature (ad esse), and they allow it to survive in some semblance of comfort (ad bene esse.) For preserving the being alone the living creature needs to grow (ad esse constituendo), which requires touch, or simply to survive (ad esse conservando), which requires taste. To preserve well-being, sense is needed either to regulate eating (secundum regimen in cibo), which requires smell, or to pursue progressive motion (secundum regimen in motu processivo.) The latter encompasses both direct and circular motion, which require vision and hearing respectively. Since these are the only senses that are necessary and since nature provides only that which is necessary, it can safely be argued (posset probare) that there are only five external senses.

Having established that there are five and only five external senses Albert turned next to a related problem, their order. When faced with several entities in a single larger grouping, the scholastic mind frequently attempted to arrange these entities in a hierarchy, to establish a first sense and a last sense among the external senses. Since, according to Albert, this order can be established in at least two ways, the first and last among the senses differs. If the senses are judged on the basis of their capacity to contribute to one of the most fundamental properties of an animal, its power to sense, then touch is of primary importance. Touch is the only sense that animals cannot live without. Since "in the destruction of touch the animal is destroyed and this is not so for the other senses, namely for hearing, vision, smell, and taste," touch constitutes the foundation (fundamentum) of the other senses. If, however, the senses are ordered not in terms of what actually makes an animal an animal (in constituendo animal) but in terms of the primary function of the sensitive soul, cognition (secundum … rationem cognitionis), then vision is first and touch last. We receive more information through vision than the other senses, followed by hearing, smell, taste, and touch. How the senses are ordered depends, therefore, on the criteria that are used for ordering.

The internal senses, like the external senses, were sometimes defined by reference to either the object or organ of their activity. However, since the internal senses all reside in one organ, the brain, and seem not to receive distinct stimuli, definition via object and organ did not produce a very precise understanding of their division.

For example, on the basis of the object of perception Albert notes that one internal sense (internal by virtue of the fact that it resides within the brain), the common sense, apprehends through things that are external to the brain (apprehensiva deforis), while the remaining four senses (imagination, estimation, phantasy, and memory) apprehend through things that are within the brain (apprehensiva deintus.) But this distinction does not do justice to the many senses that reside within the brain. As a consequence, Albert tends initially to accept the fivefold classification of Avicenna (common sense, imagination, phantasy, estimation, and memory) and waits to distinguish them more precisely from one another on the basis of their actions, as will be discussed in the next section.

ii. The Acts of the Senses

Since sense perception, within the framework of an Aristotelian epistemology, must of necessity be initiated by the actions of external objects, the senses, as recipients of these actions, were commonly understood to be passive powers. "It must be said, in accordance with the pronouncements of all the philosophers, that 'sense' is a passive power and that it is said to be acted upon." However, as passive powers the senses do not undergo physical, form-matter transformations. If they did, the action of the form of light on the eye would change it to light, which clearly does not happen. In sense perception, "there is no physical alteration in the soul" (in anima nulla est alteratio physica). Therefore, the act of sensing can be described as the senses being acted upon but not being acted upon by the forms of objects per se. Instead, the senses are acted upon by the repreresentatives of the objects, called sensible species, which convey the active intention of the object and not the form of the object itself to the senses. When this happens the senses, as passive powers, receive (accipit) these intentions and perception takes place.

Although there is no physical alternation of the senses during perception, sense perception is a physical process. Moreover, it is only when the soul and body are in proper harmony with their sensible species that sense perception takes place. Such harmony is established through three successive activities: first, the power of the soul is joined with its organ; thereafter, its disposition is established through the activity of the animal spirit and the natural heat and harmony of the organ (dispositio fit per spiritum animalem et calorem naturalem et harmoniam organi); and finally, the sensible species are received (quando vero habet speciem sensi-bilem). At this last stage, the passive power of the soul apprehends its proper object and the act of perception is completed (tunc est potentia completa per actum).

The grounding of the passive action of each of the senses in one organ not only establishes the mechanism through which sense perception takes place but also the object that each of the senses is able to perceive. Unlike the intellect, which is able to receive all intelligibles (potest recipere omnia intelligibilia) because it does not operate through an organ, the senses, whose organs are not made to receive all sensibles (organum suum non est fabricatum ad naturam omnium sensibilium), receive only those sensibles that are proper to them, their proper sensibles. This is why the eye receives only color and not sound or smell or some other sensible, and so on for the other senses. In sum, it is the nature of a sense, as determined by the soul acting through and being influenced by the potency of its organs, that determines its actions. The nature of the eye is to perceive color, and vision, which is the proper action that the sensitive soul exerts through the eye, is the action of the eye.

The coincidence of sense and proper sensible serves one additional function besides confining particular pieces of information to particular senses. The coincidence of sense and proper sensible provides the assurance in the chain of cognition from object to intellect that the information that is perceived by the senses is correct. A sense acting in accordance with its proper sensible does not err (non contingit errare). It may err with regard to information that is not within the bounds of its proper sensible, such as when the sense of vision attempts to determine the composition of a particular color (circa compositionem colorum), but it does not err when it perceives the information that pertains strictly to its proper sensible—that the colored body is red or green and so on. To this extent, sense cognition can be said to be true and accurate.

Having set out this general framework for understanding the acts of the senses, the specific details that Albert relates for each one, particularly for the external senses, are fairly straightforward. The act of vision is to receive the sensible species of color, the act of hearing to receive the sensible species of sound, and so on for taste, smell, and touch. Nonetheless, there is always room for subsequent debate and questioning.

In his discussion of vision Albert launches into a lengthy recapitulation of past opinions, particularly those of al-Farābi (Averroës) in De sensu et sensato and Avicenna in De anima, which discussion prompts him to append a detailed analysis of a problem that had long currency in discussions of vision, the problem of extra-versus intromission theories of vision.

A full assessment of the act of hearing rests on an understanding of the exact location of its organ, as will be discussed in the next section. As to the object of hearing, sound, Albert queries whether or not it comes to the ear very rapidly (subito), as does light. He concludes that it does only if that which produces the sound is very close, thus making the time of transmission imperceptibly small. Otherwise, hearing requires time (percipitur tempore).

Clarifying the act of smell leads Albert to question whether or not different animals can smell the same odor differently. Since odors initiate the act of smell, it would seem that the same odor would produce the same act in all animals. This obvious inconsistency— some animals can smell better than others—is resolved by pointing out that since the organ of smell is closely associated with the brain and since the brains of animals differ in their dispositions, animals smell differently. The sensible species of smell are able to act upon the dry brain of some animals much more easily than the wet, cold brain of humans, and consequently these animals have better senses of smell.

Finally, the definition of the acts of taste and touch depends upon resolution of the problem of whether they comprise one sense or two. It was sometimes suggested that they do not comprise two separate senses since they seem to have the same objects (hot, cold, wet, and dry) and are at times in the same organ—we both feel and taste with our tongue. However, since the act of taste is to judge flavors (judicium saporum) and the act of touch to judge that which can be felt (tangibilium judicium), they are, Albert concludes, two separate senses.

The simple data received directly from proper sensibles accounts for only a small portion of the information that is eventually known about an object. Moreover, since each of the senses apprehends only its own proper sensible, none is able to compound this information with information received in other senses and form a composite image of an object: that a particular tree is green, has the smell of pine, and so on. Consequently, Aristotle and most of his commentators argued in favor of the existence of a common sense to receive species from the external senses and form them into a composite image of the object. Having formed this composite image, common sense then has the capacity to compare the composite image of one object with that of another and reach comparative judgments about two objects: that one object is sweeter or whiter than another object. Thereafter the sensibles species received from the five external senses are passed from the common sense to the imagination, the second internal sense, where they are stored for future reference or further transmitted to phantasy, estimation, and memory, the three remaining internal senses.

The fact that imagination stores the images of things in their absence means that an entirely new type of sensitive action begins, the internally apprehensive action. From this point on in the cognitive process, additional sense data can be derived even in the absence of any material object simply by reflecting upon (imagining) the images that are stored in the imagination or the memory. But imagination does more than store images. It also prepares them (praeparat imaginationes quadrupliciter aliis virtutibus operantibus in ipsa) for the future actions that will follow (1) in phantasy and estimation, (2) in memory, (3) in the intellect, or (4),by a reflowing action, in common sense. In this way, Albert is able to incorporate into this power the comprehensive actions assigned to imagination by John Damascene, Gregory of Nyssa, and Augustine.

The need for additional internal powers, besides common sense and imagination, stems from the fact that animals and humans apprehend certain things that are not sensed by the external senses. The most common example given in support of the contention was a sheep apprehending the hostility of a wolf and fleeing even though it has never seen a wolf before. Obviously some internal power, in this case "estimation," is called for to evaluate the suitableness or unsuitableness of the intent (intentio) of an object by a special apprehension and thereupon motivate the apprehending creature to approach or flee from the object (sit determinare de fugiendo et imitando per apprehensionem convenientis et inconvenientis). Since this additional information is of great importance in directing the actions of animals, a fourth internal power, phantasy, was added, which has the capacity to compose and divide intentions with the less complex information that is received in the common sense and stored in the imagination. Phantasy also has the power in humans to act under the influence of the intellect, thereby making it in some ways a cogitative power (vis cogitativa). And then ultimately all of this information is stored in the memory where it can be recalled by the simple action of the senses (true memory) or by the intervention of reason (reminiscence), thereby completing the acts of the internal senses.

iii. The Organs of the Senses

Interest in the organs of the senses arose to large extent after the time of Aristotle. To be sure, there were numerous references to sense organs scattered through his writings, but the systematic localization of the senses, particularly the internal organs, in specific parts of the body had to wait for the anatomical writings of Galen to be fused with the Aristotelian corpus by later commentators. Few Latin writers in the thirteenth and fourteenth centuries paid more than routine attention to this aspect of sense perception. Writers such as Thomas Aquinas mention the organs of the senses, but seldom in any detail or with an eye toward actual organic placement. Albert does not share this common disinterest. Throughout his writings it is clear that he is localizing the senses in an anatomically real body and not simply repeating descriptions handed down from an earlier tradition. This is especially true of the discussion of the senses in De animalibus (as noted below), but also to a lesser degree is the conclusion reached from a careful reading of the Summa de creaturis.

Of all the sense organs, Albert pays the most attention by far to the organ of vision. Here he is following a long tradition that extended from the writings of Aristotle through those of Avicenna and Averroes (his principal sources) to the works of his own contemporaries. In reviewing this tradition, Albert attempts to steer a middle course between Gregory of Nyssa, who held that vision resides in the forepart of the brain, and Avicenna, who assigned vision to the optic nerve and crystalline humor, by outlining three stages through which the act of vision proceeds. Vision begins in the sensitive portion of the eye (the crystalline humor), where the sensible species of color is received, is advanced toward greater perfection in the optic nerve, where it is mixed with the sensitive spirit, and is perfected (finally and completely perceived) in the anterior part of the brain. Thus to a certain extent the eye, the optic nerve, and the brain can each be considered to be the origin of vision, depending on the definition of the act of perception being considered.

The appearance of the auditory nerve, as described by Aristotle and his followers, led to some confusion regarding the act of hearing. According to this description the auditory nerve is hollow and contains within it, as it extends from the brain to the tympanum of the ear (apparet versus tympanum auris), air that is similar to the air outside the ear (claudat in se partem connaturalem aeris). It would seem, accordingly, that the ear and its nerve are capable of receiving sound as it exists materially in the air (esse soni secundum materiam), thereby obviating the need for sensible species. However, since apprehensive powers can only perceive immaterial species (speciem sine materia ejus), clearly this is not how hearing takes place. Albert concludes, therefore, that air is in contact with the auditory nerve only at its beginning (aer tangit nervum in principio sui). Beyond this point, in the spirit that flows outward from the brain to the tympanum, only sensible species are impressed (non imprimitur nisi species soni). Thereafter, if hearing follows the same path as vision, these species would be carried to the brain where the act of hearing would be completed.

After passing briefly over the organs of smell and taste, which one assumes begin in the nose and tongue respectively, are perfected in the connecting nerves, and completed in the brain, Albert turns to the difficult problem of touch. At first glance touch appears not to have a single organ but to be diffused throughout the body and to perceive objects in and of themselves without the intervention of an external medium. Albert agrees that in one way this is true. As the first of the senses, touch is the form and perfection of the animate body (est forma et perfectio animati corporis) and therefore has the entire body as its organ (pro organo) and senses without a medium. Its capacity to sense in this instance depends on the degree to which a particular part of the body is influenced by the sensible spirit (participant spiritum sensibilem). Those parts that are influenced the most, such as nerves, flesh, and skin, sense better than those that are influenced the least, such as bones, brain, and hair. The latter, Albert suggests, sense

insofar as they are surrounded by membranous nerves, in the breakdown of which, such as around the brain and around the bones, pain is sensed.

As the last of the senses, touch is simply the sense that receives tangibles, and in this case it acts like the other senses; it is completed in the brain, perfected in the sensible spirits that flow out from the brain through the nerves of the body, and begun in the flesh. In this latter way touch senses those qualities that have opposites and are active toward touch (prout habent contrarietatem et motum ad ipsum), such as hot, cold, wet, and dry. In the first way, touch senses those things that are harmful and beneficial to life (quod est dissolvens continuationem talis corporis, et. … conservans), such as the pain of a flogging or the pleasure of intercourse.

Since Albert most commonly holds to a fivefold classification of the internal senses, his need with regard to their localization is to find five loci for them within the three Galenic cells of the brain. Avicenna, Albert's primary source for localization, had accomplished this by assigning two powers to the anterior cell (common sense and imagination), two to the middle cell (phantasy and estimation), and memory to the posterior cell. Albert agrees with this description, but adds one qualification. The two-two-one arrangement, Albert argues, applies to the senses of animals. The internal senses of animals are not, however, entirely analogous to those of humans. In humans the internal senses are in one crucial way decidedly different, and that is insofar as they act as a cogitative power that is influenced by the intellect. Albert assigns this cogitative activity to the middle portion of the brain and to accommodate it moves phantasy and estimation in humans toward the anterior cell. This displacement prompts him to present the unconventional conclusion that in humans the anterior cell of the brain has four powers: common sense, imagination, phantasy, and estimation.

B. LATER WORKS

i. De anima

The years that passed between the writing of the Summa de creaturis and the commentary on De anima undoubtedly afforded Albert the opportunity to read more widely and reflect more deeply on, among other issues, the problem of sense perception. Certainly this is the impression that is received on turning to the commentary on that portion of De anima that begins the treatment of the senses (II, tr.3). The clear delineation of problems and the structured presentation of the opinions of previous authorities give every indication that Albert's thoughts on this subject are now firmly established and that he is himself fully in control of the material being presented. Although his basic psychology of sense perception seems to have changed very little in the dozen or so years that separate the two works, his confidence in and mastery of this psychology seems to have grown and matured greatly.

Albert's increased mastery of the problem of sense perception is evident in more than his style of presentation. By the time he commented on De anima he had clearly thought through and was prepared to make explicit a suggested metaphysical unity to sense perception that is implicit but never clearly articulated in the Summa. His thoughts on this subject are presented early in the sections on the senses as "a digression explaining the degrees and manner of abstraction" (digressio declarans gradus abstractions et modum). In this digression Albert looks beyond the common element that had informed his discussion in the Summa, the common element of the senses as powers of the sensitive soul, and seeks to uncover the unity of the metaphysical process that underlies all perception. He presents this unity in the form of an explanation of the way in which the senses can be arranged hierarchically through a consideration of their relationship to the objects of perception.

Building on the same basic definition of perception set out in the Summa, "to apprehend is to accept the form of that which is apprehended" (apprehendere est accipere formam apprehensi), Albert notes that that which is accepted, the representative of the object (intentio ipsius et species), is received in four distinct ways.

The first and least abstract way is when the representative of the object is accepted in abstraction "from its matter but not from its presence or its appendices" (a materia, sed non ah eius praesentia nec ab eius appendiciis). This is the abstractive level of the externally apprehensive power (vis apprehensiva deforis), which, Albert notes, is sense (quae est sensus). By sense there can be little doubt that he is including, as he had in the Summa, the five external senses and the common sense.

The second level of abstraction contains imagination, which apprehends the form of the object apart from both its presence and matter but not in abstraction from the conditions or appendices of matter (sed non ab appendiciis materiae sive condicionibus). By "conditions" Albert is referring to the attributes of the form as it exists or existed in a particular subject.

At the third level of abstraction the intentions (intentiones) of the form are known by estimation and the compounding action of, one assumes, phantasy and estimation (et numquam est sine aestimatione et collatione).

And lastly, the form is known simply and separated from all the prior conditions. This is the cognition that is achieved solely in the intellect.

Translating this description into more concrete terms and adding to it the initial advances toward the complete perception of proper sensibles that take place between the senses and the brain, Albert would describe the process of apprehending an object, such as a particular person, as follows. When that person is present before us, its species, or representative is accepted by the organs of the external senses, where perception begins. The species received in the external senses are then transmitted by the sensitive spirits that flow in the connecting nerves to the brain, where a composite image of the object is formed. These steps take place only in the presence of the object. Thereafter, the form of the object is transmitted to the imagination and at the same time abstracted from the presence of the matter. We now know the form of the person even if that person should leave, but we know this form only as it existed in that person and not as it could have existed in another person (in uno individuo unius speciei, quod non sunt in alio). That is to say, we as yet do not apprehend the form of "homo" apart from a specific set of attributes—a particular placement of limbs, facial color, age, and so on—belonging to the person originally perceived. At the third level of abstraction, certain tangential information, called "intentions" (intentiones), is apprehended by phantasy and estimation, such as the potential friendly or unfriendly nature of the person in question. This is information that is received along with the sensible species but not impressed in the senses (cum sensibilibus accipimus, et tamen eorum nullum sensibus imprimitur). Finally, at the level of the intellect the form "homo " is known as a universal concept, now in abstraction from all specific limiting features associated with the existence of that form in a particular subject.

Having established the physiological background for dealing with sense perception, Albert then continues his discussion of the external senses along the same general lines followed in the Summa. Under sight he once again focuses on the proper sensible of vision and the manner in which it is transmitted to the eye. His discussions of hearing, smell, and taste entail detailed considerations of the nature of sounds, odors, and flavors and the manner in which they are transmitted from object to sense organ. In fact, the only major difference between these two works, from the point of view of this study, is their corresponding treatments of the organs of perception. In line with Aristotle's own discussion of the senses De anima> and unlike his earlier interests expressed in the Summa, Albert for the most part ignores the problem of localization in De anima. The only exception to this generalization is found in his discussion of touch. The lack of any obvious sense organ for touch had prompted Aristotle to discuss its localization in some detail, thus providing Albert with an opportunity to consider at least this one organ in De anima.

The reason given for a detailed consideration of the organ of touch is the apparent disagreement between Alexander of Aphrodisias, Themistius, and Avicenna on the one hand and Aristotle on the other over the role of flesh in touch. Aristotle clearly states that flesh is the medium and not the organ of touch, whereas the other three authorities argue that the flesh that is imbued with nerves (carnem nervosam) is the organ of touch. Albert's compromise, which is similar to one set out in the Summa but now discussed in more detail, rests on an understanding of the types of flesh that exist. True flesh (id quod vere caro est) seems to be what Aristotle has in mind by flesh and as such Albert does not object to calling it the medium of sense perception. However, flesh that has sensitive nerves mingled with it or that is situated in the vicinity of other senses does perceive what touches the body and as such can be considered the organ of touch. The manner in which flesh senses in the latter way is explained through mention of two apparent anomalies: flesh-like organs that do not sense and nonflesh-like organs that do sense.

It is clear, Albert argues, that the sensitive power of nerve-imbued flesh extends to parts of the body that are not flesh-like in appearance, such as teeth. Teeth obviously feel pain. The cause of this, Albert conjectures, is the vivifying influence of the surrounding flesh that is carried to the teeth along with the nutriments they receive. That teeth do receive nutriments from the surrounding flesh is evident from the fact that they sometimes regrow after being extracted (denies extractos recrescere) or that they increase in size when a facing tooth is removed (dentes superiores vel inferiores habet extractos … dentes illis oppositos super alios prolongari). This would only happen if the teeth were influenced by the nutriments of the body and explains how they can participate in sense perception. But not all nerve-imbued flesh senses, to turn to the second anomaly. The brain and liver, for example, were believed by Albert to have no sense capacity of their own. The reason for this is that the brain and liver are more influenced by their own qualities than by the surrounding flesh (quorum complexio ad medieiatem carnis non accedit) and hence do not sense. If we feel pain in these organs it is due to the nerves that surround them (hec est in panniculis, qui sunt circa substantias eorum) and not the organs themselves, as was noted above. The same would be true of the nerves of ligaments and sinews (funes sive ligamentum) that attach to bones and likewise do not sense. Ultimately, then, whether or not a particular part of the body can be said to be the medium or organ of touch depends on the vivifying and sensitive spirits that are active within it and the degree to which they are active.

Following his discussion of the external senses, Albert goes on to question whether or not they are five in number, as had Aristotle, and then orders the remainder of his discussion of sense perception with "a digression clarifying the five interior powers of the sensitive soul" (digressio declarans quinque vires animae sensibilis interiores). These powers are clearly delineated as common sense, imagination, phantasy, estimation, and memory, and localized within the three ventricles of the brain in accordance with the teachings of "the Peripatetics" (Peripatetici), in this case, Avicenna. Thereafter, the action of each is explained in turn and various problems discussed, such as an error of the ancients that maintained "that to know and to sense would be the same" (quod intelligere et sentire essent idem). A great deal of this material simply repeats the discussion of the senses in the Summa, although in De anima its organization is more straight-forward and easier to follow. Throughout, Albert's initial psychology of sense perception remains essentially that of the earlier work. If his views in De anima differ at all from those of the Summa it is in emphasis and not in content.

ii. Parva naturalia

The Parva naturalia turn from thinking about the soul in and of itself (secundum seipsam considerata) to a consideration of the soul as it acts through the bodies of animals, which means ultimately to a consideration of the natures of animals, (considerationem de animalium naturis). Since one aspect of the nature of animals is their capacity to sense, sense perception appears as an important topic for discussion throughout these shorter works, with the major treatment being found in the two treatises devoted specifically to sensation, De sensu et sensato and De memoria et reminiscentia, and in a treatise that dealt with an unusual form of sense perception, dreaming, as discussed in De somno et vigilia. The latter work adds an important dimension to an understanding of Albert's psychology of sense perception, the role of the heart in sensing, and therefore needs to be considered briefly at this point.

Confusion over the heart's role in sense perception stemmed from yet another apparent disagreement between Aristotle and his commentators; Aristotle specifically states at several points that sense perception begins in the heart whereas most of the commentaries on his works tend to stress the importance of the brain in sensing. Albert's solution to this problem, which becomes standard in later works, eliminates this disagreement by explaining how the heart functions in perception. Just as the sun is the source of all things that are generated in the macrocosm, so too the heart is the source of all vital actions in the body, and like the sun, which is active through light, the heart too has its vehicle, which is called spirit. The spirit that arises in the heart, from its heat, flows and reflows through the body, changing in subtlety in the process and motivating the vital actions of the body, such as sense perception. In the brain, spirit "perfects the animal powers, which are to sense, to imagine, and to under-stand" (perficit in cerebo virtutes animales, quae sunt sentire, imaginare, et cogitare). From here they flow to the organs of the external senses, where seeing, hearing, and the like are carried out. Accordingly, both opinions are in a way correct; the spirit that activates sense perception arises in the heart but is perfected in the brain.

Given this general description of the origin of perception, the reason for the senses ceasing to be active in sleep follows with little difficulty. During sleep the spirit that activates the senses and causes them to sense is withdrawn (somnus autem est retractio spiritus ab exterioribus organis). This withdrawal renders the senses ineffective (impotentia earum ad agendum), thus explaining why in sleep we are not aware of external stimuli. However, when the animal spirit is withdrawn from the external senses a different type of perception occurs, the sense perception of dreams.

Dreams arise from the mixing and mingling of the images stored in the brain through the action of the vapors that arise during sleep. Such mixing does not take place during the day because the images received from the external senses tend to dominate any internal mixing that may take place. But when these external images are no longer present, due to the withdrawal of the animal spirit during sleep, the internal mixing of forms takes over and produces the images that we see in sleep. Exactly how this happens and the causes of various types of dreams are topics that were of great interest to Albert, as is clear from the discussion in De somno and even more in the lengthy treatment of this subject in the Summa. This sidelight to sense perception forms an interesting chapter in the history of medieval psychology that is well worth a detailed study, especially in relation to developments in physiology and anatomy. Unfortunately, to date very little has been written along these lines.

iii De animalibus

The physiological and anatomical background to Albert's theory of dreams as well as to his entire psychology of sense perception is treated most fully in De animalibus. In this mammoth work, which ranges broadly over human and animal anatomy and physiology, he broaches the issue of sense perception on numerous occasions. Most frequently the resulting discussions focus on anatomy and provide descriptions, sometimes in very careful detail, of a particular sense or some aspect of the sensitive process. Less frequently he engaged in speculations on the relative role or placement of the senses in humans and animals or on some other comparative topic. In sum these discussions add very little to an understanding of Albert's psychology of sense perception. Very seldom does he attempt in De animalibus to explain the origin of any but the most obvious apprehensive processes. His goal in this work is not to explain what the senses know but rather how they know.

The anatomy and physiology of sense perception set out in De animalibus clearly reaffirms Albert's belief that sensation begins in the heart. The nerves of the body, which some physicians (secundum multos medicos) suggest come from the brain, have their place of origin in the heart and are only divided at the brain and base of the neck (a corde oriantur, et a cerebro et a nucha dividantur). Even the brain's location is dependent on the heart; since the heart is in the front of the body, the brain, which requires blood for perception, is also located in the front part of the body (cor … est in anteriori corporis, et ideo etiam cerebrum). Therefore, it can be argued that sensation begins when the warm vapors and animal spirit of the heart rise, like water vapors in the macrocosm, to the brain where they enliven the sensitive process (spiritus enim venit corde ad cerebrum, et digeritur ibi ad operationes animales) and are cooled. (Cooling at this point is not simply an adventitious action, it is a necessary one. If the warmth of the heart were never overcome, animals would never sleep and, of perhaps even greater consequence, the constant flow of heat from the heart into the external senses would eventually destroy them [fluerent ex ipso humores calidi in oculos et aures et oh factum, et destruerentur operationes organorum.]) In brief, then, sense perception rests on the same basic heating, cooling, moistening, drying, and enlivening actions that the physicians of this period, working in the Galenic tradition, used to account for the rest of the body's actions.

The loci within which this array of physiological activities are carried out comprise the organs of sense perception. Once at the brain, the spirit that arises in the heart passes through the complex cerebral, neural, and sense anatomy of the body to those places where perception actually takes place. Ultimately, then, it is in the organs of sense perception that body and soul join together and render those who possess the attributes of animals capable of receiving and responding to external stimuli. It is in the organs of perception that the universal principles that lie behind sense perception, the principles of animal soul and animal spirit, are shaped and formed by the substance of the body into the various forms of sense cognition that are classified under the activities of the external and internal senses. As a consequence, at this most basic level, sense perception falls squarely within the Aristotelian metaphysics of form-matter composition and Albert's task, as a medieval psychologist, has been to determine how the form of the animal soul is active through the body. This in essence, and as was stated at the beginning of this [essay], comprises the psychology of sense perception in the Middle Ages.

C. MISCELLANEOUS REFERENCES AND CONCLUSIONS

Having placed Albert's psychology of sense perception squarely into its Aristotelian framework, it should be pointed out that it is not, in my opinion, this frame-work as such that separates his science from its modern counterpart. The assumption is too often made by historians of science who are not familiar with medieval science that Aristotelian science is synonymous with a preoccupation with final causes and that it is only when this "incorrect" focus is overturned that modern science emerges. A moment's reflection on Albert's psychology of sense perception quickly indicates the fallacy of this assumption. Throughout his writings on the senses Albert is concerned primarily with material and efficient causality. It could not be otherwise within a psychology of the senses that stresses the role of the body in shaping and directing the activities of the soul. Albert's scientific explanations do not rest on final causes. At the most he could be accused of allowing too many issues to be explained in terms of formal causes, but even this criticism misses the point. The search for formal causes, in Aristotelian science, means the search for the most fundamental characteristics of things—their propensity or nature to act in certain ways—which is akin to, although certainly not in any way as sophisticated as, the modern search for the fundamental properties of matter. As a consequence, it is incorrect to look to the Aristotelian framework of Albert's psychology of sense perception per se as the ingredient that sets him apart from today's thinking on the same subject. Rather, it is the values that he holds as a scientist that are so alien to our present way of thinking, values that are apparent if one turns to Albert's views on sense perception advanced outside the context of his strictly scientific works.

Albert's fascination with sense perception clearly extended beyond the technical context of his commentaries and summae. Just as mention of the ten men in Zacharia provided a ready excuse to once again remind his audience that ten is also the number of the senses, so too mention of the ten maidens in Matthew 25:1 prompted a similar enumeration, this time with a more detailed description of some of their actions:

The philosophers assume that there are five internal senses: common sense, which compounds that which is sensed; imagination, which retains and brings back an image in the absence of its object; estimation, which draws forth friendliness and hostility, compatibility and incompatibility to itself from the sensibles; phantasy, which composes and divides that which is drawn forth [by estimation]; and memory, which preserves everything, as in a repository.

Similar partial listings can be found in the commentaries on the Sentences and on Dionysius' De coelesti hierarchia. There can be little doubt that Albert's world view contained as part of its working vocabulary the psychology of sense perception set out in the Summa and elaborated in his many later works.

Within the context of such digressions in works not directly on natural philosophy Albert continued to explain and clarify the more subtle points associated with sense perception. Confusion over Augustine's use of the term memory in De trinitate, which use seemed to contradict Avicenna's and Algazel's distinction of memory from imagination, prompts Albert to comment that Augustine was speaking only generally when he noted that memory retains corporeal images and that he did not intend to address himself to a more subtle distinction of powers. In the Liber topicorum, judgment regarding truth and error (rectitudo et peccatum) is assigned to the common sense, "which composes and divides designated particulars, and by composing and dividing it judges concerning them through the mingling action of the estimative power. Mention of the doubt of the Apostle Thomas in John 24:25 prompts Albert to suggest that Thomas was seeking first the simple verification of vision, then, since vision can deceive, the reassurance of information gained through the touch of a finger, and finally, to reassure himself that the touch of this single finger was not deceived, the infalliable experience (simul infallibile nuntient tactus experimentum) of all the fingers. Again, the conclusion is reached that his Aristotelian understanding of sense perception formed a working part of his world view.

However, as important as this understanding was to Albert and despite the amount of time he spent discussing sense perception, his scientific sensitivities in this area of investigation fall far short of being in any way equivalent or even preparatory to later and more modern developments in psychology. To a certain extent this is perhaps obvious. The simplified description of the senses that he received from his predecessors missed the mark on so many points that it is difficult to imagine how it could ever have evolved into our modern description. But it is not at this level that I would set Albert apart nor would I agree that his basic approach to the study of sense perception is particularly "unscientific." Certainly wherever possible he resorts to experience and he is profoundly interested in the physical processes that underlie cognition.

Accordingly, it is not his science of sense perception that is so alien to us as moderns as it is the importance he assigns to this science and the fruits he would expect to derive from an exhaustive study of how the senses function.

Albert believes, in harmony with the Aristotelian tradition of his day, that knowledge begins with the senses. It is objects that lie outside the soul that lead to scientia (res extra animam existentes sint causa nostrae scientiae). But just because the senses are necessary to the intellect it does not follow that the senses themselves attain much knowledge nor is there much pleasure to be gained through the senses alone. In fact, just the opposite is true. Since the purity of a sense, and hence its capacity to give pleasure, is directly proportional to its remoteness from matter (purior… sensus est remotior a materia) and since in the order of abstraction the external senses are the most closely joined to matter, followed by the internal senses, and then the mind, which is the most remote from matter, it follows that there is much more pleasure to be gained from the activities of the mind than from the activities of the senses. Moreover, it is only insofar as the senses are directed by the mind that Albert finds any real dignity in their actions. When faced with the problem of the frailty of the senses in humans, he makes no effort to defend their strength as senses per se, vis-a-vis animals. Since the quality of a sense depends on its organ, if animals have better sense organs they can sense better; dogs have superior senses of smell, wolves and wild boar better hearing, geese better vision. For Albert, the only essential superiority found in the senses of human beings as such is derived from their immediate and proper ordination to reason (secundum quod coniungitur rationi, et in illa excedit). Just as matter is ordained to form as to its final cause, so man's senses are ordered to reason, and thereby derive all their nobility and perfection.