This introduction to the cogitative power in Thomas Aquinas is divided into two parts. In Part I. we will briefly trace the historical background of the cogitative power from Aristotle to Aquinas. Part II. will outline the general doctrine of the cogitative power as it is developed by Thomas Aquinas. For the sake of parsimony, I will not repeat in Part II. most of the fundamental doctrinal issues which are taken up in Part I. The second part will only elaborate how Aquinas developed the doctrine of the cogitative power and the diverse ways in which it is integrated into his accounts of incidental sensation, memory, experience, preparation of the phantasms, abstraction from the phantasms, conversion to the phantasms, cognition and scientific knowledge of the singular, practical reasoning, the virtue of prudence, the proper object of the passions, and the unity of the virtues through prudence. In the future I hope to provide individual posts which discuss each of these points length, whereas here they will simply be introduced along with a few key loci classici.
A Brief History of the Vis Cogitativa: From Aristotle to Aquinas
§ 1. Aristotle’s Threefold Division of Sensibles
The doctrine of the vis cogitativa has its origins in the philosophical psychology of Aristotle (384–322 BC), although this does not exclude Platonic correlations. After defining the soul as the first actuality of an organic body, Aristotle moves beyond his general treatment of the subject of the science to take up vegetative and sensitive animation. By the time we get to de Anima II. 6, we are ready to distinguish the objects of sensory cognition. Aristotle distinguishes sensible reality according to his categorical distinction between the essential (per se) and the accidental (per accidens). The essential sensibles are those objects of reality which directly and through themselves, i.e., per se, act on the sense organs and are thereby cognized through our external sense faculties. The accidental or incidental sensibles are not cognized in and through our external sense faculties but are cognizable objects or features of reality which are apprehended by our higher cognitive powers, albeit, in as much as they are somehow present in the essential sensibles.
§ 2. Essential Sensibles: Proper and Common
Essential sensibles are of two different kinds, proper sensibles and common sensibles. Proper sensibles are essential sensibles which are uniquely apprehended by a single sense faculty, like color to vision, sound to audition, odor to olfaction, flavor to gustation, and tactibilia to tactility. Neither color is heard, nor sound tasted and so these objects are unique or proper essential sensibles. These proper sensibles differentiate the five sensory modalities we are familiar with. There are, however, a number of sensibles which, even though they are essentially sensed, they are themselves not unique to any one external sense faculty but are commonly sensed by at least a few of the five external senses. For instance, motion is visually seen and audibly heard, just as dimension and shape is cognized by both tactility and vision. Common sensibles like motion, dimension, magnitude, and shape are then essentially sensed by a number of different external sense powers in virtue of their proper objects. The phenomenal unity or sensible gestalt is apprehended as a given whole by the faculty Aquinas calls the sensus communis. The proper object of the sensus communis or gestalt sense is simply the per se sensible, which is the essentially sensible phenomenal unity or formally sensible whole (gestalt). It should be noted that Aristotle’s common sense (κοινή αίσθησις) receives a variety of other interpretations throughout the commentary tradition.
§ 3. Accidental Sensibles
Aristotle thinks that there is more involved in sensory cognitive experience than simply the apprehension of bare essential sensibles; we cognize more than what we see as white objects in motion. Concomitant to such sensations we also perceive objects like the son of Diares, which is accidental to these essential sensibles of white and motion. To cognize this man, is to apprehend neither a sensible, nor a universal definition, but the instantiation of the essence in the sensible substance as here and now, i.e., a primary substance. It is through incidental sensibles that animals are able to learn through sounds; not sounds as such, but incidentally, inasmuch as some sounds are meaningful or significant. Brute animals which can apprehend significant sounds and other sensibles seem to partake of opinion and prudence, that is, their higher faculties and operations resemble that of man’s lower more practical intellectual and rational capacities.
§ 4. Greek and Arabic Commentators
The Greek and Arabic commentary tradition developed further articulations of the sense faculties, especially after the numerous insights of the Greek physician Galen (129–199 AD). However, despite such developments on the inner senses, the numerous disputes about the nature of the intellect became central. Aristotle’s cryptic account of the acting intellect and the intellect which is passive like matter, became the subject of contentious debates that continue to bewilder contemporary Aristotelian scholars (cf. de Anima III. 4-5). The various descriptions Aristotle gives of these intellects in the de Anima, Posterior Analytics Metaphysics, Nicomachean Ethics, and elsewhere seem to conflict with each other. In order to resolve such difficulties many Aristotelians were led to positing further intellectual powers, the passive and corruptible intellect of de Anima III.5 is contrasted with the intellect that is impassible and yet is able to receive all things from de Anima III. 4. Many commentators identified this passible intellect with the phantasia, i.e., the sensorial power to form phantasms. This interpretation not only seems to accord with Aristotle’s account of prudence (phronesis) in Nicomachean Ethics VI, but also seems to provide a further articulation of Aristotle’s insistence that the operations of the intellect must always turn to these phantasms.
Further questions concerned how these phantasms are able to act on the intellect which is receptive of all things; what role does the acting intellect play in making these phantasms actually intelligible? The answers given to these problems are almost as diverse as the many Greek, Arabic, and Latin commentators who took up these disputes. Some interpretations understood the operations of material intellect to arise out of the bodily faculties; this view is sort of like a proto-epiphenomenalism. On this account, the material intellect is but a disposition of the sensorial phantasms that becomes an epiphenomenon by virtue of the separate immaterial agent intellect’s acting on the phantasms.
On the other extreme we have the infamous final position of Averroes (c. 1126–1198), who held that both the agent and material intellect were separate substances which were common to all individual human beings who achieve intellectual cognition through their union with these two separate intellects. Despite such diverse interpretations on the immanent or transcendent character of the possible or material intellect, most commentators held that that the agent intellect is in some way separate from man.
Nevertheless there were those who found both extremes unacceptable for the two intellects. In the middle we have doctrines which contend that both the possible and agent intellect immanent powers of the human being. This was the position of Thomas Aquinas (1224-1274), which it must be noted was an unusual interpretation of Aristotle with respect to the consensus of most commentators on the de Anima.
Aside from these central issues on the nature of the intellect, there are further problems concerning the proper division of the internal sense powers. The common sense (sensus communis) is clearly different from phantasia or imagination, because the former causes the image to be imprinted on the latter. But is phantasia, the power to form phantasms, the same as memory or different? In Aristotle’s On Memory and Reminiscence they are at least coordinated and belong to the same part of the soul. But the Parva Naturalia is not entirely clear, and only seems to add further difficulties by introducing an additional distinction between memory, reminiscence and the opinionative faculty. In other places, Aristotle also speaks of the ability to form experience (empeiria) as distinct from memory and sensation in Posterior Analytics II. 19 and Metaphysics I.1. How all these diverse powers and operations fit together were just a few of the numerous loose ends which were left to Aristotle’s commentators. This is the beginning of the historical context that led to the development of the cogitative power in medieval philosophical psychology.
§ 5. Avicenna: Intentions and the Estimative Power
The Islamic philosophical polymath Avicenna (980-1037) is credited with codifying further taxonomical principles and for his insights into the distinctive objects of the higher inner senses. Avicenna further clarified Aristotle’s notion of accidental or incidental sensibles by articulating what these objects are essentially in themselves. Avicenna calls these objections intentions (ma‘nā, intentio). He notes that a sheep is not afraid of a wolf simply because of its color or motion, but because it is a predator and something to be avoided. The object apprehended here as a predator to be avoided is not an object that is reducible to any essential sensibles; rather, to be avoided is an intention which the sheep apprehends as incidental to the per se sensibles of the wolf’s color, shape, smell, and so forth. Avicenna calls the inner sense faculty which apprehends such individual intentions the estimative (wham) faculty or the opinionative faculty (al-mutawahhimah wa-al-ẓānnah).
Avicenna also distinguishes between receptive and retentative powers. For this he develops the distinctions made in Aristotle’s On Memory and Reminiscence 1, where it is noted that that among material objects some are able to receive well but lack the capacity to retain, whereas others are proficient at retaining forms but not with receiving them. Avicenna uses this physiological basis to ground his taxonomical distinction between psychological powers which receive and those which retain. The sensus communis receives essential sensibles and the estimative receives intentions, i.e., incidental sensibles. The formative power of imagination is posited as a power which retains the essential sensibles of the sensus communis, and memory is coordinated to be the retentative power of the estimative’s intentions. Avicenna posits a fifth inner sense power which is a sort of active or compositive imagination. This is the power whereby we are able to draw upon the retained essential sensibles of the imagination and compose and divide them in novel and creative ways, such as to conjure up the image of an emerald mountain. A novel feature of this power is its ability to mediate between sensory operations and rational operations. The composite imagination is able to act simply for sensory ends, but it is also able to be brought under the direction of reason. When the compositive imagination is ordered by reason it is more properly called the cogitative power (mufakkirah) and not simply the compositive imagination. It is in Avicenna that we find for the first time an elaborate and articulated account of the taxonomy of inner senses including their operations, and their proper objects. He gives us five inner sense faculties along with a clear delineation of how they differ from each other.
- Sensus communis – receptive faculty of per se sensibles
- Imagination – retentative faculty of per se sensibles
- Estimative – receptive faculty of intentions, i.e., per accidens sensibles
- Memory – retentative faculty of intentions
- Compositive Imagination – conjuring power of per se sensibles
- Cogitative Power – when the compositive imagination is under the direction of reason
Avicenna also has some very interesting comments in his own introduction to natural philosophy. In the first book of the natural philosophy part of his Book of the Healing, Avicenna follows the general order of Aristotle’s Physics. He seems to introduce here the notion of the vague individual as a further articulation of his doctrine of intentions. It is also offered as a clarification of Aristotle’s own analogy about our knowledge in a science as it is similar to the vague knowledge of child which still lacks the proper differentiation between fathers and men. Deborah Black has a forthcoming article which addresses this notion of the vague individual in Avicenna.
§ 6. Averroes and Albert the Great
 There is a growing body of secondary literature on many of the topics addressed here. I will not be discussing any of the finer points of these historical doctrines, or the disputes found in contemporary debates. Most of the doctrines introduced here have been derived from my own research as well from the research of Mark Barker, Deborah Black, Cornelio Fabro, Anthony Lisska, George Klubertanz S.J., Richard Taylor, and Harry Wolfson.
 For more detailed historical accounts see, Deborah Black, “Imagination and Estimation: Arabic Paradigms and Latin Transformations,” Topoi 19 (2000): 59-75; Harry Austryn Wolfson, “The Internal Senses in Latin, Arabic, and Hebrew Philosophical texts.” Harvard Theological Review, (1935): 69-133.
 Cf. Aristotle, de Anima II. 1-2.
 N.b. Aquinas explicitly rejects the position that the proper object of the sensus communis is the common sensibles. Aquinas refers to its proper object as the sensible, simpliciter.
 “We speak of an incidental object of sense where e.g. the white object which we see is the son of Diares; here because being the son of Diares is incidental to the white which is perceived, we speak of the son of Diares as being incidentally perceived. That is why it in no way as such affects the senses. Of the things perceptible in themselves, the special objects are properly called perceptible and it is to them that in the nature of things the structure of each several sense is adapted.” Aristotle, de Anima II. 6 418a20-25. (trans. J.A. Smith) in The Complete Works of Aristotle, (The Revised Oxford Translation) Jonathan Barnes, ed. (Princeton: Princeton University Press, 1984).
 Cf. De Sensu 1, 437a4-16 and Metaphysics I.1.
 In addition to the paradigmatic treatment in Aristotle, de Anima II. 6, 418a8-a25 see also the following implicit and explicit references to this doctrine: Peri Hermeneias 1, 16a2-9; 2, 16a19-30. Prior Analytics I 27, 43a25-36. Posterior Analytics II. 19, 100a15-b5ff. de Anima II. 8, 420b5-23; III 1,425a14 ff.; 3, 428b18-26; 6, 430b26-30; 7, 431b2-10. De Sensu 1, 437a4-16. On Dreams 1, 458b3-16; Metaphysics I 1, 980a22-b15. Nicomachean Ethics, II 9, 1109b20-23; VI 8, 1142a23-30; VII 3, 1147a24-b5. Cf. Paolo C. Biondi, Aristotle Posterior Analytics II. 19: Introduction, Greek Text, Translation and Commentary: Accompanied by a Critical Analysis (Saint-Nicolas Québec: Les Presses de l’ Université Laval, 2004). Stanford Cashdollar, “Aristotle’s Account of Incidental Perception,” Phronesis 18 (1973): 156-175. Joseph Owens, “Aristotle on Common Sensibles and Incidental Perception” Phoenix, Vol. 36, No. 3 (1982): 215-236.
 This intellect was later referred to as the material and possible intellect in contrast to the passive intellect. Cf. Alexander of Aphrodisias, de Anima, 81.
 Cf. Aristotle, de Anima, III.7, 431a15-16.
 Cf. On Memory 1, 450a20-25.
 “If, then, the exercise of the faculty of sight is seeing, that of the auditory faculty, hearing, and, in general that of the faculty of sense-perception, perceiving; and if there are some perceptions common to the senses, such as figure, magnitude, motion, &c., while there are others, as colour, sound, taste, which are special; and further, if all creatures, when the eyes are closed in sleep, are unable to see, and the analogous statement is true of the other senses, it is clear that we perceive nothing when asleep; we may conclude that it is not by sense-perception we perceive a dream. But neither is it by opinion that we do so. For we not only assert, e.g., that some object approaching is a man or a horse, but that the object is white or beautiful, points on which opinion without sense-perception would say nothing either truly or falsely. It is, however, a fact that the soul makes such assertions in sleep. We seem to see equally well that the approaching figure is a man, and that it is white.” Aristotle, On Dreams I 458b3-14. Cf. de Anima III. 2-3; de Memoria I-II; & Nicomachean Ethics VI.
 Cf. Avicenna, Treatise on the Soul, ch. 6 (L358.17-361.3/A168-9).
 Cf. Aristotle, de Memoria 1, 450a26-b10.
 Cf. Avicenna, Shifā’: de Anima, 6.1.2: 1.5, 4.1.