This book is a detailed study of Aristotle's use of terms for a common or central sense faculty and a carefully constructed interpretation of the common sense on Aristotle's account. On Gregoric's interpretation, the common sense is a function of the perceptual capacity of the soul, which is itself a conceptual part of the sensory capacity of the soul, which is a conceptual part of the cognitive faculty of the soul. Much is right about ascribing a picture of embedded cognitive capacities to Aristotle. But whether Aristotle's notion of the common sense should be restricted to higher order perceptual functions, as Gregoric recommends, is more controversial.
Gregoric builds the argument for his interpretation step by step. His approach is remarkably systematic and thorough. The book has three parts made up of fifteen chapters. Many of the chapters concentrate on a single Aristotelian text. The first part provides an overview of the cognitive capacity of the soul and the relation between the perceptual and sensory capacity. It presents the conceptual framework in which Gregoric develops his account of the common sense. The second part provides a detailed analysis of Aristotelian texts that might plausibly be construed as making reference to the common sense. The third part describes the four functions that Gregoric assigns the common sense and argues against the inclusion of two other functions that are frequently ascribed to the common sense. The concluding chapter summarizes the argument of the preceding fifteen chapters.
In Part I Gregoric presents and defends a particular way of understanding and labeling the cognitive faculties of the soul. Appealing to a quick survey of De Anima II and III, he argues that the soul allows only for conceptual division and that the perceptual capacity of the soul is divisible into the individual senses. The latter point is then developed in further detail. He then looks at the account of sense organs in the De Anima, De Partibus Animalium and elsewhere in the corpus. A picture of the conceptual parts of the soul emerges that is based on these texts. Gregoric distinguishes, on Aristotle's behalf, between the perceptual capacity and the imaginative capacity of the soul; because neither of these faculties is a conceptual part of the other, he posits a capacity that contains both of these capacities as its conceptual parts, viz. the sensory capacity. This picture of the sensory capacity of the soul is appealed to throughout. Despite its importance, it is not defended in the first part of the book, nor is it ever defended as a whole. It provides the framework in which Gregoric interprets specific references to a common sense.
Part II examines texts in which the term 'common sense' occurs. It begins with a chapter entitled "Overlooked Occurrences of the Phrase 'Common Sense'." In Historia Animalium I.3, Aristotle remarks that the sense of touch is common to all animals. Gregoric argues that this is a reference to the common sense and on this basis he concludes that each of the five senses is a common sense (66). He also finds this picture of the individual senses as common senses in Metaphysics I.1. Aristotle argues that there is no special sense for the common sensibles in De Anima III.1 425a14-29. Gregoric argues against what he calls the standard interpretation of this passage, viz. the view that Aristotle posits a higher order perceptual power acting through the individual senses, and he offers an alternative interpretation. "Instead of a special sense for the common perceptibles, we have a common sense, that is any one of the common senses" (76).
The next passage to be examined is found in De Partibus Animalium IV.10. Aristotle links our erect posture with our intelligence and explains that in other creatures there is pressure on the common sense and the intellect (διάνοια) making them less mobile (686a27-35). In this context, unlike the passages considered in the preceding two chapters, Gregoric believes that the term 'common sense' refers to the sensory capacity of the soul that includes both the perceptual and the imaginative capacities. An examination of Aristotle's use of this term in De Memoria et Reminiscentia 1 yields the same picture--that of a sensory capacity made up of the capacities for perception and imagination. In De Memoria 1 Aristotle argues that memory belongs to the primary perceptual capacity of the soul (πρῶτον αἰσθητικόν) on the grounds that time is grasped by the faculty that apprehends change and magnitude. Gregoric rejects 'the standard interpretation' that makes time a common perceptible; he then argues that a sensory capacity is required for grasping the temporal relation in memory that is a more general capacity than either the perceptual capacity or the imaginative capacity.
Turning to De Anima III.7, Gregoric addresses the question whether the dative of 'common' (κοινῇ) at 431b5 is an elliptical occurrence of 'common sense.' Here Aristotle is explaining how we interpret a moving beacon as a signal of danger. He suggests that it is 'by the common'. Some commentators have urged the emendation of the text to avoid the implication that the faculty involved is the common sense. Gregoric grants that we might be well advised to follow this suggestion but that if the text is kept as received, κοινῇ should be read as a reference to the general sensory capacity. In a short concluding chapter, Gregoric summarizes his findings in Part II. The term 'common sense' has three different uses in Aristotle. (1) It serves as a context-dependent description of specific senses; (2) it describes a certain sensibility of the individual senses to particular features of the world; and (3) it is the proper name for the sensory capacity of the soul that is made up of the perceptual and imaginative capacities.
In Part III, Gregoric develops a notion of 'common sense' that does not coincide with any of the three uses of the phrase identified in Part II. It emphasizes higher order perceptual functions that go beyond the individual senses. More precisely, the topic is the higher order perceptual power that emerges from the unity of the perceptual capacity but is independent of imagination. Aristotle assigns the simultaneous perception of two distinct special senses to the perceptual faculty for all perceptibles (αἰσθητικὸν πάντων) in De Sensu 7. Gregoric takes the reader through Aristotle's argument line by line and with great sensitivity explains the background aporia that drives Aristotle's analysis. He reminds us that (on his interpretation) "when the perceptual part of the soul operates as a single thing ... we are talking about the higher-order perceptual power that goes by the name 'common sense" (138). Having presented Aristotle's solution to the problem of the cross-modal binding of heterogeneous perceptibles such as white and sweet, Gregoric turns to the simultaneous perception of homogeneous perceptibles, e.g. white and blue. He claims that for Aristotle it is impossible to see more than one color at a time even though it is possible to perceive two distinct colors simultaneously. He bases this claim on Aristotle's remark at De Sensu 449a16-19 that the perceptual capacity for all objects is sometimes different in kind (γένει) and sometimes different in species (εἴδει).
Continuing on the topic of simultaneous perception, in the next chapter Gregoric considers Aristotle's account of perceptual discrimination in De Anima III.2. Here too Aristotle raises the question of which faculty perceives the difference between white and sweet. However, in presenting his argument, he also mentions the homogeneous perceptibles white and black and denies that the same thing can be both simultaneously. As interpreted by Gregoric, this remark rules out sight as the discriminating faculty in the case of an object that is white and black in different parts. If we accept this reading, then De Anima III.2 not only assigns the discrimination of heterogeneous perceptibles to a higher perceptual power but it also assigns the simultaneous perception of homogeneous perceptibles to the common sense rather than the individual senses. Aristotle compares the discriminating faculty (τὸ κρῖνον) to a point, which is both indivisible as one point and divisible when conceived as two (427a9-14). This is a difficult text to interpret. The argument is compressed and the import of the analogy with a point is uncertain. Commentators have disagreed about whether Aristotle has in mind the point conceived as the point which divides a line or conceived as the point at the center of a circle. The assumption that we need to choose between these two views is mistaken. Because the point may be conceived in both ways, Gregoric argues, it is an apt analogue for a faculty that "simultaneously accesses and discriminates two perceptibles" (153). This is an interesting suggestion. However, it is perhaps worth noting that both conceptions of a point are in play in the case of the center of the circle, which divides the diameter into two radii. Recognizing that assigning the simultaneous perception of two homogeneous perceptibles to the common sense will be controversial, Gregoric defends his interpretation on which the visual field, because made up of many colors, is not perceived by sight simultaneously but only color bit by color bit sequentially. He attributes to Aristotle a problematic assumption "that only one special perceptible can actualize the corresponding individual sense at a time" (156). The case for this attribution is largely internal to Gregoric's interpretation, and thus many readers may be reluctant to attribute it to Aristotle.
Turning his attention to Aristotle's explanation of sleeping in De Somno et Vigilia, Gregoric finds support for distinguishing between the perceptual and imaginative capacities of the sensory capacity of the soul and for identifying sleep with the inactivity of the higher order functions of the perceptual capacity, viz., the common sense. If sleeping is the immobilization of the common sense, then waking must be its activity. Gregoric argues that the awareness of the activity of one's senses is constitutive of being awake and that this awareness is a function of the common sense. Further evidence for this line of interpretation is found in the account of perceiving that we see and hear in De Anima III.2. This may seem surprising because Aristotle does not mention the common sense in this passage and seems to assign self-awareness to individual senses. Gregoric explains that Aristotle is addressing a puzzle raised in Plato's Charmides. Since the topic there is the individual senses, Aristotle also talks about individual senses in the De Anima instead of the central sense that is mentioned in the De Somno. Although Aristotle appears to say that the perceiving faculty is colored in the case of perceiving that we see (425b22-24), Gregoric argues that this is only for dialectical reasons and that Aristotle's considered solution is that we perceive that we see by sight but not in a way that involves color. This description would be consistent with assigning this awareness to the common sense. This is an ingenious solution to the apparent inconsistency between De Somno 2 with De Anima III.2, but not an uncontroversial one.
The final substantive chapter explains why two functions widely assigned to the common sense have not been attributed to the common sense. The first of these functions is the perception of the common perceptibles. Earlier (Part 2 Chapter 2) Gregoric had argued for a reading of De Anima III.1 that makes the common perceptibles objects of the individual senses. In order to explain why Aristotle seems to distinguish between sight's grasp of magnitude, a common sensible, and its grasp of color, Gregoric recommends that we distinguish between how the common perceptibles are perceived and how the difference between common perceptibles and special perceptibles is recognized. The latter but not the former is a function of the common sense. The other function that Gregoric, in contrast to some other interpreters, does not assign the common sense is accidental perception. Aristotle calls both the perception of accidental unities, e.g., the son of Diares, and the perception of the special object of another sense, e.g., the perception of sweet by sight, accidental. Both types, Gregoric argues, involve imagination as well as perception and hence belong not to the common sense but to the sensory capacity of the soul.
The concluding chapter begins with two questions: What does Aristotle designate with the phrase 'common sense'? What should we designate as the Aristotelian notion of the common sense? (203). The first question, largely answered in the second part of the book, is that Aristotle uses the term 'common sense' for three different things, viz. the individual senses, common sensibility to particular features, and the sensory capacity of the soul. The second question is answered by assigning the common sense only the four higher order perceptual functions discussed in the third part of the book. These are: simultaneous perception, perceptual discrimination, control of the senses and monitoring of the senses.
We would be hard pressed to find a more careful and thoughtful examination of the texts in which Aristotle use the term, κοινὴ αἴσθησις, or refers to a central perceptual power. Gregoric also displays an impressive grasp of the work of other interpreters. The picture of the common sense that emerges is that of a versatile cognitive capacity that Aristotle appeals to in explanations of a wide variety of broadly sensory phenomena. In these respects, Aristotle on the Common Sense makes a truly significant contribution to the growing body of literature on Aristotle's theory of perception. The recommendation to restrict Aristotle's notion of the common sense to a particular sort of cognitive activity will doubtless prove more controversial.
The comprehensiveness of Gregoric's approach is in tension with his desire to limit the scope of the common sense--at least insofar as we use that term to describe Aristotle's position. The tension between these two aspects of Gregoric's interpretation is evident in his account of the architecture of the sensory capacity. The sensory capacity has according to Gregoric two relatively independent parts, viz. the perceptual capacity and the imaginative capacity. There is a tension between this picture and the need to attribute to Aristotle a fully integrated picture of the sensory capacity. As Gregoric correctly notes in the case of remembering, "... Aristotle needs to assign the grasp of time to something more general than the imaginative capacity of the soul, to something capable of combining perception and imagination (107)." Aristotle assigns dreaming to the sensory capacity qua imaginative (αἰσθητικὸν ᾗ τὸ φανταστικόν) (De Ins. 1 459a21-22). We would be hard pressed to find Aristotelian terms for drawing a distinction between a perceptual and a sensory capacity. His term for both is αἰσθητικόν. What this suggests is that Gregoric is on the right track in noting that Aristotle differentiates faculties more or less narrowly depending upon which cognitive activity he is describing. Sight, for instance, is a distinct capacity defined by its own proper object, color, and its own activity, seeing. It is also an exercise of the capacity to perceive, when the object is defined more broadly as a perceptible and the activity as perceiving. Similarly, the ability to dream is a distinct capacity for a specific activity, dreaming, that can be described more broadly as an exercise of the imagination or still more broadly as an activity of the perceptual/sensory capacity of the soul. As Gregoric recognizes, Aristotle's picture is one where cognitive faculties are embedded and individual cognitive activities may be described at different levels of generality. As long as Gregoric's talk of conceptual parts and his distinction between a perceptual and a sensory capacity are construed in a way that does not reify these analytic tools, they might well prove useful. The worry remains that as presented in the book, however, the temptation to attribute a "conglomerate" picture of cognition to Aristotle will lead to misunderstanding his position.
For those of us who would prefer to take Aristotle's usage as our guide, a more compelling interpretation would be one on which the sensory capacity of the soul is the central sense faculty in which both imaginative and perceptual functions are embedded in a way that does not threaten the unity of the sensory capacity.1 Following Aristotle's lead we should be very hesitant to draw sharp distinctions where he envisages permeable boundaries as indicated by phrases such as the general perceptual faculty as imaginative.
Reservations aside, this is a truly valuable study of Aristotle's conception of the common sense. Gregoric examines all the relevant texts and probes them by asking many of the right questions; he also brings a vast body of secondary literature to bear on this task. The book will no doubt become a "must read" for serious students of Aristotle's theory of perception and cognition more generally.
1. See D. Modrak, 1987, Aristotle: The Power of Perception (Chicago) for a comprehensive treatment of the perceptual faculty of the soul.