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The (sensus communis, koinē aisthēsis)


By David Howes

The notion of the common sense was coined by the Greek philosopher, Aristotle. It has a highly intricate history. The modern idea of consciousness was quite foreign to Aristotle and his contemporaries; he spoke instead in terms of sentience. According to Aristotle, all living beings (including plants) have a nutritive soul, animals and humans share a sensitive soul, and humans alone possess a rational soul. It is the sentient powers of the sensuous soul which concern us here.


Aristotle held that every act of perception involves the “alteration” of one or more of the five sense organs by some object through the medium which conjoins them. (The trinity of organ, object, medium is integral to Aristotle’s account of perception.) The objects of perception are not things as such but provinces of sensation.  The province or “proper object” of vision is color, that of hearing is sound, that of smell is odor, that of taste is flavor. (The complexities of touch made it less amenable to such schematization, however much Aristotle tried to treat it as a unity.) Within each province — and exclusively within each province, it must be stressed — sensation takes the form of “a kind of mean” between the two extremes of the pair of contraries proper to that province: sight between white and black, hearing between shrill and dull, and so on (with the province of touch left somewhat vague due to its complexity). The implication is that we perceive by means of differences, without positive things.  Each province of sensation has its own spectrum or ratio of sensible differences, defined as that which cannot be perceived by any other sense.


This theory of the sensory functions of the soul is very neat, and very complete, but its provinciality (or exclusivity) also proved problematic. What of those objects, such as figure, number, motion, etc., known as the “common sensibles,” which are perceived by more than one sense (for example, figure is perceived by vision and by touch)? What of complex sensations (such as the experience of eating grapes, which are both red and sweet)?  How is it that we perceive that we see and hear, if a sense cannot perceive itself? Aristotle reasoned that there must be yet another sense, a shared sense, responsible for unifying, distinguishing and coordinating the five senses and their deliverances. This power of the sensuous soul he called “the common sense” (koinē aisthēsis, or sensus communis in Latin translation). For Aristotle, “this ‘sense’ constitutes a power of perception that is common to all the five senses yet reducible to none of them” (Heller Roazen 2007: 35).  Could the common senses be the sixth sense, then? Apparently not, for:


Strictly speaking, the common sense [on account of its commonality and irreducibility] is … not a sixth sense, …  it is nothing other than the sense of the difference and unity of the five senses, as a whole: the perception of the simultaneous conjunction and disjunction of sensations in the common sensible, the complex sensation, and finally, the self-reflexive perception [or, sense of sensing] (Heller-Roazen 2008: 35).


The idea of the common sense was pregnant with significance, all kinds of significance, which it took many thinkers over many centuries to spell out. All this thinking is lost on most of us today, though. For us, common sense means, simply, common sense (practical judgement), and has nothing to do with sentience. Tracing the successive elaboration and gradual dismemberment of the sensus communis would take a whole book, and indeed has: Daniel Heller-Roazen’s book, The Inner Touch: Archaeology of a Sensation provides a marvellous history of this construct. But even that monumental treatise has its lacuna. In essence, the common sense is — or, rather, was — the relational sense par excellence, the ratio of ratios, the medium of media. The last modern thinker to understand this was Marshall McLuhan. Unfortunately, since McLuhan’s writings are no less elliptical than Aristotle’s, they do not provide much guidance, and we are forced to rely on our own wits to proceed, while depending heavily on Heller-Roazen.


If we wished to visualize the relations between the common sense and the five senses, one possible image is that of the “Wheel of the Senses” in the wall-painting at Longthorpe Tower, Peterborough, which dates from the mid-fourteenth century (for a discsee illustration 6 in Woolgar 2006: 27). The painting depicts a wheel with five beasts representing the five senses positioned at the end of each of its spokes: the cock stands for sight; the boar for hearing; the vulture for smell, the monkey for taste; and, a spider in its web for touch. A king is shown behind the wheel, with his hand resting on one of its spokes. The king, who is emblematic of the common sense, exercises his dominion (and judgment) over the beasts, the senses. In another image, put forward by the great Persian philosopher of the early eleventh century, Avicenna, the relation is expressed thusly: “This power which is called the common sense is the center from which the senses ramify, and to which the senses return, like rays; and it is in truth that which senses” (quoted in Heller-Roazen 2007: 42). It must be emphasized that both of these images are overstatements of Aristotle’s notion of the common sense, as we shall see presently.


When modern thinkers criticize Aristotle for the dogmatism of his assertion that “There is no sixth sense in addition to the five enumerated – sight, hearing, smell, taste, touch,” and for his hierarchical ranking of the senses with vision at the apex, they are forgetting that he was also the inventor of the common sense, and that he did not just privilege vision (unlike, for example, Plato). It is true that he dubbed sight “the most informative of the senses.” But what to make of how he treated hearing as essential to reasoning, or of his declaration that “the well-developed sense of touch is the condition of man’s intelligence” (see Vinge 1975)? One could say that  he distributed (different) laurels to each of the senses, as any wise ruler would.


The psychologization of the common sense has a particularly convoluted history due to the liminality of its position at the interface of the five senses, and at the interface of the corporeal and the incorporeal, or sensual and rational soul. In origin, it was not the king of the senses, as in the medieval elaboration (the wall-painting at Longthorpe Tower) mentioned earlier, but rather primus inter pares, or “first among equals.” It was also largely on a par with the other three functions of the sensuous soul identified by Aristotle: imagination, the cogitative function, and memory. Being situated on the boundary of the five senses, and the boundary of the sensuous and rational soul, the common sense was a two-faced faculty. But it did not remain in this liminal position for long due to a couple of incidental observations by its author, which inflected the whole subsequent history of its elaboration (and eventual dismemberment). For an account of these observations and how they played out in the subsequent history of this enigmatic (and now forgotten) human faculty see the Introduction to The Sixth Sense Reader