Embodying genre: from Galton’s generic faces to Peirce’s embodied ideas

1 Francis Galton: the universal and the ghost of the singular

Francis Galton’s conception of “composite photograph” is disorienting if you have in mind Barthes’ words about photography, about the “impossible science of unique being,” if you have in mind all the faces that appear and the face that does not appear in Camera Lucida.

In the late 1870s, Galton put into practice and described the technique of “composite photography.” This technique consists in overlapping several images of faces on the same photographic plate. In the image resulting from this operation, the common features, repeatedly superimposed, are highlighted. On the other hand, the singular characteristics, imprinted only once, tend to be diluted until they disappear. The aim of this procedure is the passage from the image of the singular to what Galton calls the “generic image.” Galton writes: “The word ‘generic’ presupposes a genus, that is to say, a collection of individuals who have much in common, and among whom medium characteristics are very much more frequent than extreme ones” (Galton 1879: 162). Thus, Galton defines “genus” very classically, as a set in which many elements are grouped for their similarity. The technique elaborated by Galton aims to erase the singular traits, the “extreme” traits, the traits that recur in a single face and, at the same time, aims to highlight the most frequent, “average” and common traits. Galton believed he could make the genus come into presence through this procedure. The composite photographs are a technical expedient that allow the genus to manifest itself “in flesh and bones,” compensating for the human mind’s inability to intuit the general. Generic photography makes it possible to “see” the general, that is, intuit by the senses what the human mind cannot intuit intellectually. In the generic image, the face loses all expressions and becomes measurable physicality, excarnated to the point where Galton conceived of applying this technique directly to skulls. Through the methodology of composite photography, Galton responded “technically” to the age-old problem of the reality of universals. According to Galton, composite photography supplants the human mind’s defective perception of the genre, because it brings universals into presence, thus showing us their reality. Galton defines composite photographs as “real generalizations” because they compare the singularities making the result of this comparison directly visible by the generic image (Galton 1879: 166).

Galton applies the technique of composite photography to faces. Barthes in Camera Lucida shows that the photographs of the human face differ from photographs of any other subject. This difference has to do with a double manifestation of singularity: the photograph of the face, on the one hand, catches and stops the exceptionality of the “here and now” and, on the other hand, it catches the absolute singularity of the human face in its expressivity, indecomposability, and irreplaceability, making appear what Barthes calls “air” that is “that exorbitant thing which induces from body to soul” (Barthes 2010: 109).

The operation attempted by Galton is diametrically opposed to the one that Barthes attempts a hundred years later: while Barthes tries to highlight the overbearing emergence of the singular in the photographs of the human face, Galton seeks, on the contrary, to reduce, to put out of play, this exorbitant and intractable singularity, to confine it on the margins of that ordinary regularity that “genre” defines. As Davie (2003: 198) explains, Galton invented composite photography as a methodology to examine a large number of criminals held in English prisons in order to identify the general traits of the “average criminal,” that is to say, the “biotype” of the criminal. Galton would later apply this technique to produce the generic image of the face of the sick, of people belonging to the same family, of the same person at various stages of his or her life, and to the physical classification of human “races,” with an alarming insistence on the type of the “Jew.” The composite photography aims to recognize human “genres” by visualizing shared biological and hereditary facial characteristics. For this reason, it is deeply connected with the general context of Galton’s research and, in particular, with his foundation of “eugenics.” In Composed portraits (1878), Galton explicitly affirms that the technique of composite photography can be helpful for the identification of the different human “races” because it highlights the hereditarily transmitted traits. In the early years of the twentieth century, Galton expands the use of composite photography, founding “analytical photography,” a method that measures the distance of each singular face from the generic face. The measurement scale used by analytical photography is far from being neutral, since the more a face is distant from the model, the more it is considered deviated and defected (Galton 1900).

In his early theoretical writings on composite photography, Galton, in addition to these “eugenic” uses, highlights two others uses of generic images, one of an “artistic” nature and the other of a “psychological” nature.

Galton describes photography as a defective tool compared to pictorial representation. This defect consists of reproducing one of its expressions instead of representing a face in its essence. Composite photography overcomes this limitation, making photography a better representation tool than pictorial representation. Indeed, composite photography holds together, even more precisely than a painter’s mind does, all the images of a face, highlighting the persistence of genre and erasing the fortuity and the transitoriness of the singularity. In the context of this “artistic” use, Galton refers primarily to the composition of various images of the face of the same person at different times of his life. The generic image produced by composite photography, in this case, makes appear “the essential” by identifying someone’s resemblance to himself, that is, by identifying what persists when expressions, attitudes, ages, situations, and contexts change. Composite photography highlights the essential by erasing what happens, changes, or vanishes. In this way, composite photography mechanically makes up for the structural imperfection of what Galton calls the “pictorial imagination,” which is the capacity of the human mind to memorize visual images and to detect, through a mechanism of overlapping, their regularities and common features in order to connect many singularities in one genre:

A composite portrait represents the picture that would rise before the mind’s eye of a man who had the gift of pictorial imagination in an exalted degree. But the imaginative power even of the highest artists is far from precise, and is so apt to be biased by special cases that may have struck their fancies, that no two artists agree in any of their typical forms. The merit of the photographic composite is its mechanical precision, being subject to no errors beyond those incidental to photographic production. (Galton 1879a: 132)

Even those endowed to the highest degree with the gift of “pictorial imagination,” therefore, are subject to the distraction of the particular that prevents them from capturing the general form. Galton describes the imperfection of the human mind in the production of generic images as inherent and structural and therefore not surmountable or perfectible. In this sense, Galton indicates a “psychological” use of the method of composite photography (1879a: 161), which is capable of simulating and perfecting the mechanism by which the human mind produces general ideas by eliminating the possibility of error in the transition from the singular to the general: “A generic mental image may be considered to be nothing more than a generic portrait stamped on the brain by the successive impressions made by its component images” (Galton 1879a: 161–162).

In Generic images (1879), Galton analyzes the way our minds form general images by asking why these general mental images are very often sources of confusion and error. According to Galton, composite photography, technically reproducing this mechanism of moving from the singular to the general, helps to bring order to the mental process of constituting the general by identifying its limits and preventing its errors. Galton links these limits to the tendency to be attracted and distracted by the unusual, the new, and the exceptional. If we allow the same portrait to be imprinted fifty times in a row on the same photographic plate, it will emerge with greater force than the portrait that is allowed to be imprinted on the same plate only once. However, in the case of the human mind, this process works differently. What strikes our mind is the unusual, the exceptional occurrence, the difference. Furthermore, according to Galton, it is precisely in this tendency to be attracted, like children or savages, by the strange and the extraordinary that lies the source of the errors determined by generic mental images (Galton 1879: 166).

The tendency to give importance to what is extraordinary is thus the defect of the human mind that the mechanical device of composite photography corrects, putting the emphasis back on the homogeneous, the resembling, the average, the common, and converting the expressive exceptionality of the face in the stable regularity of the generic image. Unlike the generic mental image, the photographic generic image highlights, with mechanical precision, the features of homogeneity. The manifestation of this homogeneity is, for Galton, the overlapping of the contours and physical features of faces. Where there is a sharp image, there is homogeneity because the features overlap; where there is a blur, there is inhomogeneity because the features do not line up.

In 1879, to explain this relationship between homogeneous with sharp and inhomogeneous with blurred, Galton gives the example of the overlapping of the faces of three brothers, one woman, and two men. Illustrating this case, case Galton argues that there is a substantial homogeneity from the point of view of genetic familiarity, which determines the similarity of the physical conformation of the faces (and thus their precise overlap), and a weaker and negligible heterogeneity, which is constituted by sexual difference. Indeed, the generic image of the three brothers marks the common features of familiarity within a face that is “neither male nor female” (Galton 1879: 163). In Galton’s words, the sexual difference disappears in the generic image of the three brothers. On the other hand, however, gender appears like a ghost in the blur determined by the different hairstyles and clothes of the three brothers, as if it were more persistent than biological sexual traits: “Ghosts of portions of male and female attire, due to those peculiarities of the separate portraits, are seen about and around the composite, but they are not sufficiently vivid to distract the attention” (Galton 1879: 163). Interestingly, Galton uses this word “ghost,” to which the singular is connected. This “ghost” is the reemergence of the singular in the form of the blur, that is the invisible becoming visible. On the one hand, the “genus,” the general, the universal, therefore, is connected by Galton to sharpness, to distinction; on the other hand, the singular is connected to blurriness, to that which is not sharp, to the visualization of what is not visible and which is nothing but an accident, an undesirable, a “ghostly accessory,” Galton says. This “ghostly accessory” measures the tendency of individuals to “deviate from the central type” (Galton 1879: 166).

These ghosts besiege the generic image on its margins. Galton exorcises these ghosts (without being able to make them disappear) by asserting that the more homogeneous images are overlapped, the more these ghostly blurs tend to disappear from the photographic plate because as the overlaps increase, on the one hand, the features marked several times appear more and more vivid and, on the other hand, those marked only once tend to disappear. This disappearance, this marginality of the ghostly element on which Galton insists so much is, as Sekula notes, constantly belied by the same composite images he produces and shows since the blurring within these images is by no means relegated to the margins and never disappears but, on the contrary, is persistent and invades the photograph even in its central part (Sekula 1986: 48). Galton does not see (or does not want to see) this invasion and argues that blurring tends to fade away in composite photographs because the ordinary appears more prominent. While nonhomogeneous images disappear in composite photography, in the human mind, they persist. For this reason, according to Galton, generic mental images are very often vitiated by the presence of nonhomogeneous singular images that give rise to “monstrous compositions” (Galton 1879: 166). This intrusion of the exceptional and the extraordinary, this abusive force of what is weak, makes our mental images blurry: where generic images have a slight blurring in the outline, in mental images, this blurring becomes more critical, not marginal, confusing the sharpness of the outlines which, Galton says, “crowd in weak and incongruous images” (Galton 1879: 169). Galton writes:

The human mind is, therefore, a most imperfect apparatus for the elaboration of general ideas. Compared with those of brutes its powers are marvellous, but for all that they fall vastly short of perfection. The criterion of a perfect mind would lie in its capacity of always creating images of a truly generic kind, deduced from the whole range of its past experiences. (Galton 1879: 169).

Whether used for eugenic, artistic or psychological purposes, the result of composite photography is the technical production of no one’s face, of a faceless face, an incarnation without existence. The generic representation is an “ideal face” (Galton 1881: 145), that is, a face with no age, with no location or background, with no expression, with no shadows, with no gender or sex, with no makeup, with no wrinkles, with anything but persistent hereditary biological characters. Even when the images of the same person are overlapped at different stages of their life, the generic representation is a face that never existed, the face of how someone never was. The genre manifests itself by embodying itself in the face of no one. What makes Galton’s operation quite remarkable is that the technique of composite photography manifests the genre in an “embodied” form, incarnating it as a “face,” that is, in the guise of that “sui generis” which maximally denies it.

The generic image is the genre in flesh and bones, and these bones are those of the human skull. By embodying genre in a faceless face, composite photography seeks to eliminate the two elements that Barthes emphasizes in his analysis of photography, namely, on the one hand, that disturbing ghostly essence of photography constituted by the return of a past and, on the other hand, the irreducible singularity of the human face that expresses itself through its “air” (Barthes 2010). The generic image is, in Galton’s idea, pure present, reference, model, idea. It represents what does not pass away in its eternal reproduction and what is able to absorb the singularity. However, as Galton’s own words show, these generic images remain haunted by ghosts, which, appearing as blurring, bring back the exorbitant, misleading, reticent, resistant, intractable, ephemeral, and elusive singularity.

2 The intractable face of the criminal

Galton invented composite photography as an expedient to analyze many photographs of criminals and to identify the physiognomic features of the face of the typical criminal. However, this first application of composite photography, unlike later ones, turns out, as Galton himself admits, to be a complete failure. Galton admits, reporting in 1879 on the results of his work on the photos of criminals, that the features of the generic face resulting from the overlapping of the photos of the criminals’ faces turned out to be much more “beautiful” than the singular.

It will be observed that the features of the composites are much better looking than those of the components. The special villainous irregularities in the latter have disappeared, and the common humanity that underlies them has prevailed. They represent, not the criminal, but the man who is liable to fall into crime. All composites are better looking than their components, because the averaged portrait of many persons is free from the irregularities that variously blemish the looks of each of them. (Galton 1879a: 135)

The criminal is the only case in which Galton admits a mismatch between the obtained and the expected results, as if, somehow, the criminal’s face had jammed that automatism of the transition from many to one that the composite photograph was supposed to guarantee. Galton’s reasoning is as straightforward as banal and is based on the correspondence of good/bad, beautiful/ugly, and regular/irregular pairs. The face that results from the composite of criminal’s faces is too beautiful and regular to be the face of an evil man, which should be ugly and irregular. While in all the other cases analyzed by Galton, the individual form seems to dissolve, to dilute within the general form that each singular represents only imperfectly, the face of the delinquent, on the other hand, seems to remain outside the generic face that results from the composite. Galton explains that the features that mark the criminal’s face result from his or her criminal history. They are, therefore, the result of events, are accidental, and, as such, cannot but disappear within the generic image, which shows a naked face without history or expression. In the naked, expressionless face of the generic image, the criminal does not show himself for what he has done, for what he has been, or for how he has lived, but in his essence, in what he “is” even before and regardless of the crime committed.

Galton’s terrible hypothesis is that composite image of criminal represents a “generic humanity” and, specifically, that part of humanity that has criminal tendencies, a humanity of the “low type,” Galton says in 1880 (1907: 11), which comes to coincide with the poor and working class. In this way, Galton interprets criminality as a hereditarily tendency that is common within the poorer strata of society. The generic image shows the criminal before the crime. The generic image, Galton says, shows the face of the criminal before the “mark of Cain” is imprinted on it (Galton 1879b: 162).

In this early application of composite photography, much more than in later applications, Galton marks the distance between the generic face and the face of the singular, even to the point of declaring the attempt to represent the generic face of the delinquent a failure. As Bataille points out, quoting Galton and his composite photographs in The deviation of nature (1985), what makes Galton’s project waver is “the monstrous.” “The brands of Cain,” “the feature brutalized by crime,” (Galton 1879: 162), and “the irregularities that variously blemish the looks of each of them” (Galton 1879a: 135) are all expressions Galton uses to connote an “unbearable,” “impossible to be handled” monstrosity:

In the large experience I have had of sorting photographs, literally by the thousand, while making experiments with composites, I have been struck by certain general impressions. The consumptive patients consisted of many hundred cases, including a considerable proportion of very ignoble specimens of humanity. Some were scrofulous and misshapen, or suffered from various loathsome forms of inherited disease; most were ill nourished. Nevertheless, in studying their portraits the pathetic interest prevailed, and I returned day after day to my tedious work of classification, with a liking for my materials. It was quite otherwise with the criminals. I did not adequately appreciate the degradation of their expressions for some time; at last the sense of it took firm hold of me, and I cannot now handle the portraits without overcoming by an effort the aversion they suggest. (Galton 1907: 12–13)

Galton admits, almost without explaining it, two different levels of dissimilarity, of which only one is “impossible to be handled.” The dissimilarity that is “impossible to be handled” relates to what Galton calls a “degradation of expression,” a dissimilarity, then, that concerns the face and, in particular, the expressivity of the face. Therefore, the face that is impossible to handle transcends the measurability of physical features: it is an immeasurable and unconquerable monstrosity, which only resembles itself and which, for this reason, composite photography fails to capture.

The reduction of the singular to the general, for Galton, has two possible and complementary modes: the first is the modality of the composite photograph, in which the singulars, compared by similarity, are composed into the general; the second is the modality of the “analytical photograph,” which by specific parameters measures the distance of each singular from the generic pattern obtained by composition. Both of these modes do not work when applied to the face of the criminal and its “special expression”: “The brands of Cain are varied; therefore, the special expressions of different criminals do not reinforce one another in the composite but disappear” (Galton 1879b: 162). According to Galton, the dissimilarity produced on the face by diseases can be measured, compared, and classified, but, in contrast, the dissimilarity of the criminal’s face, the dissimilarity of its expressions is so special and sui generis that it makes impossible any aggregation by similarity. For the particular expressions that mark the face that is criminal, there are no units of measurement, there are no possible classifications and, for this reason, the transition from the many to the one, in this case, is jammed.

Bataille says, referring to Galton in The deviation of nature: “Monsters thus would be the dialectical opposites of geometric regularity, in the same manner as individual forms, but in an irreducible way” (Bataille 1985: 55). The monstrous is the “individual form,” but in an irreducible way, it is the “sui generis” that does not return to the genus, since it cannot be included in any collection of resembling individuals. The opposition between general form and individual form tends toward a synthesis in which the singular finds its position in the general. By contrast, the opposition between the general form and the monstrous is a violent opposition in which the monstrous can only be excluded, obliterated, reclosed, erased, or eliminated.

Not only is Galton’s discourse on the face of the criminal extremely dangerous socially, politically, and legally, but it also poses an important theoretical difficulty, highlighting a sui generis (the face of the criminal) that is irreducible to the general.

Galton’s strange attitude to his first application of the composite image raises questions concerning the specific relationship between the singular and the universal that composite photography presupposes. While not entering into the merits of this complex philosophical question, Galton seems to take for granted the idea of a real universal immanent in matter. The use of the photographic medium and the idea of composite photography as “real generalization” seems to refer to an emanation of form from the singular, which in his view the photographic plate, even more than the human mind, is able to capture and objectively attest. Then, the no one’s face resulting from the composite photography is not a “technical construction,” but rather the technical unveiling of the reality of the “genus.”

The composite photograph, in Galton’s idea, was meant to be an “automatic” tool for reducing the singular to the general, but the monstrous expression of the criminal’s face jams this mechanism, raising the question concerning the relationship between the singular and the universal.

3 Jastrow: catching the living genre

In 1885, the journal Science published a series of articles devoted to the technique of composite photography, reporting on the realization of a composite image of the faces of the participants at the National Academy of Sciences convention in Washington in 1884. The expected result of this experiment was the generic image of the face of the “scientist.” Raphael Pumpelly’s article reporting on this experiment (Pumpelly 1885) is followed by an article of discussion by Joseph Jastrow (1885), who had taken Peirce’s courses at John Hopkins University in the early 1880s, and who co-authored with Peirce the essay On small differences of sensation (Peirce and Jastrow 1885), presented at the National Academy of Sciences in 1884. According to Signorini, who accurately reconstructs these events, the experiment at the National Academy of Sciences and its discussion by Jastrow is the occasion that brought Charles Peirce into contact with the technique of composite photography (Signorini 2009: 137), which, as we shall see in the next section, appears mentioned within some crucial junctures in the development of his semiotic theory.

Within the context of the National Academy of Sciences, the technique of composite photography loses its connection with Galton’s eugenic purpose and social Darwinism and is connected, instead, to the more philosophical-theoretical questions of the reality of universals. In the 1885 article in which he discusses the result of the National Academy of Sciences experiment, Jastrow clarifies that composite photography can serve two different purposes. The first purpose of composite photography is to obtain “a single type which shall represent the whole group.” The second purpose is to obtain a unified representation of the faces, which “shall give a superior effect by combining the strong points, and neglecting the defects, of each of the series” (Jastrow 1885: 165). The second purpose of composite photography is the one originally indicated by Galton, which is to produce the generic image. Composite photography, says Jastrow, echoing Galton, makes possible a mechanization of the processes leading to the “type” while avoiding those errors of judgment to which the human mind is instead subject.

Using composite photography in his second purpose, Jastrow writes, “however, we are introducing an essentially new face” (Jastrow 1885: 165). The use of “however” suggests that Jastrow, differently from Galton, perceives the introduction of this new face, this face of no one, as problematic. Jastrow, differently from Galton, looks for the ways through which it is possible that this “face of no one” that the generic image shows can represent “the face of someone,” thus reducing the distance between the singular and the general and moving away from the idea that the generic face is but an abstract construction. For this reason, Jastrow focuses on the first purpose of composite photography. In this first purpose, the generic image resembles a singular living face, thus perfecting that process of embodying the genre that in Galton remains, to some extent, incomplete. Indeed, the generic image for Galton not only has the features of a human face but, even better, is an existing human face. Writes Jastrow: “In several cases, when various images have been combined to elicit a type, it has happened that the resultant has been remarkably similar to one individual of the group represented” (Jastrow 1885: 165). In many cases, says Jastrow, the generic image corresponds to a singular face, which may be one of the faces overlapped into the composite or another face unrelated to the composite itself. In his description of the National Academy of Sciences experiment, Pumpelly points out that the resulting image appears extremely similar to a member of the Academy whose portrait was not used within the composite. Therefore, what Jastrow calls type (and Galton calls genre) could represent a singular and, conversely, one of the singulars could represents the type or genre.

Jastrow’s intent to reconnect the generic image with the existing singularity is not only shown in this search for an existing singular that represents the genre but also in the search for technical modalities to obtain the generic image from “actual life.” These are extremely complex technical modes, because working from “actual life” makes the delicate alignment of faces (on which the technique of composite photography is based) more difficult. Jastrow describes, within the article, his experiments with the stereoscope, which, with special arrangements and the use of mirrors, makes it possible to compose a pair of faces into a single visual image without imprinting them on the photographic plate, achieving a “lifelike effect” (Jastrow 1885: 166). Through the stereoscope, Jastrow seems to be looking for a generic “living” image, a generic face not fixed by the photograph, but actual, not only in the flesh, as even a corpse can be, but in act, alive. Jastrow seems, in this short article, to be pursuing the idea not only, like Galton, of making the genus appear, of making it visible, but, even more, of giving it life.

The idea of this generic “living” image that appears in Jastrow’s short articles on composite photography is not an extension but rather a total twisting of Galton’s idea. Galton’s generic image is formulated within the classical dichotomy between the sensible and the intelligible, or between the body and the idea, where, on the one hand, the sensible and the corporeal is variable, changeable, finite, and manifold and, on the other hand, the intelligible and the ideal is fixed, unchanging, infinite, and unitary. Jastrow’s need to get rid of the instantaneity of the photographic shot to look for a generic living image seems to presuppose a view of the general that is very different from Galton’s. In his search for the lifelike effect, Jastrow seems to presuppose the impossibility of definitively abstracting the general from the singular, the belonging of the general to the body, the connection of the idea with the face that embodies it.

4 From Jastrow to Peirce: giving body to the idea

In 1884, the same year he conducted research and experiments on composite photography, Jastrow presented, together with Peirce, the paper “On small differences of sensation” (1885) at the National Academy of Sciences. At this time, Peirce was working on the structures that mediate the analysis of the synthesis through which not only our representations but also our perceptions are constituted, increasingly disentangling himself from Kantian transcendentalism, which reduces these mechanisms to perceptual and mental biological structures independent of social and cultural factors.

The topic of “On small differences of sensation” seems at first glance disconnected from the issue of composite photography. This article, through an account of a series of experiments personally conducted by Jastrow and Peirce, focuses on the question of the relationship between the intensity of a stimulus and the intensity of the related perception. In this text Jastrow and Peirce show how the results of these experiments contradict, at least partially, Weber–Fechner’s law. Weber–Fechner’s law establishes a relationship of direct proportionality between the perceptual stimulus and the perceivable differential threshold, asserting that the larger the initial stimulus, the larger must be the difference between it and a subsequent stimulus in order for variation to be perceived. This means that if the change in the stimulus is minimal compared to the initial stimulus (e.g., the addition of a few grams to a hefty load), it does not necessarily produce a sensation of variation, and then what is perceived is a sameness and not a difference (Peirce and Joseph 1885: 77).

Although this issue may seem very distant from composite photography, it is remarkable that Galton, in his early articles on the elaboration of this technique, quotes Weber–Fechner’s law several times, demonstrating the imperfection of mental generic images compared to photographic generic images (Galton 1879: 167). In “Generic images” of 1879, Galton quotes Weber–Fechner’s law to support the idea that the human mind grasps exceptional and rare events better than usual and customary events. For this reason, according to Galton, the human mind produces a discrepancy between “the magnitude of the ‘subjective’ effect” and the “magnitude of the ‘objective’ cause” (Galton 1879: 167). Because of this discrepancy, perceptions that are very similar in intensity to the previous or the ongoing one, instead of confirming and reinforcing the former, as they do in composite photography, are not perceived, thus remaining outside the perceptual threshold.

Therefore, Galton uses the Weber–Fechner law to demonstrate the need for a technical expedient that mediates out the relationship with reality, eliminating the defects of our immediate relationship with reality that, instead, produces a subjective image of it, where this “subjective” is understood in the sense of altered, vitiated, and erroneous. The comparison implemented by Galton using the Weber–Fechner law is between the human mind and the photographic plate when used with the technique of composite photography. This comparison takes place on the ground of the possibility of making universals appear as reality, in the image of the generic face. In this confrontation, the body appears only as an object of perception, in the stylized image of the generic face embodying the universal, without being involved within the perceptual and representational process, except by its hindering, with its perceptual limitations and defects, the possibility of the intellectual intuition of universals. So, the Weber–Fechner law is used by Galton to support the idea that, in order to grasp the general, it is necessary for the body to step aside in order to eliminate its deficiencies, inaccuracies, and errors.

In “On small differences of sensation” Peirce and Jastrow focus on the body, which appears as a site of sedimentation of the synthetic processes that let us compare sensations individuating the differences. These synthetic processes in Peirce and Jastrow’s text, instead of being grounded in perceptual judgment, seem to retroact on it, conditioning it.

Peirce’s interest in Weber–Fechner’s law is undoubtedly motivated, in those years, by his work on the critique of intuition and on the processes that mediate our perceptual relationship with the world. Weber–Fechner’s law, in fact, by introducing a threshold of perception (in relation to prior perception or ongoing perception), works precisely on these processes of mediation, as it shifts the focus of the study of representation from the represented object to the modality in which the representing subject organizes the relations among perceptions. Intuition, as Peirce says at the end of the 1960s, is a sensation that is not preceded by other sensations (Peirce 1984: 193). The Weber–Fechner law confirms that each sensation is perceived in relation to the preceding sensation or to the ongoing sensation (I perceive the light of a candle being lit in a dark room, but I cannot perceive the same candle being lit in a room where many other candles are already lit).

The limitations Peirce and Jastrow identify in the formulation of Weber–Fechner’s law consist of the failure to distinguish between perception and perceptual judgment, which results from the reduction of the perceptual question on the ground of the consciousness. The results of Peirce and Jastrow’s experiments partially contradict Weber–Fechner’s law because they show that the threshold of sensation that this law identifies is valid, but only at the level of perceptual judgment, i.e. at the level of consciousness and representation. Jastrow and Peirce argue in “On small differences of sensation” that minimal perceptual differences are acquired and sedimented at the unconscious level, also leading, in the long run, to an improvement in the performance of the subject undergoing the experiment, such that as the subject is asked to evaluate small variations in weight, he or she becomes increasingly able to give the correct answer, even if he or she cannot rationally justify this answer and detect the difference at the level of perceptual judgment. This organic dimension of perception is not understood as a pure, immediate, and ante-predictive perceptual level but rather as a bodily level of synthesis, in which sensations are not perceived in isolation but related in a system of similarities and differences that precedes and conditions the judgment. This essay, remaining within an experimental-descriptive level, comes up with the idea that if the general is the product of synthesis, as the technique of composite photography seems to presuppose, the body becomes that which enacts these mechanism of synthesis and the place in which these mechanisms of synthesis are sedimented.

The question that Peirce and Jastrow raise in this text concerning Weber–Fechner’s law has in common with the question of composite photography the reflection on the mechanisms of synthesis that produce the transition from the singulars to the general. Moreover, in this essay Jastrow and Peirce conceive this mechanism of synthesis exactly as it is conceived by Galton’s elaboration of composite photography. Indeed they are conceived as processes of sedimentation by accumulation, rather than as ordering in a linear space-time dimension as occurs, for example, in Kantian forms of sensibility. Within Galton’s discourse, the support of these syntheses, the place of accumulation, overlapping, and sedimentation, is the photographic plate. In “On small differences of sensation,” the support becomes the body understood as a zone of non-control, as a preconscious ground in which not only synthesized data but also systems of organization of the real are sedimented.

At the time of the publication of “On small differences of sensation,” Peirce had already elaborated the concept of habit, defining it as a general rule of interpretation, as an organizational form of the manifold, i.e., as an operator of synthesis, as an active relation, as a way of holding things together, as syntax of the factual. Between the 1870s and the 1880s, thus in the context in which Peirce shifted from propositional logic to the logic of relations and in which he elaborated the structure of the three categories of Firstness, Secondness, and Thirdness that would constitute the constant set-up of his thought, Peirce focuses his reflection on these synthetic structures of perception, relating them, on the one hand, to the concept of community, thus to the social and cultural context of reference and, on the other hand, to the concept of organism, thus to the idea of the body.

In 1881, Peirce defined habits as “general rules to which the organism has become subjected” (Peirce 1989: 249; Peirce 1992: 226). These “general rules” are specific ways of arranging or organizing the facts. They are organizational habits of the manifold that, by activating relations, actualize the potential qualities of things. They are mechanisms of synthesis socially absorbed by bodies that are activated in perceptual processes. The activation of these synthetic mechanisms is not the expression of the free will of a self-sufficient and self-founded subject who chooses which organizational schemes to apply to things. The organizational schemas of the real are habits to which an organism has become subjected. The organism, the body, in this sense, is not defined as a biological fact but as the cultural-historical sedimentation of organizational schemas that activate mechanisms of synthesis on the perceived. These organizational habits, these relational forms, are not what are preventing me from accessing the thing itself. On the contrary, they are perceptual schemas of the world that embody the subject and give it back the body necessary to perceive the world, not a biological body but a social and cultural body whose way of seeing the world cannot be independent of the position from which one views it, from the relationships in which one is embedded, and from the languages in which the world is told to us. This idea of the body is very different from the Galtonian biological body, on whose surface appear the hereditary characters that mark its distance from the generic image.

Peirce, between the 1890s and the early twentieth century, uses composite photography as a metaphor for these bodily mechanisms of perceptual synthesis that mediate our relationship with the world. Specifically, in the early twentieth century, composite photography is used as a metaphor in the analysis of the “percept” in the context of the phaneroscopy. The “percept” says Peirce in 1903 is pure presentation. It “imposes itself on my gaze, but not as a substitute for something else; it, simply, knocks at the doors of my soul and remains on the threshold,” insisting in silence and imposing its own inevitable appearance (Peirce 1966: 369–370). What places the percept on the threshold of representation is precisely this “remaining,” this “insisting.” Peirce says: “It is a forceful thing. Yet it offers no reason, no excuse for its presence. It silently forces itself upon us” (Peirce 1966: 370). This “insistence” and “permanence” is a kind of embryonic generalization, which causes the qualities of sensations to be, in some way, associated and related to each other, within a process of synthesis that precedes perceptual judgment. In 1901 Peirce described the synthetic nature of percept as a “coalescence” (Peirce 1966: 111), a synthesis by accumulation. There is “something” on my table, Peirce says to explain this process, and this “something” comes out of impermanence by standing out from everything else. This “something” lingers before the eyes so much so that it is possible to observe it from different perspectives. In this attempt to show this synthesis that precedes judgment, this bodily, organic synthesis, Peirce often uses the image of the composite photograph as a metaphor. Each of the percepts that are realized in the perception joins by coalescence with all the others, a moment before I, through inference, can say that what I see is an inkwell: “What I call an inkwell is a generalized percept, a quasi-inference from percepts, perhaps I could say a composite photograph of percepts” (Peirce 1966: 111). In this sense, the image of the composite photograph serves to figure a process within which the general is formed by overlapping by accumulation (as the Galtonian generic image) rather than by abstraction. Through the image of this composite photograph, Peirce shows that the general quality (the Galtonian generic image) does not detach itself from the singular, from the sui generis but holds it within itself as its material of construction.

In this specific use of “composite photography,” Peirce deeply modifies Galton’s idea. Galton starts from the singular in order to obtain a general, acting within the classical idea of a subject of knowledge that starts from itself, that starts from its own experience of the world in order to obtain, through technical expedients, that objectivity that for him was constituted by the generic image. Peirce, on the other hand, uses the composite photograph as the image of the percept to explain how the “general” is not the result of our perceptual judgments but, instead, on the contrary, the schema through which we organize the perceived: this “general” is not, therefore, the result but, rather, the presupposition of perceptual judgment. In using the metaphor of the composite photograph, Peirce is reasoning in a totally different way than Galton. It is not a matter of constructing the composite photograph in order to finally understand the essence of the singular. Rather, it is a matter of reflecting on the representational, hence semiotic, schemas that filter my access to the world.

What fundamentally changes in Peirce’s use of composite photography is the conception the body. For Galton, the body is that which must be brought back to the general, which must conform to it. For Peirce, on the other hand, the body becomes the place of sedimentation of rules of synthesis within which the singular, the sui generis, is taken in relational schemas, which are not the expression of the free will of a self-sufficient and self-founded subject but “habits to which an organism is subjected.” The body, in this sense, is no longer, as in Galton, a mere biological fact determined by biological-hereditary factors but the cultural-historical sedimentation of organizational rules. In this context, the “general” is no longer understood, as in Galton, as a “model” in the sense of the Platonic “idea” of which the singular is a copy. The general, the idea, becomes a specific mode of synthesis that mediates our perception of the word, activating those coalescence mechanisms on which perceptual judgment is layered. In this sense, the general, or the idea, is a form of relation, a potential aggregate, says Peirce in the 1880s (Peirce 1965: 132), where what remains constant is the “how” of the relation while it changes, instead, what is related.

This “how” is what Peirce says in the early twentieth century, “gives body” to the idea (Peirce 1960: 283–284), or, rather, makes the idea, the general, a body, an organism, embodying it within specific ways of activating processes of synthesis in its perceptual relations with the world.