Introduction
According to Joseph Campbell, myths are profound metaphors and symbolic maps of the human psyche that reflect universal experiences like love, adversity, and transformation. In A Hero with a Thousand Faces, he draws on archetypal imagery, including the hero, the guide, the shadow, and, especially, the mother. In his account, the mother becomes a symbolic origin point, often detached from the specificity of any individual woman, to tell stories and create living myths that transform ordinary moments into meaningful visual narratives.
Roland Barthes recognizes similar mythic structures across oral and linguistic histories but offers a fundamentally different account of how myth functions in photography. He contends that a text’s meaning belongs to the reader, not the creator. When this logic is applied to the realm of photography, Barthes insists that while the viewer is the meaning maker, photography’s power lies in its ability to make the viewer feel as though they are not producing meaning at all but simply encountering a self-evident truth. Photography becomes a perfect vessel for Barthes’s argument about mythical speech: the medium captures historical, physical acts and transforms them into naturalized, eternal “truths.”
In this paper, I trace two dominant visual regimes: the sentimental and the clinical, through which photography constructs birth as a universal human experience while simultaneously erasing the mother as a historical subject. Both types of looking transform historically situated bodies into signs of universal truth. The sentimental image (Steichen) produces identification through emotion and familial intimacy, while the clinical image (Nilsson) produces awe through scientific authority and technological mediation. Despite their different aesthetics, both detach the subject from history: one through feeling, the other through abstraction. This detachment naturalizes birth as an eternal, apolitical condition as opposed to a socially structured and embodied experience.
Steichen and Nilsson use the camera to present what appears to be a universal truth of life, yet they ultimately erase the individual woman. Carmen Winant’s collage of birthing photographs attempts to overwhelm this erasure through the sheer volume of maternal labor. Roland Barthes’s “Winter Garden Photograph” presents the ultimate resistance: by remaining unseen, his mother’s body remains her own, escaping the clinical and sentimental myths that seek to universally humanize her. Modern photographic representations of birth produce a humanist myth through both sentimental and clinical visual regimes, each of which erases the mother as a historical subject. Through the work of Winant and Barthes, alternative visual logics of excess and absence emerge that resist and expose this myth.
Sentimental Vision and the Myth of Universal Humanity
Figure 1: Wayne Miller, Childbirth, 1950s, gelatin silver print, in The Family of Man, curated by Edward Steichen (New York: Museum of Modern Art, 1955).
Wayne Miller’s portrait of a baby’s delivery, included in Edward Steichen’s The Family of Man exhibition (1955), depicts birth as a moment of deep intimacy and universal human experience. The black and white photograph depicts a woman in labor, her body covered in blankets yet vulnerable to the camera’s gaze, and a masked physician, who is her husband, facilitating the birth. Sentimental myth is constructed by a meticulous orchestration of textures and light that anchors the universal in the highly particular. The physician’s mask, an intense white rectangle against a dark background, symbolizes professional authority, yet its soft fabric texture implies a tenderness that contrasts with the clinical coldness of later medical imaging. The physician’s hands, partially concealed yet engaged, maneuver amid the creases of thick, crumpled white sheets. These sheets are not the sterile, throwaway plastics found in contemporary hospitals; they possess a domestic, tactile quality, indicating a connection between the clinical environment and the home.
The light in the shot is directed and striking, akin to Caravaggio’s chiaroscuro, generating strong shadows that obscure the “mess” of the delivery while emphasizing the emotional bond between the doctor and child. The physician, identified as the woman’s husband, is situated not just as a medical practitioner but also as a witness. Miller captures the reflection of light on the doctor’s eyeglasses and the gentle blur of the baby’s developing head, crafting a moment in which the viewer is not a voyeur but an active participant in a sacred ceremony. Each detail, such as the fabric’s creases, the mask’s straps, and the shadows of the two gloved hands assisting in this moment, persuades the observer that they are experiencing the “Self-Evident Truth” of human creation. The “thickness” of these features enables the image to surpass its 1950s setting and function as a timeless, mythological symbol of the “Family of Man.”
Miller’s photo serves a fundamental purpose within the The Family of Man (1955) exhibition. By positioning birth at the beginning of the showcase, Steichen delineates what he refers to as a “circle of life,” implying that all humans, irrespective of nationality, class, or historical context, are interconnected by identical biological origins. This curatorial approach converts a distinctly embodied phenomenon into a symbolic depiction of human uniformity. Roland Barthes argues in his critique of the exhibition that such representations function through myth; they remove events of their historical and social character to depict them as natural, everlasting truths (Barthes 1972, 100–102). The body of the woman in labor is effectively absent and transcends specific social or medical contexts. She emerges as a symbol of universal humanity.
The photograph’s emotional impact is important to this process. The picture fosters a profound sense of identification through its focus on closeness, compassion, and shared experience. Viewers are encouraged to identify themselves within the scenario, perceiving birth as a timeless and globally shared experience. The photograph’s sentimental character arises from its ability to convert the particularity of delivery into an emotional feeling of communal connection.
However, this emotive universalism comes with a price. Allan Sekula contends that humanist photography frequently universalizes experience, concealing the social and economic frameworks that distinguish people (Sekula 1981, 15). The Family of Man (1955) exhibition prioritizes a collective human experience, obscuring the disparities and material circumstances that shape reproductive experiences, such as access to healthcare, gendered labor relations, and institutional regulations governing birthing. The husband’s dual role as partner and physician exemplifies a particular mid-twentieth-century arrangement of medical authority and domesticity.
Through this sentimental framing, the photograph participates in the production of what Barthes identifies as myth, an ideological structure that naturalizes historically contingent realities, making them appear timeless and inevitable (Barthes 1972, 142). In this sense, the photograph performs a dual operation. On the one hand, it foregrounds the physical and emotional intensity of childbirth, rendering it visible in a way that was considered radical for its time. On the other hand, it abstracts this experience from its social and historical conditions, transforming it into a myth of human sameness. The laboring woman’s body, though central to the image, is ultimately depersonalized: the photo is a symbolic vehicle for a broader narrative of universal life, not a scene of individual experience.
Clinical Vision and the Myth of Scientific Life
Figure 2: Lennart Nilsson, “Drama of Life Before Birth,” Life Magazine, April 30, 1965.
Lennart Nilsson’s “Drama of Life Before Birth,” released in LIFE Magazine in 1965, presents one of the most significant graphic representations of human pregnancy in the twentieth century. The classic depiction of the fetus, hovering in a black, boundless abyss, is frequently regarded as a success of scientific imaging. However, its artistic composition challenges this assertion of impartiality. Instead of presenting a purely clinical aesthetic, the image employs a decidedly sublime visual language: the fetus emits an ethereal light on a dark backdrop, separate from any discernible maternal form. This compositional decision reinterprets the womb as an abstract, cosmic realm, situating the embryo as an independent, nearly mythological entity.
This visual separation is fundamental to the image’s ideological function. The black vacuum operates as a means of erasure from the mother’s body. Through the elimination of evidence of the maternal body, the image disassociates the fetus from the physical, social, and historical contexts of conception. This process generates what Roland Barthes refers to as “mythical speech,” in which historically specific facts are converted into naturalized, self-evident truths (Barthes 1972, 142). Birth is perceived not as physical work but as an abstract phenomenon.
Significantly, Nilsson’s own narrative of his methodology illustrates the degree to which this “miracle” is technologically and artistically fabricated. In a 2001 PBS interview, Nilsson clarifies the application of endoscopic techniques, specialized illumination, and invasive methods to obtain fetal pictures, emphasizing that these images need much experimentation and technical expertise (Nilsson 2001). This description clarifies that the photos are not authentic representations of life developing spontaneously in utero but are meticulously orchestrated as visual constructs. The fetus seems independent because the representation has been crafted to create that illusion.
According to Lisa Cartwright, medical imaging technologies do not only document the body; they actively recreate it, generating visual authority that detaches patients from their actual experiences (Cartwright 1995, 3). Nilsson’s images illustrate this phenomenon: its credibility relies on the illusion that the observer is observing an unaltered biological truth when the image is, in fact, a product of mediation, intervention, and artistic composition.
Rosalind Petchesky has extensively considered the ideological consequences of this visual logic, asserting that fetal imaging portrays the fetus as a distinct entity, apart from the maternal body that nurtures it (Petchesky 1987, 266). In Nilsson’s photographs, this division is very explicit. The fetus’s growth is depicted as self-driving, but the maternal body remains obscured and diminished to an unseen foundation that cannot be represented within the context. As such imaging was more broadly adopted by practitioners, the results of these new modes
of visualizing the human body came to be considered documents of objective truth.
Nilsson’s images not only reframe visibility but reorganize medical knowledge itself. By prioritizing the visual, the skills of touching and hearing within the medical field are lost. The clinical gaze was once diagnostic through the smell of breath, the texture of skin, or the rhythm of a pulse. These are sensory data points that require physical proximity, something that Nilsson’s machines eliminate for the practitioners and viewers. Endoscopes and other medical imaging technologies create scenarios where physicians often find themselves treating the patient, in this case the mother, as a digital record and not a living person. When a doctor and a patient look at scans together, they are both looking away from each other and at the screen.
The patient is most vulnerable when they are “unseen” as a person and only seen as a “pathology.” The machine abstracts the woman into a set of coordinates, making it easier for the professional to maintain a psychological distance, culminating in a crisis of empathy between the patient and the doctor. The mother knows her pregnancy through internal sensation, weight, and movement, while the physician “knows” the pregnancy through the digitally rendered image. When the image becomes the primary site of “truth,” the mother’s sensory testimony: her pain, her exhaustion, or her intuition, is relegated to the status of “subjective data,” which is always deemed less reliable than the “objective” visual output of the machine. The machine becomes the overwhelming authority.
The pervasiveness of these images changes a woman’s internal geography. Now, a woman can imagine herself as transparent. Before Lennart Nilsson, the womb was a “black box,” a site of mystery and folk knowledge. Now, women can envision their insides as a high definition, lit-up space. This erases the “sacred” or “private” essence of the interior and displays it for all to witness on the cover of LIFE Magazine.
The image’s emotional impact derives from its ability to create both distance and closeness. Although its soft glow and intricate details inspire admiration, this admiration is essentially disembodied. According to Barthes in Camera Lucida, the image exhibits a certain “weightlessness,” separating its subject from the gravity of actual experience (Barthes 1981, 92). Nilsson’s fetus illustrates this condition: it is physically weightless, suspended beyond the confines of time, space, and human struggle. The outcome is a contradictory representation that is simultaneously clinical and sentimental. It is scientific in its technological foundations, yet profoundly mythological in its aesthetic and ideological implications. This fusion renders the photograph a portrayal of life that hides the tangible realities of pregnancy and labor, substituting them with a generalized depiction of miraculous origins.
Material Multiplicity and the Refusal of Myth
Figure 3: Carmen Winant, My Birth, 2018, mixed-media installation, Museum of Modern Art, New York.
Carmen Winant’s My Birth (2018) presents an intriguing contrast to the sentimental and clinical visual perspectives common to photographic depictions of childbirth. Initially seen at the Museum of Modern Art, the piece comprises over 2,000 rediscovered photographs of women in labor and childbirth. The images, derived from an extensive collection of books, magazines, and personal archives over several decades, including feminist works like Our Bodies, Ourselves, are curated into a substantial, immersive installation that floods the observer with its vastness and variety. In contrast to the solitary, meticulously crafted pictures of Steichen and Nilsson, My Birth (2018) eschews coherence, hierarchy, and visual restriction.
While Steichen’s The Family of Man (1955) transforms childbirth into a universal emblem of human solidarity, Winant reinstates the uniqueness and materiality that such readings become obscure. According to Barthes, myth functions by removing events from their historical and social contexts to depict them as natural and eternal (Barthes 1972, 142). Winant’s initiative explicitly opposes this rationale. By showcasing thousands of pictures of laboring bodies, each differentiated by variations in race, environment, posture, and emotion, she emphasizes delivery as a historically contextualized and physically difficult process. The recurrence of related yet diverse visual elements prevents the viewer from consolidating these pictures into a singular, universal narrative.
The installation’s dense arrangement eliminates any space for abstraction or idealization, directly confronting the audience with the unyielding materiality of work. Blood, strain, fatigue, and closeness permeate the photographs, defying any effort to aestheticize or sentimentalize the event. In this context, Winant substitutes the myth of birth as a miraculous genesis with a focus on birth as labor: a repetitive, physical, and variably experienced process.
This method is clarified by Georges Didi-Huberman’s theoretical framework, which posits that a collection and juxtaposition of pictures may disrupt solitary narratives and create a fragmented, historically informed style of perception (Didi-Huberman 2018, 45–47). Winant creates a visual landscape where meaning arises via comparison, repetition, and contrast. The observer is not directed toward a singular interpretation but compelled to think through a multifaceted archive of lived experiences.
Unlike the solitary “heroic” portrayal of childbirth depicted in Steichen’s exhibition, My Birth (2018) rejects the simplification of labor to a mere symbolic event. Numerous pictures render it very hard to identify a definitive depiction. This work emphasizes the irreducibility of each unique experience. Through this accumulation, Winant generates a history, not a myth. Her curation emphasizes the material conditions, physical labor, and social situations influencing delivery. By doing so, she presents an alternative method of representation rooted in collaged multiplicity and embodied actuality.
The juxtaposition of Wayne Miller’s solitary representation in The Family of Man (1955) exhibition and Carmen Winant’s multiplicity in My Birth (2018) illustrates two conflicting visual paradigms: one that distills childbirth into a universal symbol, and another that emphasizes its inherent diversity. If these techniques depend on visibility through singularity or abundance, Roland Barthes presents a fundamentally distinct model: the preservation of the mother figure through absence.
The Private Gaze of Absence and the Limits of Representation
Figure 4: Odette England, Keeper of the Hearth, 2020. A collection for the “Winter Garden Photograph” and the preservation of the maternal punctum.
While Steichen and Nilsson eliminate the maternal figure through visible strategies, either by integrating her into a universal story or by abstracting her into technical absence, Roland Barthes proposes a fundamentally distinct method: the conservation of the maternal figure through invisibility. In Camera Lucida, Barthes presents the “Winter Garden Photograph,” an image of his mother as a child, which he elaborates on but eventually declines to print for publication (Barthes 1981, 67–70). This omission is not accidental but fundamental to his thesis. By withholding the photos, Barthes prevents the conversion of his mother into a generic or commodified image.
Barthes’s decision to withhold the Winter Garden photograph in Camera Lucida is a profound act of reclamation for his mother. Nilsson’s clinical perspective aims to make the maternal interior “transparent,” but Barthes acknowledges that complete visibility constitutes a type of violence. He writes, “I could not examine my mother’s features… I could not ‘explore’ her’” (Barthes 1981, 69). This rejection of “exploration” directly contradicts Nilsson’s endoscopic “voyage.” According to Barthes, seeing the mother’s body through a lens results in the loss of her identity as an individual.
In the Winter Garden vision, he discovers what he refers to as the “air” of his mother: a distinct, irreplaceable essence of her existence that “is the luminous shadow which accompanies the body” (Barthes 1981, 110). By maintaining this “air” of privacy, he shields her from the “stadium” of the public, where she would surely be transformed into a symbol of “Womanhood” or “Grief.” In this regard, the Winter Garden Photograph is the only image in this analysis that permits the mother to be perceived as a historical person rather than a mythical entity. Her preservation is not attributed to her role as “The Mother,” but to her identity as his mother, a distinction overlooked by both Steichen’s universalism and Nilsson’s scientific approach.
Barthes articulates this rejection through his differentiation between studium and punctum. The studium denotes the cultural and linguistic connotations of an image, those that are shareable, interpretable, and generally understood, whereas the punctum signifies the profoundly intimate and emotive detail that “pierces” the observer (Barthes 1981, 26–27). According to Barthes, the Winter Garden Photograph holds value precisely because it transcends the communicative domain of the studium; its importance resides in a personal, irreducible connection that cannot be conveyed to others. He asserts that an image imbued with significant emotional resonance for one observer may be completely devoid of impact for another (Barthes 1981, 73). The picture defies the universalization processes that underpin both sentimental and scientific depictions of birth.
In Camera Lucida, Barthes’s quest for his mother’s image transcends the pursuit of a “figure” or a “heroine”; it is an exploration of the soul. By declining to publish the Winter Garden Photograph, Barthes enacts a profound intervention against the “hysteria” of History. According to Barthes, History constitutes a public, chaotic spectacle; it incorporates Steichen’s “Family of Man” and Nilsson’s “Scientific Breakthrough.” History attempts to categorize, to label, and to transform the person into a representative of a category. In stating, “I could not transform her into a Heroine, a Figure; I experienced her as a unique being,” Barthes is explicitly deconstructing Joseph Campbell’s monomyth (Barthes 1981, 71). Joseph Campbell perceives the Mother as an archetypal “threshold figure” that aids the hero’s journey (which is imagined in the context of a man), but Barthes regards his mother as an individual in her own right, resistant to any symbolic role.
The division between the “General Mother” and the “Particular Mother” constitutes the critical boundary upon which photographic ethics is founded. The “General Mother” is a conceptualization of the studium; she represents the woman in childbirth in Miller’s image or the transparent vessel in Nilsson’s endoscope image, denoting “Nature.” These outcomes are “hysterical” in the Barthesian context, as they exist solely for observation, classification, and the reinforcement of a universal narrative. They are classified as “History” due to their inclusion in a collective, public lexicon. Conversely, the “Particular Mother,” understood in the descriptive language of the unreleased Winter Garden image, is within “Time.” History is static and ideological, but Barthesian time is dynamic, internal, and regulated by the punctum.
In this analysis, the “Winter Garden Photograph” becomes a significant blind spot of seeing: a fourth image characterized by its absence rather than its presence. While the preceding photos encourage interpretation, circulation, and comparison, Barthes’s archival photo rejects all three. It is not subject to visual analysis, cannot be integrated into a larger story, and cannot be distilled into a symbol. This rejection serves as a criticism of the other visual frameworks discussed here: it reveals how visibility may facilitate erasure, converting persons into symbols that fulfill ideological purposes.
Contemporary artistic practices have taken up this absence as a productive site of inquiry. Odette England’s Keeper of the Hearth (2020) presents a particularly poignant reaction to Barthes’s absent image. In this project, England requested more than 200 photographers and artists to contribute an image serving as their own “Winter Garden Photograph,” a personal depiction of their mother or a maternal figure of intimate importance. The resulting collection converts Barthes’s unique, personal image into a communal, yet inherently multiple, array of representations. Like Carmen Winant’s My Birth (2018), England’s project utilizes multiplicity as a formal method; but, instead of inundating the audience with the abundance of birthing, it curates a constellation of personal pictures that defy synthesis into a cohesive narrative.
This surge of pictures further undermines the concept of a universal maternal archetype. Steichen’s idea relies on a universally acknowledged “human” experience, but England’s archive illustrates that such universality is unattainable. Every picture is rooted in a distinct, intimate relationship, reflecting Barthes’s assertion that individual emotion is irreducible. The maternal figure, in this setting, cannot be compressed into a symbol without forfeiting the essential elements that provide its significance.
This focus on the constraints of sight aligns with Tina Campt’s assertion that pictures can function through subtle, emotional dimensions that lie beyond what is readily seen or comprehensible. In Listening to Images, Campt suggests that visual practices often communicate through subtle, non-spectacular forms of resistance that require modes of engagement beyond looking (Campt 2017, 6–8). Barthes’s decision to withhold the Winter Garden Photograph might be seen as a rejection of the requirements of visual consumption. The picture communicates not by its presence but with its absence, eliciting a distinct form of attention rooted in emotion, memory, and relational dynamics.
Barthes and England collectively suggest a distinct visual logic that does not generalize or inundate the viewer but highlights the constraints of representation itself. While Steichen creates myth through singularity and Winant undermines it through multiplicity, Barthes finally transcends it through absence. In this manner, he maintains the mother figure as a connection that escapes total portrayal, sharing, or translation into a visual form.
Recontextualizing Visibility in Photography
Romantic and clinical representations of birth serve to obscure the mother through mythmaking; nevertheless, it is essential to refine this assertion by examining how these visual frameworks also facilitated new forms of visibility. Characterizing these photographs only as instruments of erasure neglects their historical importance in rendering childbirth publicly visible, especially within the visual culture of the mid-twentieth century.
Edward Steichen’s The Family of Man (1955) arose in a postwar period characterized by a yearning for global cohesion and human interconnectedness (Stimson 2006, 11). The use of birthing images in this show was, in several respects, revolutionary. It introduced a personal, frequently secluded experience into the public domain, positioning it as fundamental to the human experience. Lennart Nilsson’s fetus photos, extensively distributed by LIFE Magazine, broadened public exposure to previously deemed inaccessible aspects of pregnancy. His photos provided viewers with an intimate understanding of biological processes that have historically been concealed, unattainable, and abstract.
From this viewpoint, Steichen and Nilsson might be perceived as engaging in a more extensive visual endeavor of public disclosure. They do not only cover or eliminate the maternal body; instead, they recontextualize its visibility within emerging frameworks of photographic and scientific authority. The issue lies not in visibility per se, but in the conditions that govern its structure and interpretation.
This conflict exposes a fundamental paradox: these pictures render birth increasingly apparent while also restructuring that visibility through myth. In Steichen’s work, the working body is made apparent only to the extent that it can be integrated into a story of universal human interconnectedness. In Nilsson’s photographs, the fetus is rendered hyper-visible solely by the methodical obliteration of the maternal body that nurtures it. In both cases, visibility is contingent. It is conferred through procedures that separate the subject from its historical and corporeal particularity.
It is more beneficial to see these early birth photos as functioning within a paradoxical visual economy. They simultaneously disclose and conceal. They generate information while also constraining the parameters through which that knowledge may be comprehended. The concern lies not just in the mother’s disappearance but in the transformation of her presence into an overarching ideological narrative of universality, scientific advancement, and humanist mythology. This recontextualization fosters a transcendence of the dichotomy that exists between visibility and erasure, prompting an examination of the circumstances that render certain bodies visible.
Conclusion
In The Hero with a Thousand Faces, Campbell delineates the mother as a recurring archetype within the “monomyth”: she embodies origin, nurturer, and threshold figure, representing both the inception of life and the conditions of human development (Campbell 2008, 23–30). In many mythological traditions Campbell analyzes, such as the figure of the Great Mother or Earth Mother, the maternal body is a cosmic origin, an entity that gives life while remaining outside of history (Campbell 2008, 13–15).
Contemporary photography executes a comparable function under the disguise of realism. The sentimental gaze (Steichen) portrays the mother as the emotional foundation of universal human connection; the clinical gaze (Nilsson) reduces her to a biological context that generates life; Winant’s multiplicity counters this simplification by reinstating birth within the domains of labor and plurality; and Barthes’s absent image entirely rejects the myth, maintaining the mother as uniquely singular. Collectively, these four perspectives demonstrate that what is seen as “universal humanism” is a constructed myth that becomes reliant on the conversion of a mother’s body into an archetype.
Photography surpasses its role in documenting birth; it mirrors a modern interpretation of Campbell’s mythical framework, positioning the mother as a symbolic origin story, not a historical figure. Modern visual culture continues to rely on myth while disavowing it. As Barthes and Winant would attest, this myth is not fixed. By replacing the miracle of the archetype with the excess of the labor of childbearing and the ethics of maternal absence, these alternative visual logics reveal the price of universal humanism. The essential truth of the maternal body lies in the intangible, intimate narrative that the camera can never fully capture.
Works Cited
Barthes, Roland. 1972. Mythologies. Trans. Annette Lavers. New York: Hill and Wang.
Barthes, Roland. 1981. Camera Lucida. New York: Hill and Wang.
Cartwright, Lisa. 1995. Screening the Body. Minneapolis: University of Minnesota Press.
Petchesky, Rosalind Pollack. 1987. “Fetal Images…” Feminist Studies 13 (2): 263–92.
Nilsson, Lennart. 2001. “Behind the Lens: An Interview with Lennart Nilsson.” PBS NOVA.
Didi-Huberman, Georges. 2018. Atlas, or the Anxious Gay Science. Chicago: University of Chicago Press.
Sekula, Allan. 1981. “The Traffic in Photographs.” Art Journal 41 (1): 15–25.
Campt, Tina. 2017. Listening to Images. Durham: Duke University Press.
Joseph Campbell, The Hero with a Thousand Faces (Princeton, NJ: Princeton University Press, 2008).
Wayne Miller, Childbirth, ca. 1950s, gelatin silver print, in The Family of Man, curated by Edward Steichen (New York: Museum of Modern Art, 1955).
Winant, Carmen. My Birth. 2018. Mixed-media installation. Museum of Modern Art, New York.
England, Odette. Keeper of the Hearth. 2020. Artist’s book project.
Lennart Nilsson, “Drama of Life Before Birth,” Life Magazine, April 30, 1965.
Stimson, Blake. The Pivot of the World: Photography and Its Nation. Cambridge, MA: MIT Press, 2006.