What causes homosexuality? Opium indulgence, warm climate, and working in the profession of decorator are just three examples selected from a dizzying number of causes suggested by the German sexologist Iwan Bloch. The etiology of sexuality, in particular homosexuality, preoccupied sexologists in the late nineteenth and early twentieth centuries. Focusing predominantly on a US context and with reference to scientific and literary sources spanning a period from the 1850s to the 1930s, The Book of Minor Perverts: Sexology, Etiology, and the Emergences of Sexuality traces how multiple sexualities were largely forgotten or obscured in order to be replaced by one: homosexuality.
The debate around sexual etiology in the late nineteenth century was split into two major models of homosexuality as either acquired or congenital. But, Kahan argues, the sheer variety of causes enumerated by sexologists suggests “the radical instability, unevenness, and messiness of the emergence of sexuality” (2). Tracing a number of etiological explanations for sexuality across five chapters, Kahan develops a critical approach to the emergence of sexuality which he calls historical etiology: “my approach is etiological in the figural sense, providing an account of the concept of homosexuality by examining the forgotten intellectual systems and etiological assumptions from which it emerged” (2). Kahan does so by uncovering other—in the words of Foucault—“minor perversions” which cannot be understood within a hetero/homo binary or as homosexuality, and which, having been gradually replaced by homosexuality, we have since almost forgotten. In opening up and diversifying the emergence of sexuality into various and conflicting narratives, The Book of Minor Perverts also follows Stephanie Foote’s lead to investigate “vernacular sexology”: whereas scholarship on sexology has often focused on sexology as medico-scientific discourse or on the clinical encounter between doctor and patient, more recent scholarship on the inter-disciplinary history of sexology has shown that in Britain and the German-speaking world, sexological research was never a solely scientific discipline, but always drew on neighbouring discourses and media, including anthropology, literature, and film. Kahan contributes to this trend in the study of historical sexology by analysing how scientific and literary texts co-construct and debate competing etiologies of homosexuality.
The Book of Minor Perverts is critically oriented around a lacuna in the work of literary scholar and queer theorist Eve Kosofsky Sedgwick. In Epistemology of the Closet (1990), Sedgwick argues that the invention of sexuality is the moment at which the hetero/homo binary congeals, as object choice becomes the determining attribute of sexuality. Sedgwick calls this “the Great Paradigm Shift.” Although Sedgwick claims the importance of the Great Paradigm Shift, she offers no explanation for its emergence. Kahan promises to think with and beyond Sedgwick by investigating how the Great Paradigm Shift came about. In doing so, he also re-examines established narratives of sexual modernity, where sexuality is lodged tightly within modern subjectivity:
in its methodological focus on fully formed subjects, sexuality studies as a field has not adequately examined the discourses that forged sexual personhood […]. This has meant both the exclusion of racialized subjects as not fully human, as not people, but also the exclusion of acquired sexual practices and minor perversions that have not crystallized into varieties of personhood or come to be understood as congenital and biologized. (7ff)
The Book of Minor Perverts offers an answer to this pressing need to investigate non-subjective forms of sexuality prior and subsequent to the Great Paradigm Shift by examining the messiness of sexuality in the late nineteenth and early twentieth centuries: as the hetero/homo binary congeals, what other “minor perversions” remain in the air and are gradually but, as Kahan shows, not fully, replaced by the homo/hetero binary? In doing so he challenges established scholarship in the history of sexuality, for example the view put forward by historians including Robert Beachy, Jennifer Terry, and John D’Emilio, that a model of homosexuality as congenital was representative of sexological thought during the late nineteenth and early twentieth centuries. Kahan argues that this is not the case, and that models of sexuality as acquired were important during this period and were the subject of serious sexological consideration (14ff).
In each of his five chapters, Kahan outlines one historical etiology of homosexuality, from environmental and temporal to volitional, in order to show the co-existence of multiple models of sexuality which slowly—but not entirely—congeal into a hetero/homo binary. As these etiologies contribute several new frameworks for thinking about the emergence of homosexuality as sexual subjectivity with a stable object choice, I want to describe these in some detail.
Chapter 1, “The Walk-In Closet: Situational Homosexuality and the Always of Desire,” explores how the tension between congenital and acquired models of homosexuality found expression in the preoccupation with sexual rhythm, where periodicity is pitted against the constancy of desire. With reference to two plays about female homosexuality—Thomas Dickinson’s Winter Bound: A Play in Three Acts and Nine Scenes (1929) and Lillian Hellman’s The Children’s Hour (1934)—Kahan outlines how a temporal and geographical model of homosexuality as situational resists a subjective model of sexuality as continuous psychology. As heterosexuality was increasingly defined through the stability of desire and object choice, the situational acquisition of homosexuality due to boredom or starvation was considered a minor perversion. Although “sexual identity’s temporal ‘always’” (26) gradually takes hold of homosexuality, too, Kahan’s analysis of situational homosexuality in this chapter reclaims periodicity, for example the cyclical periodicity of the seasons as expressed in Winter Bound, as “a crucial site of same-sex erotics” (33), ultimately revealing that temporality and migration “foreground the temporal and geographical situatedness of all sexualities” (22).
Chapter 2, “Anthropologia Sexualis, Universalism, and the Macro Environments of Sex,” narrates a shift from understanding the body as open to environmental influences to one that understands bodies as impermeable and fixed. In this process, the body becomes the stable vessel for sexuality and congenital models of sexuality can take hold. Kahan argues that, at the turn of the twentieth century, the seasons (as discussed in Chapter 1), weather, temperature, air, food, exercise, sleep, excretion, and venery were all understood to influence the body and its sexuality. Kahan follows sexologist Iwan Bloch in describing this as an anthropologia sexualis: unlike a scientia sexualis, which seeks to individualise, categorise, and discipline, anthropologia sexualis universalises and seeks to understand sexuality’s environmental influences. This second chapter outlines this environmental understanding of sexuality with reference to the work of several well-known sexologists, including Bloch, Havelock Ellis, John Addington Symonds, Auguste Forel, and Eugen Steinach, as well as the lesser-known work of Richard Burton on Sotadic Zones, geographical areas that foster the development of homosexuality. Kahan then traces this environmental model of sexuality in Thomas Mann’s Death in Venice (1912), arguing that it “roots homosexuality in the competing epidemiological regimes of anthropologia sexualis’s humoralism and scientia sexualis’s germ theory,” providing “rich models for theorizing sexuality as climactic on the one hand and microbial on the other” (47). As Kahan maps a stabilization of the body away from anthropologia sexualis to a more stable germ theory, he also points out a second stabilization of the body: in Mann’s representation of an older man’s desire for a younger boy, no longer is the body understood as passing through various sexual stages as it ages, but instead the demand on sexual desire to be constant presents a shift away from age difference to age similitude.
In the third chapter, “Magia Sexualis, Sexual Subjectivity, and the Wilfulness of Sexual Aim,” Kahan argues that “conceptions of magic, sorcery, witchcraft, and the occult have influenced constructions of sex and sexuality to a much greater extent than has been realized in the existing scholarship” (23). Borrowing a term from Paschal Beverly Randolph, a nineteenth-century African American sexual magician, he calls this the magia sexualis, highlighting the historical entwinedness of sexuality and magic through mesmerism, genius, second sight, occultism, and spiritualism. Kahan discusses this magia sexualis with reference to two novels, Ludwig von Reizenstein’s The Mysteries of New Orleans (1854-1855) and George du Maurier’s Trilby (1894). The Mysteries of New Orleans presents a model of sexuality centred on elective affinity, a form of erotic organisation that is not defined through object choice but is enabled by magic and prophecy, an erotic organisation which is only gradually internalised. Trilby presents a variation of this magia sexualis by showing sexuality to be aim-based but objectless, directed through mediumship. Kahan argues that without definitive object choice, sexuality is essentially non-subjective, because “a sharp differentiation between subject and object is necessary for the creation of sexual subjectivity: having an object is a precondition of becoming a subject” (75). Finally, Kahan argues that Randolph’s magia sexualis, which rejects mediumship in favour of will and agency, offers one of the earliest theories of sexual personhood and subjectivity, where the “magical operation of desire—alighting upon particular objects in ways that pass understanding, that feel supernatural or alchemical or just plain enchanting—serves to codify their difference” (84), resulting in an object-subject-based sexuality.
Chapter 4, “Sex in the Age of Fordism: The Standardization of Sexual Objects,” discusses how industrialization takes the shape of sexual etiology. This chapter focuses on Antonio Gramsci’s and Sherwood Anderson’s understandings of Fordism as a standardising force of sexual object choice, and Anderson’s subsequent critique of the standardization of the human under Fordism. In Winesburg, Ohio (1919), Anderson “locates consumer and sexual objects at the center of modern fields of desire and imagines the inhabitants of the small Ohio town to enact nonindustrialized and nonstandardized sexual pleasures” (24). One of these sites of sexual pleasure which Kahan determines in Anderson’s work is America’s romanticized landscape, with its varied and multiple sources of pleasure. Another focuses on the representation of hands and touch as non-industrialized, vague, and therefore not clearly delimited forms of pleasure. Kahan concludes this chapter by arguing that industrialization speeds up the standardization of sexuality and its congealment into an object-based sexuality.
The final chapter, “Volitional Etiology: Toward a Weak Theory of Etiology,” discusses etiology’s temporal order, focusing on a set of etiologies that confused sexologists because they appeared volitional rather than environmental, somewhere between choice and compulsion: gambling, smoking, celibacy, criminality, opium, and others. According to Kahan here, a strong theory creates one set of events with a single causal chain, whereas weak theory makes space for narrative profusion and possible coexisting consequences. As he further argues in this chapter, “etiology in its weakness will enable us to loosen the totalizing force of sexuality’s seizure and inhabitation of the body” (101). With reference to alcoholism as a case study, this chapter argues that sexologists grappled with etiological priority, where alcoholism could occupy a range of sequential positions: “alcoholism can induce homosexuality, be simultaneous with it, follow from it, or can make one sexually attractive” (109ff). As Kahan then argues, this shows that no form of sexuality should be considered derivative or secondary, because the co-existence of various sequential positions shows that sexual etiology is fundamentally fictional. Sexuality, Kahan argues, has to be understood as an assemblage (113). In a statement concluding his final chapter, Kahan argues that “even as historical forces are solidifying and delimiting the sexual subject—in relation to constancy (chapter 1), boundedness (chapter 2), agency (chapter 3), and standardization in relation to objects (chapter 4)—volition scrambles sequential unfolding, pluralizing sequences” (114).
Kahan’s chapter-length conclusion, entitled “After Sedgwick: The Gordian Knot of the Great Paradigm Shift,” summarises how his investigation into the history of Sedgwick’s Great Paradigm Shift informs a pressing debate in the study of historical sexuality, namely the supposed incommensurability of two bodies of literature, one claiming that homosexuality emerged in the seventeenth century and the other claiming its emergence for the nineteenth century. The Book of Minor Perverts puts these into useful dialogue in two ways. First, by looking at the seventeenth-century figure of the molly, Kahan argues that this figure anticipates the idea of congenitality and an innateness of sexuality. Sometimes the molly’s sexual morphology appears to be legible on the body, or it seems as if possessive categories emerge from sexual subjectivity. As Kahan puts it, “the ingredients of homosexuality are all there; they just haven’t been baked together” (124). More broadly speaking, Kahan “understand[s] congenitality as one of ‘the conditions of emergence for’ homosexuality even if it does not itself constitute that emergence. To put this differently, sexual self-possession and congenitality unexpectedly precede sexuality” (124). The second contribution that The Book of Minor Perverts makes tothe historical debate about the emergence of homosexuality is its emphasis on the intersectionality of object choice, where race, class, gender, and age all relate to sexual object choice. With reference to age, for example, Kahan argues that “men’s definitional shift from being defined in relation to boys to being defined in relation to women cements both the gender differentiation for the homo/hetero binary as well as its age consistency” (126).
Kahan concludes this final section with a summarising account of the pre-history of the Great Paradigm Shift, or how the hetero/homo binary came to take on greater authority: the idea of object choice as an organising principle of sexuality arose in the second half of the nineteenth century, but it did not catch on for a long time, until the early twentieth century, when congenitality and naturalness as models for thinking about sexuality settled in the 1930s. Acquired models of sexuality, however, continued to exist during this period:
Behaviors, acts, beings, diseases, environments, circumstances, historical forces, identities, embodiments, perversions, and varieties of gender that from a twenty-first century vantage might appear to be outside of sexuality’s domain or appear on its margins are brought to its center. Historical etiology makes clear that we need a sexual historiography that is capacious enough to accommodate approaches to sexuality that are simultaneously continuist and open to historical alterity. This, then, is the promise of etiology—that we can bring into focus the etiolated, overlapping, unrationalized, diachronic, synchronic, collaged, messy contours of sexuality. (137)
Etiology as a framework for thinking sexuality brings out various competing narratives, but etiology as a conceptual approach to the history of sexuality can show us how diverse sexual narratives unfold.
The Book of Minor Perverts contributes a range of exciting new findings to the study of historical sexology and the history of sexuality more broadly. One of the major contributions of this book is to think sexuality beyond—or before—identity in order to illuminate how sexual subjectivity emerged. Untangling sexuality from subjectivity allows us to pay attention to sexuality’s entanglement with other forces, here environment, geography, temporality, magic, volition, and industrialisation, and to sexuality’s intersectional entanglement with race, class, age, and gender. Paying attention to these “messy contours of sexuality” and their diverse sexual narratives also amounts to a second contribution of The Book of Minor Perverts: it allows Kahan to introduce new literary texts into a discussion of sexuality’s emergence. The book pushes and extends the archive of sexuality and sexology beyond its known limits, adding hitherto neglected literary sources and sexological thinkers, for example sexual magician Paschal Beverly Randolph, as well as developing his historical etiology as a novel critical framework for thinking about the emergence of sexuality, which breathes new life into analyses of canonical texts, for example Mann’s Death in Venice. A final and major contribution of Kahan’s monograph is that it shows the difference literary studies and queer theory can make to the study of historical sexology and, conversely, how an investigation into the moment—or, as Kahan’s book shows, multiple moments—of the emergence of sexuality can make historical etiology a useful tool for queer theory and literary study.
Studies of sexology from a literary rather than an exclusively historical point of view are still rare and Kahan’s study shows the richness of this approach to scholarship on historical sexology. However, to the historically minded reader, some aspects of Kahan’s work might appear irksome. Kahan’s book ostensibly focuses on a US context, but his analysis throughout often draws on a variety of sources from Germany, Austria, and Britain—places where vibrant sexological exchange took place. This is important, especially in the context of recent scholarship which emphasises the global nature of sexual sciences, but it could have been useful to offer a more direct comment on how his argument about the emergence of sexuality is specific to the US, and to contextualise certain concepts in their linguistic and national background. ‘Race,’ for example, had a different meaning in Germany than it did in Britain or the US during the period discussed in Kahan’s book.
Kahan’s investigation into sexual etiologies will influence many scholarly discussions in the future. It speaks to recent research about the possibilities of thinking sex beyond the subject and in environmental terms, where it stands in dialogue with Greta LaFleur’s excellent monograph The Natural History of Sexuality in Early America. I also expect that it will further encourage literary approaches to the study of historical sexology, where it will expand the sexological archive in new and necessary ways. Finally, Kahan’s discussion of sexuality’s intersectional entanglements, in particular with age, speaks to recent scholarship in the history of sexology highlighting the entanglement of concepts of age and sexuality. Overall, The Book of Minor Perverts is an intelligent, sharp, and exciting book and I expect that it will be recognised as a significant study in the history of sexuality, the study of historical sexology, queer theory, modernist literature, and medical humanities.
 See Kate Fisher and Jana Funke, “Cross-Disciplinary Translation: British Sexual Science, History and Anthropology,” in Heike Bauer, ed., Sexology and Translation: Cultural and Scientific Encounters across the Modern World (Philadelphia: Temple University Press, 2015), 95-114; Heike Bauer, English Literary Sexology (Basingstoke: Palgrave Macmillan, 2009); Anna Katharina Schaffner, Modernism and Perversion (Basingstoke: Palgrave Macmillan, 2012); and Ina Linge, “Sexology, Popular Science and Queer History in Anders als die Andern (Different from the Others),” Gender & History 30.3 (November 2018): 1-16.
 Eve Kosofsky Sedgwick, Epistemology of the Closet (Berkeley, Los Angeles, and London: University of California Press,  2008).
 See Heike Bauer, ed., Sexology and Translation: Cultural and Scientific Encounters across the Modern World (Philadelphia: Temple University Press, 2015); and Veronika Fuechtner, Douglas E. Haynes, and Ryan M. Jones, eds, Towards a Global History of Sexual Science, 1880-1960 (Oakland: University of California Press, 2018).
 Greta LaFleur, The Natural History of Sexuality in Early America (Baltimore: Johns Hopkins University Press, 2018).
 Kate Fisher and Jana Funke, “The Age of Attraction: Age, Gender and the History of Modern Male Homosexuality,” Gender & History 31.2 (July 2019): 266-83.