The world of charlatans is a world of constantly shifting borders and redefinitions, a world of crossed lines and pushed boundaries. Can one even speak of “the world” of charlatans in the singular, when the examples we are given to read in this volume reveal such great diversity that they seem to defeat any attempt to define common traits, as Roy Porter (Reference Porter1989) tried to do in his time? Certainly, commercial interests and the lure of a quick and easy profit seem to have motivated some charlatans. Certainly, the universal effects of the nostrum or (psycho)therapeutic procedures were often put forward as a commercial argument. Certainly, many had an itinerant career; but this was not always the case. In fact, these traits are not shared, and the main reason is probably that, aside from a very particular context in early modern Italy, the qualification of charlatan was not claimed by the actors themselves, but was attributed to them by others, be they contemporaries or later historians. These features are therefore only common if we understand them as stigmataFootnote ¹ attributed to charlatans by those who wish to distinguish themselves from them or to draw a line between orthodoxy and heterodoxy.

In the eyes of those who denounce them, charlatans share a major common trait: they are, first and foremost, fraudsters. They lie about their qualification or the results of their practice; they sometimes perform tricks that resemble magic. None is considered truthful and earnest. At best, so-called charlatans defraud in an unconscious manner, as has been argued about some talking horse trainers (see Gethmann, in this volume) and some mediums like Eusapia (see de Ceglia and Leporiere, in this volume), and more notably Helen Smith, according to Théodore Flournoy’s and William James’ interpretations (Cefali, Reference Cefali1983; Trochu, Reference Trochu2018).

The issue of fraud is of particular interest because it highlights what I would define as situations of minimal acculturation, instances where culturally and socially distant actors meet and have to engage in a dialogue using partly common language and procedures, and where hybridization occurs between “high” and “low”, dominant and dominated, popular and scholarly. I borrow this notion from modern cultural anthropology and sociology, following the canonical definition of Robert Redfield, Ralph Linton, and Melville J. Herskovits, with special emphasis on the collateral nature of the changes: “Those phenomena which result when groups of individuals having different cultures come into continuous first-hand contact, with subsequent changes in the original cultural patterns of either or both groups” (Redfield, Linton, and Herskovits Reference Redfield, Ralph and Herskovits1936, 149).

Most of the articles gathered here demonstrate the centrality of the issue of fraud in the debates on charlatanism and the importance of the procedures put in place to demonstrate the point of view of one or the other. One could perhaps compare these assessments to those carried out in the nineteenth century on Catholic visionaries and apparitions. As historians of religion have shown, not only the opponents of the reality of miracles, but the Catholic Church itself set up investigative procedures (Forster Reference Forster1989; Smoller Reference Smoller2011; Vidal Reference Vidal2007). The latter, as in the case of the Medical Examination Office for miraculous healings at Lourdes (Ogorzelec Reference Ogorzelec2014; Harris Reference Harris1999), were in no way different in form from those carried out by doctors who did not believe in the possibility of such healings. Such is also the case with mediums or with talking horses, when believers (often gathered in psychical research associations) and sceptics could adopt similar modes of expertise. Such procedures are instances of acculturation, allowing us to see it in progress, playing at different levels. As in the case of the medium Eusapia, some so-called charlatans seemed to be relatively passive and only submitted to a scholarly expertise to which they did not pretend, while undoubtedly defying it since, in many cases, the fraud could not be proven by the experts.

The suspected “charlatans” or mystifiers indeed often mastered enough skill and/or enough belief to resist exposure. Although there were many signs of fraud, Eusapia defied the observers, probably using means that came from the same practical knowledge of the psychology of attention (what we could call a spontaneous psychology of attention) that prestidigitators and pickpockets mastered. Her skills probably improved as she became more familiar with the observation procedures to which she was subject. In those cases where the social and cultural distance between the subject under evaluation and the evaluators is maximal, intermediaries, with their own agendas, frequently intervened. The commercial agents, impresarios, or managers who promoted the careers of charlatans (men, seldom women, while charlatans were female or male) for economic reasons, as well as the amateurs, who exhibited charlatans in order to prove their own theory and to increase their social position, can be considered as go-betweens between different cultural and social worlds (Schaffer et al., Reference Schaffer, Roberts, Raj and Delbourgo2009). They groomed their charlatan-associates and taught them how to behave in front of a scholarly or bourgeois audience, playing the role of translators of social and cultural norms. They were also often instrumental in the media coverage of charlatanism, and they helped create a hybrid space between the world of science and the world of the press, a long-term characteristic of charlatanism which the cases studied in this volume clearly highlight.

In other cases, the so-called charlatans engaged themselves in an experimental approach and met sceptical academic experts on their own ground. Doing so, they demonstrated a minimal knowledge of academic norms, setting or mimicking laboratory experimental practice and using sophisticated instruments. In such cases, charlatanism could be a transitory condition in an upward social and professional trajectory that might end at the university or museum (Podgorny Reference Podgorny and Kominko2015, Reference Podgorny2017). The retired schoolteacher Wilhem von Orsten, the first trainer of the talking horse Clever Hans, had probably a mainly pedagogical agenda and wanted to demonstrate that horses could be educated like children. He did not personally engage in an experimental procedure, but submitted his horse to psychological experiments carried out by university psychologists. He became himself unknowingly the main subject of the experimentation, and in this way he resembles the mediums submitted to external expertise. Such is not the case with the second owner of the horse, Karl Krall, a member of a family of jewelers who set up his own laboratory, using expensive modern devices such as the cinematograph and the telephone, and had his own scientific agenda in animal psychology and psychic research. He founded his own institute, outside academia, and lived the life of an experimental scientist. The same issue (can horses talk?) allowed the botanist Joseph Banks Rhine to become an experimental psychologist at Duke University and to introduce psychical research into the psychology department. In such cases, charlatans can be compared to amateurs, with whom they share many traits (Guillemain and Richard Reference Guillemain and Richard2016).

Like some amateurs, charlatans work on the margins, and challenge the boundaries of orthodoxy, which they help to blur and shift. At the end of the nineteenth century, a specific French expression was coined to designate the margins of the undecidable between the rational and the irrational, and between the natural and the supernatural, that of “merveilleux scientifique,” scientific marvelous (Durand de Gros Reference Durand (de Gros)1894; Plas Reference Plas2000). In the contemporaries’ views, this space was properly intermediate, and it is now situated on one side or the other only by anachronism. It was therefore not surprising that rationalists and occultists, professionals and amateurs, sincere actors and crooks – who could be equally divided between the two camps of believers and non-believers – rubbed shoulders in this in-between. Such a space was made possible by the belief in the powers of science and was, one might say, the result of “hyper positivism.” The proponents of positive science at the end of the nineteenth century were sometimes great promoters of psychic studies and alternative physical explanations. They did not perceive the phenomena they were studying as belonging to what we now call parapsychology or pseudo-science, but rather as a frontier to be conquered by science, where rational, positive explanations, in terms of fluids, rays, or vibrations would be found (Bensaude-Vincent and Blondel Reference Bensaude-Vincent and Christine2002; Oppenheim Reference Oppenheim1985; Plas Reference Plas2000). This “scientific marvelous” was also an in-between: between science and fiction (Hopkins Reference Hopkins2018), between academic and the media culture, and between disinterested practice and trade. It can therefore also be described in terms of acculturation, as it was a space where hybridization occurred between popular (or mass) and high culture. So understood, charlatanism brought fragments of science to the popular audience and fragments of popular culture to the scientific audience in ways that were not solely confrontational, but also fostered cross-fertilization. As the papers in this special issue demonstrate, the categories of popular and scholarly, of high and low, do not function operatively when historians attempt to describe the lives and trajectories, the theories and practice of charlatans.

The “scientific marvelous” had a key function in bringing science to the media and to mass print-culture. The role played by the general press, by science popularizers and journalists, and by advertisement techniques is evident in all the cases studied in this volume. It points to another aspect of charlatanism that I would like to emphasize, that is its modernity. Contrary to what has sometimes been asserted, the science of charlatans is not inherited from the past or timeless. On the contrary, it appears as quintessentially modern, in that it syncretizes elements of a popular culture that we now know is not “without history” and elements borrowed from the cutting edge of the modernity of its time.

As the article on François Vincent Raspail’s popular medicine points out, the charlatan is a man or woman of his or her time, situated in a specific social, political, and cultural context. So much so that, in my point of view, there is no such thing as a “longue durée” of charlatanism. Indeed, most of the papers gathered in this issue show that the late nineteenth and early twentieth-century charlatans were not the same as their earlier counterparts. In medicine for example, they were now linked to the modern pharmaceutical industry, and their practice questioned the boundary between medicine and business in a time of reorganization of the professions. As shown in this issue, the promoters of cundurango in the 1870s were not similar to the “piss-work” practitioners of the seventeenth century. Even though they were medical doctors equally confronted by accusations of charlatanism, their medical claims and the accusations from their critics did not raise the same issues. Raspail’s popular medicine reveals another aspect of the modernity of charlatanism, as his theory addressed topical political issues rather than economic ones. His medicine challenged the place of medical science and the role of physicians in the new democracy promoted by mid-nineteenth-century French republicans.

Just like the economic, social, and political conditions in which charlatanism takes its specific form, the fields most open to charlatans also change according to the development of scientific disciplines. Around 1900, new ways of understanding the body as a machine consuming energy and producing work paved the way for new research, but also for a new type of shows and entertainments displaying extraordinary cases of endurance, be it of hunger or extreme physical strain (as in the dance marathons depicted in Horace McCoy’s 1935 novel They Shoot Horses, Don’t They?). Fasting artists developed on such a ground, and unintentionally helped further our understanding of nutrition. At a time when vivisection and cruelty to animals were strongly criticized, fasting performers provided live experiments for physiologists, were sometimes associated with physicians, and drew some of their fame from medical observations. Their performance can therefore be analyzed as an instance of syncretism between the popular entertainment provided by music halls and experimental physiology. In the same period, neurology and psychology were also favorable grounds for the emergence of actors who could be qualified as charlatans. Through their practices, they questioned scientific issues that were then of great topicality about the capacities of the human mind, the influence of mind on the body, and the human-animal boundary. These so-called charlatans – although the term was not always applied to them – were therefore at the cutting edge of the modernity of the science of their time, which they sometimes helped to advance, as in developmental psychology and communication sciences.

The charlatans and/or their managers who produced their own theoretical discourses could be modern in still another way, by invoking “modernity” as an advertising argument (in order to sell “novelties”) or to increase the credibility of their theories. Sometimes, as in the case of Raspail and of many promoters of “alternative” medical theories (for example, Faure Reference Faure2018), they reversed the argument, accusing orthodox professionals of conservatism and rejecting them as promoters of outdated or outmoded science. In these cases, charlatans could appear more modern and less bound by tradition than mainstream practitioners.

In order to demonstrate this modernity, those heterodox practitioners could rely on theoretical explanations based on the most recent orthodox scientific theories. Around 1900, radio waves and X-rays were particularly fashionable. The first ones were used, for instance, as an explanatory model for medical radiesthesia in the interwar period, and the physicist Edouard Branly, who was at the heart of the research on radio conduction in France, was closely linked to the first networks of medical dowsers. Heterodox practitioners could also choose to demonstrate their modernity by means of modern technology. By 1900, they used the latest viewing and recording devices, such as photography, cinematograph, phonograph, telephone, etc. In such cases, their modernity was a syncretism of technical progress and the new visual and audio mass culture of the twentieth century.

Neither old nor modern, neither popular nor scholarly, charlatans are always in-between, just like the “scientific marvelous” in which they flourished. They act as intermediaries and translators, favoring two-way exchanges between tradition and novelty, between popular and learned cultures, between publicity and secrecy, and creating spaces for syncretism and acculturation. They also act as revealers, in the chemical meaning of the world, of the ways in which orthodoxy and heterodoxy, low and high, are differentiated at a particular time and place, but also of the ways in which science interacts with society. Many authors in this volume highlight the first point, emphasizing the epistemological usefulness of charlatans; fewer stress their usefulness for a more social and political history of science.