As early as 1620, Francis Bacon proposed a framework for the treatment of monstrosity that differed radically from earlier “studies” of monsters. In contrast to the more common compendiums of superstition-infused monstrous iconography (the most famous example being Ambrose Paré’s Des monstres et prodiges ), Bacon appealed to a new generation of scientists to create “a compilation, or particular natural history...of all monsters and prodigious births of nature.” 1 Viewing monstrous births not as omens or portents, Bacon argued that the monster is a point of reference that allows the naturalist to identify the overreaching regularity of the rest of organic life: “He who is acquainted with the paths of nature, will more readily observe her deviations; and vice versa, he who has learnt her deviations, will be able more accurately to describe her paths” (p. 159). This transformation of the monster into a benchmark for the rational study and understanding of the universe was appropriated and expanded upon by d’Alembert in the Encyclopédie’s “Système des connaissances humaines” (1751). Paraphrasing Bacon, d’Alembert writes:
Il est inutile de s’étendre sur les avantages de l’histoire de la nature uniforme. Mais si l’on nous demande à quoi peut servir l’histoire de la nature monstrueuse, nous répondrons à passer des prodiges de ses écarts aux merveilles de l’art; à l’égarer encore ou à la remettre dans son chemin; & surtout à corriger la témérité des propositions générales, ut axiomatum corrigatur iniquitas. 2
In accord with Bacon’s rejection of any preexisting authority, d’Alembert valorized a supposedly disinterested inquiry into monstrosity; freed from the domain of metaphysical speculation, attached to the realm of anatomy, the study of deviant births should—according to the geometrician—provide an excellent means of reorienting man’s understanding of nature’s order.
Historians of thought have long underlined the epistemological shift that the concept of monstrosity underwent during the eighteenth century. Although the era’s understanding of embryology allowed only incomplete speculation on the etiology of anomalous formations, Enlightenment physicians and naturalists progressively detached dicephalous infants and Siamese twins from the realm of superstition. This evolution [End Page 1] of the monster from a transgressive phenomenon to a biological anomaly is echoed in the definitions of monsters in the century’s dictionaries. In late seventeenth- and early eighteenth-century definitions of monstrosity (including Antoine Furetière’s Dictionnaire universel  and the Dictionnaire de Trévoux ), the monstrous birth is prodigious in that it disobeys the very laws of nature. Identified less by anatomical criteria than by the visceral reaction one has in perceiving it, the monster is a “prodige qui est contre l’ordre de la nature, qu’on admire, ou qui fait peur.” 3 By the mid-eighteenth century, the Encyclopédie (1751–72) reflects a more rationalized understanding of monstrosity. Although deformed infants are still identified as contre l’ordre de la nature, the lexicon used to describe the monster becomes increasingly demystified; Formey quite lucidly interprets the monster as an “animal...avec une structure de parties très différentes de celles qui caractérisent l’espèce des animaux dont il sort” (“Monstre,” Encyclopédie, 10:671). Far from supernatural or extraordinary phenomena, writes Jaucourt, such productions are quite simply “des naissances monstrueuses d’hommes ou d’animaux qui effrayoient alors les nations entières, & qui servent aujourd’hui d’amusement aux Physiciens” (“Prodige,” Encyclopédie, 13:422). 4 By the time that the Supplément à l’Encyclopédie article “Monstre” appeared in 1777, this measured view of monstrosity had become the norm: not only does the article’s author, La Fosse, mock the interpretation of the monster as an omen, he self-righteously separates his era’s more progressive understanding of monstrosity from that of previous times, castigating those people who “[ont] souvent allumé des bûchers pour exterminer les malheureux que l’opinion publique, si souvent téméraire & cruelle, déclaroit auteurs d’une chose impossible.” 5 While it would be wrong to argue that the birth of a monster was greeted with clinical detachment by...