Recent work in science studies has argued that the brain is socially constructed in two, mutually constitutive ways. Firstly, the brain as a structure is plastic, changing throughout a lifetime in relationship to the social environment. Secondly, how the brain is understood and imagined changes across time and geographical space, which itself informs the brain's processes. Jess Keiser's Nervous Fictions is a fascinating and detailed examination of the second of these two ideas of the socially constructed brain, focusing on English literary representations of the brain as part of the mind-body problem that preoccupied natural philosophers and physicians during the Enlightenment period. Crucial to Keiser's discussion is the concept of the “nervous fiction,” the figurative language that writers used to describe the workings of the mind and its relationship to the body. These “nervous fictions” included metaphors that likened the brain to a castle, theater or watch, or a whole imaginative realm of animal spirits acting as servants and soldiers of the sovereign mind. Examining these literary fictions of the brain, Keiser argues, is key to understanding eighteenth-century ideas of the psyche, which in turn “tell us something important about its values, philosophy, and aesthetics” (26).

Keiser's finely woven, intricate study of Enlightenment ideas of the brain pays close attention to figurative language in the construction of scientific knowledge. Each chapter of Nervous Fictions is a deep dive into one Enlightenment literary figure and their intellectual world, showing how their ideas developed and departed from ancient and Cartesian philosophy, and explicating their use of figurative language in an attempt to understand and explain the workings of the mind. In chapter 1, Keiser considers the late seventeenth-century physician-philosopher Thomas Willis’ conceptualization of the brain as the sovereign center that commands and receives the animal spirits to whom he attributed considerable agency and affect. Keiser pays close attention to Willis's ambivalences about the use of poetics and “fancy” in his neuroscientific project, ambivalences that reveal the tensions at play in any attempt to render the brain and organ of the mind (37). It is this tension that reveals Keiser's wider point about the role and importance of figurative language in changing conceptualizations of the brain: “In order to understand the brain as an organ that produces the mind (as opposed to treating the brain as a mindless body part like the heart or spleen), he [Willis] must first figure brain matter as inherently thoughtful or else face an explanatory gap” (39). Keiser develops this discussion of the problem of matter, mind, and agency in her second chapter on Margaret Cavendish's images of the brain. For Cavendish, all matter is thinking, albeit in various degrees, which not only challenges where the brain and nervous system reside but fundamentally requires us to question what thought is, and how (and whether) it can be described at all. As Keiser illustrates in chapter three, Cavendish's challenge to those physicians, who believed they could describe the workings of the mind through dissection of the brain, resonated with some parts of Locke's An Essay Concerning Human Understanding (1689). Locke's opposition to the reduction of mind to matter led him to argue for a focus on thoughts themselves. Yet his own brief description of madness as a lack of ability to control the association of ideas looked to the brain as matter and relied on the figurative language of animal spirits. In an interesting move that links Cavendish's anti-empiricism to Locke's advocacy for describing only what can be seen, Keiser shows how neuroscience itself is positioned at a conceptual impasse that can only be bridged through the use of nervous fictions.

Locke's refusal to countenance the possibility of ever fully knowing the connection between mind and matter was part of wider epistemological debates over what it was possible to know about the mind and the self. In the final three chapters, Keiser turns to Addison's Spectator and the Scriblerians’ grappling with questions of the brain, the relationship between matter and meaning, and the limits of scientific knowledge. Like Cavendish earlier, these satirical writings mocked the assumption that dissection of the brain could uncover the truth about neural processes and “witness the mind at work in the nerves” (155). At the same time, Keiser argues that Memoirs of the Extraordinary Life, Works, and Discoveries of Martinus Scriblerus (1714–27) tells the story of the development of neuroscience from the ancient to the modern, to the Cartesian understanding of the mind-body dualism, to skepticism of their own times. Keiser elaborates on this trajectory in the final two chapters, on Laurence Sterne and James Boswell, showing how Sterne's A Sentimental Journey through France and Italy and Boswell's “The Hypochondriack” each illustrate the transition in neuroscientific representations from the hierarchical conceptualization of the brain as the commanding center of an army of animal spirits to an emphasis on the harmonious relationship between physiological, as well as social, organisms. More importantly for Keiser's project, the fallacy of the brain as a knowable object that would reveal the inner workings of the mind had been exposed. Boswell's use of the metaphor of the mind as a closed clock both illustrated the impossibility of bridging the gap between matter and mind, but also the reliance of neuroscience on “nervous fictions” that continue to this day.

By the end of the early nineteenth century, the mechanistic ideas of the brain as the control center of the body with the pineal gland at its core had been eclipsed by an idea of the brain as part of a wider network of both body and society. The new vitalist physiology understood the role of the brain as rationalizer of events and actions taking place outside of itself, whether within the body or beyond it, in society. Keiser's detailed mapping of this complex transition is fascinating and the argument for the role of “nervous fictions” compelling. As with all good scholarship, I was left wanting to know more: What is significance of this transition in ideas of the mind and body, and how does it relate to the work of Charles Taylor or Dror Wahrman on selfhood during this period? What do these literary fictions of the brain tell us about changing “values, philosophy, and aesthetics” (26)? How might they elucidate the changing ways in which British elites of the Enlightenment imagined “the human” in an era so fundamentally shaped by colonial encounters with difference?