Writing in the seventeenth century, Descartes pondered whether all his experiences might be the fabrications of a malicious demon intent on deceiving him. An updated version of his argument posits that I am a brain in a vat in the laboratory of a scientist who is likewise generating all my experiences. Both scenarios reflect the supposition that the brain is the locus of our personhood and subjectivity, as does the fact that, as neuroscientist M. Gazzaniga points out, while we are willing to receive heart, kidney or liver transplants, we would not consider brain transplantation as a remedy for brain damage since, rather than the recipient acquiring a new brain, the donor would acquire a new body (Gazzaniga, The Ethical Brain [2005], p. 31). Following F. Vidal, W. refers to this identification of the human self with the brain as ‘cerebral subjectivity’ (p. 4; cf. Vidal and F. Ortega, Being Brains: Making the Cerebral Subject [2017]). But whereas Vidal's history of cerebral subjectivity jumps from Galen to Descartes in the belief that the intervening centuries saw little interest in the relation between the anatomical brain and human personhood, W. shows that Christian writers in late antiquity made scientific knowledge of the brain an essential component of their account of human personhood, both anticipating cerebral subjectivity and paving the way for it, as well as referring to the brain's physical properties when adjudicating pastoral dilemmas and in order to establish their authority as physicians of the soul by projecting medical expertise. In the course of this study we see how their engagement with scientific knowledge of the brain forced them to confront the implications of such knowledge for theological constructions of the soul: if the material brain is the organ of the immaterial soul, how are they connected? Does the brain somehow contain the soul, and, if so, can it also constrain it? Can damage to the brain compromise the soul's integrity? Might increased knowledge of the brain render the soul theoretically otiose?

The book comprises an introduction, seven chapters and a conclusion. W. starts from the ancient debate regarding the physical location of the soul's ruling faculty. While Aristotle and the Stoics favoured the heart (‘cardiocentrism’), Plato, Galen and other medical writers favoured the head (‘encephalocentrism’). So too did the majority of late antique theologians despite the fact that, as W. points out, cardiocentrism has scriptural warrant whereas encephalocentrism does not. Augustine responds to this problem by interpreting biblical allusions to the heart as the locus of agency and personhood, for example the injunction to love God with all our heart, as metaphorical (On the Trinity 10.7, citing Deut. 6:5).

Chapter 1, ‘The Circulation and Performance of Medical Knowledge in Late Antiquity’, explores the social and intellectual contexts in which Christian preachers, acting as iatrosophists, ‘medical orators’, deployed and disseminated medical expertise and in doing so established their authority as physicians of the soul. It includes a discussion of Macrobius’ Saturnalia and a preliminary survey of Gregory of Nyssa's On the Constitution of the Human Being. Chapter 2, ‘The History of the Brain in Ancient Greek Medicine and Philosophy’, begins with Presocratic and Hippocratic understandings of the brain and proceeds via Plato and Aristotle to the third-century bce medical writer Praxagoras of Cos, the Alexandrian anatomists Herophilus of Chalcedon and Erasistratus of Cos, the Stoic philosopher Chrysippus, and Galen of Pergamon. Chapter 3, ‘The Invention of Ventricular Localization’, focuses on how late antique theologians deployed the medical theory of the localisation of mental faculties in the ventricles of the brain. Against the conventional view that Christian thinkers discounted the material substance of the brain by supposing the ventricles to be the location of an immaterial soul, which was responsible for all perception, cognition and agency, W. argues that Nemesius, Augustine and Gregory of Nyssa (here W. returns to On the Constitution of the Human Being) conceived the relationship between the immaterial soul and the material brain in instrumentalist terms, according to which the soul acts through the brain by ‘playing’ it like a lyre such that mental activity involved the interplay of airflow, hollow structure and material substance. The turning point from instrumentalism to the metaphors of containment that characterised medieval cell theory comes in the writings of the Byzantine medical author Theophilus Protospatharius.

Chapter 4, ‘The Governing Brain’, explores how Christian preachers and theologians anthropomorphised the brain as the agent of governance. W. traces the development of this trope from its antecedents in Heraclitus, Plato and Alcinous / Albinus, through Gregory of Nyssa's On the Constitution of the Human Being, to John Chrysostom, and contrasts Ambrose of Milan's casting of the head rather than the brain as governor. An extension of the metaphor of the brain as governor saw Christ likened to the brain of the ecclesial body, meaning that a familiar medical concept was used to illumine an unfamiliar theological concept. Chapters 5, ‘The Rhetoric of Cerebral Vulnerability’, and 6, ‘Insanity, Vainglory, and Phrenitis’, look at how the brain's physical vulnerability was invoked in the service of pastoral agendas. The brain's softness made it susceptible to damage and intoxication, which could impact upon the capacity for reason and self-control, and thus for virtue and so potentially even for salvation. At the same time its vulnerability reflected that of the human person in their dependence on God, and keeping this in view required establishing limits to ascetic practice, which, when violated, were liable to lead to madness. The sources W. considers include John Chrysostom's warnings against drunkenness and luxury and Augustine's use of the rhetoric of insanity in his campaign against the rigorist and heretical Donatists.

Chapter 7, ‘Humanising the Brain in Early Christianity’, concludes the book with an especially thought-provoking discussion, which takes as its starting point the fact that, while Christian authors routinely compare various other parts of the human body to their animal counterparts to argue that human anatomy is uniquely fitted to support rational governance, they never compare human brains with animal brains. Describing this absence as ‘challenging to explain’ (p. 173), W. proceeds to explore how Christian authors invested in the brain as a conceptual tool in their arguments for human exceptionalism and hegemony and thus paved the way for cerebral subjectivity understood as a post-Enlightenment political ideology whose effects are still very much with us today.

A clarification regarding Evagrius: W. describes vainglory as ‘a passion linked to hallucinatory perceptions of God and of oneself’ (p. 157), but for Evagrius episodes involving hallucinations of God are only one of the many forms that vainglory can take (cf. e.g. Praktikos 30–2), and the perceptions of oneself it involves are fantasy images rather than hallucinations. It can also be noted that, unlike Augustine and despite being no stranger to metaphor and allegory, Evagrius took scriptural references to the heart literally by associating the nous, the locus of personhood and agency, with the heart (cf. Kephalaia Gnostika 6.84) and only the derivative faculty of dianoia with the brain.

This is a valuable study, carefully and comprehensively researched, beautifully written and well produced, of importance to many fields including the history of science, psychology, western culture and Christianity. It deserves a wide readership.