Homo cerebralis: Der Wandel vom Seelenorgan zum Gehirn (review)

The neurosciences have come to dominate the spaces of knowledge and modes of representation in the human sciences. Almost everything human falls under the spell of the brain in modern scientific culture: the human faculties and the phenomena of mental life, the emotions and the genesis of language, the differences of sex, race, and intelligence. In Homo cerebralis Michael Hagner brilliantly shows how the success of the neurosciences, and especially the concept of localization, from the 1860s onward, was the late outcome of a major epistemic shift from Descartes’s dualism of body and soul to the moderns’ world of observable, countable, and quantifiable phenomena. He puts this story of a scientific conquest in a broad historical perspective, spanning the late eighteenth century to 1874 and covering developments in the German-speaking countries as well as in France and England. A reshuffling of the spaces of knowledge during the first decades of the nineteenth century prepared the ground for this shift that encompassed heterogeneous discourses of the soul and brain. Hagner investigates these processes at their various disciplinary locations and thus demonstrates how the brain became central, not only for neuroanatomy and medicine, but for the brain sciences.

In an intriguing chapter on Samuel Thomas Soemmerring Ueber das Organ der Seele (1796), Hagner argues that until its publication the search for the organ of the soul remained a Cartesian project seeking the bodily center of immaterial human intellectual activity. Nearly simultaneously, Franz Joseph Gall—the neuroanatomist best known as the founder of phrenology—turned the brain and skull into the representational space of the soul, thus breaking the control of philosophy over such questions and opening an epistemically new era. Gall stipulated a strictly functional correlation between psychical phenomena and brain structures, thereby discarding the old concept of the philosophical center and a biological periphery.

Hagner’s contextualization of the origins of modern neurosciences in a cultural history of science opens up informative and refreshing perspectives: The period of romantic and idealistic philosophy, usually derided as obscure and dark, appears here as a time of intellectual fecundity, enabling conflicting interests and ideas to harmonize and create a milieu of conceptual freedom. Experimental physiology, although contributing to the success of localizationism in the 1870s, was not an unequivocal force of progressive change but could also be employed for the protection of the Cartesian framework, as done especially by Georges Cuvier in France. In Germany, under the pressures of institutionalizing their new biophysical form of experimental physiology, pioneers of a materialistic worldview—such as Du Bois-Reymond, Helmholtz, and Brucke—refrained from making statements about the mind’s link to the brain that were beyond experimental validation. During the first half of the nineteenth century, physiology succeeded anatomy as the leading medical science, enforcing stringent standards of experimentalism inapplicable to the brain and thereby impeding the “cerebralization” of physiology. Using quantitative measurements from the brain, anthropology and comparative anatomy, embryology and developmental biology began to address questions of racial, sexual, and interspecies differences—finally blending these strains of research into forms of knowledge that would have the most serious consequences in the twentieth century.

This fascinating and convincing account of the appropriation of the brain as a turning point in the history of the human sciences makes the reader hungry for more details. Although we do learn about the special needs of psychiatrists, and later of some clinicians, what were the analogous sociopolitical constraints on neuroanatomists pursuing their scientific activities, especially in the first decades of the nineteenth century? We are told about the defeat of Prussia at Jena, and about religious prejudices, but in what specific way do political circumstances or religious beliefs articulate with the history of the sciences of the brain? What about philosophy? Hagner sides with the neurosciences in their attack on philosophy, rather than revealing the causes and factors contributing to its decline. He rightly celebrates Gall as Kant’s best pupil in avoiding any metaphysical...