Along with Hippocrates, Galen was the most celebrated physician of antiquity. Of all ancient physicians, he was also the one who exerted the most enduring influence not only on Western medical thought and practice but also on Western culture and philosophy in general. In spite of their early medieval oblivion, mostly due to linguistic barriers, in the eleventh century Galen’s works began to circulate again in Europe mainly through Arabic mediation. As soon as Latin translations were made available by Italian and Spanish scholars, Galen entered the canon of natural philosophy, medicine, and anatomy. This medieval revival of the Galenic tradition continued throughout the late-medieval period and reached its apex during the Renaissance with the 1525 Aldine edition of Galen’s Greek texts, which set a benchmark for all subsequent editions and translations.Footnote 1 Soon afterwards, Galen’s medical supremacy began its slow but constant decline under the impact of new anatomical and physiological discoveries and the attacks by recently established rival schools of medicine like Paracelsian iatrochemistry and post-Cartesian iatromechanism. The prestige of erudite medical education was partially overshadowed by increasing claims to more empirically based and practically oriented medicine. Staunchly Galenic institutions like the London College of Physicians and the University of Paris had to confront, on the one hand, the emergence of professional guilds and corporations, and, on the other hand, the growing authority of independent scientific organisations like the Royal Society and the Académie des Sciences. However, notwithstanding a considerable loss of ground, early modern medical Galenism proved capable of surviving the challenges of the Scientific Revolution and managed to last throughout the sixteenth, seventeenth, and even eighteenth centuries.Footnote 2

The persistence of remnants of Galenism in spite of the gradual obsolescence of its overall theoretical framework is currently a lively topic in the history of medicine. Galen’s influence, however, was not limited to the medical field. Although his theories and practices certainly represented a mandatory reference point for early modern anatomy, physiology, and therapeutics, their revival easily crossed disciplinary boundaries. Galen’s discussion of so-called critical days in De diebus decretoriis, for instance, was paramount to the debates on astrology and its relevance to medicine.Footnote 3 Even more remarkable was his impact on philosophy, as he undeniably contributed to orienting the reception and interpretation of Aristotle’s natural philosophy and psychology up to the modern age. In particular, his De usu partium became a reference work for any approach to the Aristotelian biological treatises,Footnote 4 and his Quod animi mores played a role in revitalizing the study of the human soul.Footnote 5

So far, most studies on Galen’s early modern legacy have been selective in the choice of both topics and time span, as they have mainly focused, on the one hand, on the specifically medical side of Galenism and, on the other hand, on the post-medieval period and the Renaissance. Special attention has frequently been paid to Galen’s presence in the medicine and physiology of the sixteenth century. The reasons for this emphasis are perfectly understandable, since the sixteenth-century editions of his works had the indisputable effect of reviving the interest in this author in both the medical and the philosophical community. However, this privileged focus on the sixteenth century may easily result in overlooking the long-term effect of Galen’s rediscovery, which in fact did not cease to exert its powerful influence on both medicine and philosophy throughout the seventeenth and eighteenth centuries. On the other hand, the purely medical perspective adopted by several studies has left the philosophical import of early modern Galenism largely unexplored. In the seventeenth century, Galen’s theories appear to have been mentioned, endorsed, discussed or even opposed in the works of first-rank scientists and philosophers such as Bacon, Descartes, Boyle, Cudworth, Locke, and Leibniz – just to name the best known. In this perspective, the early modern reception of Galen shows with perfect clarity that scientific discoveries and philosophical ideas do not necessarily develop together or reflect the same attitude towards ancient authorities. Even after becoming largely obsolete as a scientific and medical system, Galenism was still able to inspire philosophical debates and inform philosophical theories.

Galen, who considered himself a philosopher and maintained that the best doctor is also a philosopher, did not hesitate to combine the physician’s approach with the philosopher’s one as two distinct, albeit related, perspectives in one of his most successful and most philosophical works, the treatise De usu partium. In its final book, the famous Epode, Galen points out that the intended audience of De usu partium is neither necessarily nor primarily composed of physicians; rather, the treatise is intended for philosophers: ‘Hence such a work is serviceable not only for the physician, but much more so for the philosopher who is eager to gain an understanding [ἐπιστήμην] of the whole of Nature’ (De usu partium, Book XVII, Chap. 1: Galen 1907–1909, Vol. 2, 447–448: Galen 1968, 731). Of course, the physician benefits from knowledge about the inner workings of the body insofar as this knowledge has important diagnostic uses, but this medical advantage appears explicitly subordinate to the purely theoretical advantage that consists in knowing, first, that there is such a thing as usefulness – against those who deny it – and, second, what it means for a part to be useful (De usu partium, Book XVII, Chap. 2: Galen 1907–1909, Vol. 2, 449–450). The philosophical understanding of usefulness is itself intrinsically useful, as it paves the way to recognizing the marks of a wise demiurge in the structures of all animals: ‘Then a work on the usefulness of the parts … will be reckoned truly to be the source of a perfect theology, which is a thing far greater and far nobler than all of medicine’ (De usu partium, Book XVII, Chap. 1: Galen 1907–1909, Vol. 2, 447: Galen 1968, 731). Galen’s theology clearly pivots on teleology.

In the early seventeenth century, the distinction between a primary, ‘philosophical or rather theological’ usefulness of the work, and a secondary, medical one was established as a key exegetical principle at the very beginning of Caspar Hofmann’s influential commentary on De usu partium (Hofmann 1625, Prolegomena, 2). The title page of the volume already warns the reader that the work is ‘intended not only for physicians but also for philosophers as well as philologists’ (Hofmann 1625). By interpreting the relation between demiurge and nature as a relation between Creator and creatures, Hofmann managed to present Galen’s teleological program as aimed at the same epistemic goal that is adumbrated in St Paul’s Epistle to the Romans, namely ascending from the contemplation of creatures to the recognition of the Creator (Hofmann 1625, 2). Interpreted in this way, the Epode provided even stronger support for the theologically-oriented and Christianized reading of Aristotle’s physics. In spite of some prominent metadisciplinary differences between ancient and modern conceptions of teleological investigation,Footnote 6 the finalistic account of organic structures and functions offered by De usu partium became a decisive source not only for the seventeenth-century development of physico-theology but also for the eighteenth-century rise of teleology as an autonomous philosophical discipline.

However, in spite of this strategic alliance in the name of finalism, Christian thought was never entirely and unconditionally favorable to Galen’s reception. The most serious issues arose from the ambivalence that seemed to pervade Galen’s philosophical doctrines when these were considered from the point of view of the Christian faith. As Temkin puts it, from its inception Galenism revealed ‘a double face of materialism and of worship of divine wisdom and providence’ (Temkin 1973, 186). Galen’s concept of nature and his problematic identification of nature and God fuelled the debates on modern naturalism and its alleged atheistic implications. Further theological concerns came from Galen’s professed agnosticism concerning the ultimate nature of the soul and his suggestion that the soul could be a mixture, which were (not completely without reason) accused of paving the way to materialism.

However important and complex, the theological issues that gave rise to attempts either to reconcile Galenism and Christian thought or to set them in contrast are still only one side of Galen’s reception in early modern Europe. Far from surviving as a single and unequivocally identifiable school of thought, post-Renaissance Galenism spread its influence across different or even competing schools. The opposition between the two great trends in early modern philosophy of nature, mechanism and vitalism, was also based on their acceptance and rejection of different aspects of the Galenic life sciences. Mechanists themselves were internally split between those who opposed Galen because of his commitment to the Aristotelian ontology of nature, populated with faculties, qualities, temperaments, etc., and those who tried to recast key elements of Galenic physiology, like the notions of temperaments or animal spirits, in mechanistic terms (see Favaretti Camposampiero 2020). Furthermore, Galen’s efforts to characterize the fundamental concepts of health and disease by means of a distinction between natural and preternatural states inspired early attempts to build a philosophy of medicine in the sense of a philosophical analysis of medical concepts.

When investigating the relation between early modern medicine and philosophy as well as the relation between their respective professional or academic representatives, we should also consider the educational system and especially the organization of academic instruction (see Manning 2021). The typical student in medicine (one of the three traditional superior faculties, along with law and theology) previously earned a degree from the lower faculty of arts, which included the study of philosophy. Medical training was conceived ‘as an outgrowth of preparatory philosophical studies, specifically in natural philosophy’ (Levitin 2015, 233). As a consequence, the professor of theoretical medicine and the professor of philosophy were not so entirely alien to each other as we might imagine them to be. On the contrary, both figures shared a common philosophical background. Moreover, this common background was in fact not limited to philosophy in our strict sense, as natural philosophy (especially in its Aristotelian versions) also included elements of animal and human physiology. If the physician did not lack philosophical training, neither did the philosopher ignore the fundamentals of medical knowledge. Thus, the fact that several early modern philosophers were interested or even actively involved in medical research should not be viewed as the fortunate consequence of their personal, eccentric curiosity, but rather as a characteristic result of the early modern organization of knowledge.

In light of these considerations, the present collection of studies aims to broaden our understanding of Galen’s reception in early modern philosophy of nature, rational theology, teleology, physiology, botany, medicine, and philosophy of medicine by investigating Galen’s presence from the sixteenth to the eighteenth century. In particular, our aim here is to provide a picture of the fruitful and diversified interactions between medical and philosophical Galenisms that took place in several areas of early modern thought. Although the authors investigated in the following chapters are by no means the only ones of interest to the history of early modern Galenism, our selection shows the varied character of this phenomenon, in that it explores a plurality of ways in which early modern philosophers, coming from very different cultural contexts and philosophical backgrounds, were able to react to the suggestions and challenges posed by Galen’s doctrines. It is our hope that this seminal work may stimulate future research.

By exploring some episodes in the reception of the Galenic doctrine of the natural faculties, Guido Giglioni shows how challenging and thought-provoking Galen’s very concept of natural faculty proved to be in the eyes of early modern philosophers and scientists, insofar as it motivated the ascription of an unconscious yet purposeful agency to nature. A distinctive trait of early modern Galenism consisted in considering life and vital processes like nutrition and growth to originate from such active powers of the body itself, thereby providing a long-running alternative to the mechanistic account of matter and living bodies.

Galen’s relevance to the history of causality is not limited to his endorsement of finalism but also concerns the investigation and classification of efficient causes. Whereas anatomists and physiologists were interested in knowing the uses of the parts of the body, a rational (i.e., not purely empirical) approach to pathology and therapeutics required physicians to be able to discern, recognize, and treat the causes of diseases. Being a Galenist also meant championing an ideal of medicine as based on the knowledge of causes. Craig Martin’s contribution to the present volume shows how seriously early modern scholars could take Galen’s effort to distinguish and classify different types of efficient causation and how doggedly they strove to refine those ancient causal categories. Far from being a merely theoretical exercise, through its doctrinal sophistication Giambattista Da Monte’s discussion of Galenic causes in medicine pursued the practical goal of enhancing the rational physician’s diagnostic and healing skills.

No less methodologically inspiring was Galen’s interest in the vegetable world, which led him to emphasize the structural and functional similarities between plants and animals more than his predecessors had done. After providing evidence that Galen construed the traditional plant-animal analogy as a genuine identity of forms and functions, Fabrizio Baldassarri argues that this approach prepared the ground for the early modern adoption of the vegetable body as a model for investigating the vital operations of all living bodies. In the first half of the seventeenth century, first-rank figures in medicine and botany like André du Laurens, Fabricius ab Aquapendente, Adriaan van den Spiegel, Jean Riolan the Younger, and William Harvey were all in various ways engaged in testing, developing, or appropriating Galen’s ‘continuistic’ account of plants and animals.

On the other hand, Claire Crignon shows that Galen’s strictly methodological work and his stance on the long-standing debates among medical sects on the correct method of healing attracted John Locke’s attention, influencing both his eclectic medical epistemology and his tolerant approach to disagreement. In Crignon’s reading, Locke’s early criticism of Galen’s rationalistic ambition to explain diseases from their remote causes turns out to be consistent with his later rehabilitation of the ancient, Galenic-inspired tradition of preventive medicine and dietetics. The importance Locke ascribed to health regimens in his educational writings reveals how much he considered medicine to be an integral part of philosophy.

The reception of Galen in seventeenth- and eighteenth-century British rational theology was predominantly philosophical in character. Brunello Lotti analyzes the different ways in which Christian thinkers from Thomas Browne to William Paley sought to accommodate the two protagonists of Galenic theology, namely the demiurge and nature. Galen’s emphasis on nature’s autonomy and intelligence was perceived as especially problematic in this respect. Thus, while in the case of the demiurge there was a common tendency to identify him with the Christian God, in the case of nature the various attempts at Christianization did not adopt a uniform strategy. Whereas Galen’s finalism provided weapons in the fight against impious forms of mechanism and atomism, Galen’s naturalism seemed to pave the way to atheism. However, as Lotti argues, Christian apologists privileged Galen’s De usu partium over his strictly medical works also because of its focus on the healthy body, which dispensed them from addressing the theologically embarrassing issue of disease.

The existence and early modern consolidation of a tight link between Galenism and finalism are confirmed by the fact that, in the seventeenth century, radical anti-finalism expressed itself as anti-Galenism. Emanuela Scribano identifies Cartesian mechanism as the real alternative to Galenic finalism. Two prominent opponents of Galenic finalism, Guillaume Lamy and Jean-Baptiste Verduc, drew on Cartesian arguments and doctrines in order to reject both Galen’s identification of functions with ends and his fundamental assumption that the organic body must be the work of intelligence. In both Lamy’s and Verduc’s account of physiological functions, the action of such an intelligent principle organizing the body either from without or from within was replaced with the functioning of pure mechanism.

Notwithstanding its centrality in the debate on final causes, not every aspect of Galen’s finalism was perfectly consonant with modern tenets, and not every modern advocate of the existence of ends and purposes in nature was willing to simply follow Galen in his account of the usefulness of the parts of the human body. Raphaële Andrault points out the profound differences between Leibniz’s teleology and Galen’s, arguing that the label of Panglossianism that has been frequently used to describe the former might in fact better apply to the latter. In Leibniz’s case, the identification of Galen’s demiurge with God shows its intrinsic flaws. The infinite power and wisdom that characterize Leibniz’s God and His choice among infinite possible worlds full of infinite possible creatures give a different meaning to the optimistic claim that Leibniz apparently shares with Galen, namely that the actual world is the best possible one.

In spite of these divergences, however, the stimulus given by Leibniz to the rehabilitation of final causes in natural philosophy contributed to the revival of Galenism in eighteenth-century German philosophy. As documented by Matteo Favaretti Camposampiero, Christian Wolff’s extensive treatment of natural teleology expressly draws on Galen’s analysis of physiological functions in De usu partium. Furthermore, Wolff’s attempt to provide a philosophical foundation for medicine by analyzing its basic concepts of health, disease, etc., features several references to Galen’s works on diseases and symptoms. As with Locke (see Crignon’s chapter in this volume), Wolff’s knowledge of Galen was largely mediated by Daniel Sennert. The role played by indirect sources in the transmission of Galenic doctrines suggests that the actual circulation of Galenism in early modern philosophy was to some extent independent of the history of Galen’s editions.

The less visible but no less important presence of Galenic doctrines in the cultural context of materialism shows, first, that early modern thinkers practiced at least one form of philosophical Galenism alternative to its finalistic, theologically-oriented version; second, that the reservations and fears expressed by religious apologists concerning the spread of Galen’s teachings among materialists and atheists were not entirely unjustified. Charles T. Wolfe pinpoints two major legacies that modern materialism inherited from Galenism: on the one hand, the grounds for the stereotypical association between atheistic tendencies and the medical profession; on the other hand, the non-spiritualistic characterization of the soul as a mixture, which undermines any argument from simplicity and makes the soul eo ipso liable to disease and death.

Notwithstanding the mainstream discredit of Galenism as a conservative tradition, not all Enlightenment philosophers were blind to the methodological similarities between Galen’s approach to knowledge and their own epistemic project. Tinca Prunea-Bretonnet’s reading of Kurt Sprengel’s 1795 work shows that, in the late eighteenth century, it was even possible to defend Galen as a champion of free thought and a model of sound, consistent, and methodologically robust eclecticism. Sprengel’s assumption that Galen’s doctrines constitute a philosophical system confirms the leitmotiv of the present volume. Once again, what captured the early modern eye was the possibility to draw philosophical inspiration from Galen in order to address urgent philosophical issues.