Galen (Claudius Galenus) was a physician, anatomist, and philosopher who lived in the 2nd century AD, born in Pergamon (modern-day Bergama). Active during the Roman Empire, he became one of the most influential figures in ancient medicine through his extensive writings on anatomy, physiology, clinical medicine, and treatment methods. Galen’s works decisively shaped medical teaching and practice until the late Middle Ages and early modern period; his name continued to be associated with various anatomical structures and concepts, particularly in anatomical literature.

Name and Epithets

In ancient sources, Galen is referred to in various forms depending on language and tradition. In Greek texts, his name appears as Γαληνός (Galenos), while in Latin sources it is rendered as Claudius Galenus. Some late Roman and Byzantine texts refer to him as Claudius Clarissimus Galenus.

In ancient and medieval literature, Galen is most commonly known as “Galen of Pergamum” (Galenos ho Pergamenos). This designation identifies his place of birth and distinguishes him from other individuals bearing the same name. In In the Islamic world and Arabic medical literature, Galen is generally known as “Câlînûs,” and his works were transmitted under this name.^【1】

Galen’s standing in medicine was regarded by his contemporaries as that of a supreme authority. Indeed, the Roman Emperor Marcus Aurelius described Galen as “the foremost of physicians and also a philosopher.”^【2】 Galen’s name is primarily used in its Greek and Latin forms, often accompanied by references to his place of origin.

Birth and Family

Galen was born around 129 AD in Pergamon, located in Asia Minor (modern-day Bergama, Türkiye). During the Roman Empire, Pergamon was a major cultural and intellectual center, particularly renowned for its Asklepieion, which made it a leading hub for medical education and healing practices. This environment provided a favorable foundation for Galen’s early intellectual and professional development.

Galen’s father, Aelius Nicon, was a wealthy architect and an intellectual with interests in mathematics, astronomy, philosophy, and literature. Nicon closely guided his son’s education, ensuring that Galen received comprehensive training in mathematics, logic, grammar, and philosophy from an early age.

According to ancient accounts, Galen’s decision to pursue medicine was linked to a dream experienced by Aelius Nicon. In the dream, Asclepius appeared to Nicon and instructed him that his son should study medicine. This vision led to a change in the originally planned philosophical or political education for Galen and resulted in his enrollment in medical studies at the Asklepieion in Pergamon.^【3】 After his father’s death around 149–150 AD, Galen became financially independent and gained the opportunity to continue his education at various centers.

Educational Travels and Scientific Formation

Galen’s medical and intellectual formation was shaped during extended educational journeys undertaken after his initial training in Pergamon. Following his father’s death and his newfound financial independence, Galen traveled to the leading scientific and medical centers of his time to deepen his knowledge. These journeys determined not only his medical knowledge but also his methodological and philosophical approach.

Galen spent time in İzmir, Corinth, and especially Alexandria, where he encountered diverse medicine traditions and teaching methods. His work with physicians in Smyrna and Corinth who held rationalist and empiricist views helped him develop a pluralistic attitude, evaluating different theoretical approaches without allegiance to a single medical school. Alexandria was one of the most important centers of the ancient world for anatomy and medical research. There, Galen emphasized the importance of anatomical instruction and highlighted the possibility of direct observation of the human skeleton.

Although it remains uncertain whether Galen directly performed human dissections in Alexandria, it is clear that he conducted intensive comparative anatomical studies. His dissections of primates and pigs formed the foundation of empirical knowledge in anatomy and physiology. The detailed anatomical descriptions found in his later works are directly linked to the experiences gained during this period.

Galen’s educational travels were not limited to medicine; they also encompassed philosophy, logic, and natural science. His exposure to Platonic, Aristotelian, Stoic, and Epicurean traditions provided the groundwork for an approach that integrated observation with theoretical explanation. The scientific formation developed during this period became the foundation of the medical understanding he later adopted and systematically applied in his writings.

Pergamon Period and Gladiatorial Medicine

After his educational travels, Galen returned to his native city of Pergamon around 157 AD and took up a position as a physician at the gladiator school. This role proved decisive in his professional development. Gladiatorial medicine required the treatment of severe traumas and recurrent injuries, providing Galen with direct opportunities to observe the living human body.

During this period, Galen gained extensive clinical experience in bones, joints, and muscles. The treatment of serious traumas such as chest and abdominal wounds, fractures, dislocations, and soft tissue injuries refined his surgical skills. At the same time, his ability to observe the healing processes of wounds enabled him to make empirical inferences about the relationship between anatomy and physiology.

Movement to Rome and Professional Ascendancy

Around 162 AD, Galen left Pergamon and moved to Rome. At that time, Rome was a center where medicine was intensely practiced but also marked by fierce professional competition and marked differences in quality. Galen quickly attracted attention through his lectures based on anatomy, public demonstrations, and clinical practices.

During his time in Rome, Galen demonstrated the functions of organs through experiments on live animals, a method that highlighted his experimental approach. These works impressed both his colleagues and elite circles, strengthening Galen’s medical authority.

However, his rapid rise also led to professional conflicts with certain physicians. These disputes resulted in Galen’s temporary departure from Rome around 166 AD. This separation was not permanent; shortly thereafter, Galen was recalled to Rome by imperial authority.

Between 168 and 169 AD, Galen was appointed as a physician to the army by Emperors Marcus Aurelius and Lucius Verus. He later returned to Rome, where he served as personal physician to Marcus Aurelius, then to Commodus, and subsequently to Septimius Severus. This position granted Galen both political protection and the opportunity to continue his scientific work. His role at court enabled him to observe a wide range of patient profiles and produce a large number of writings.

Scientific Method and Medical Approach

Galen’s scientific method is defined by his effort to combine empirical data derived from observation with theoretical explanations. He argued that medical knowledge could not rely solely on individual experiences but required their integration into general principles. In this way, Galen sought to strike a balance between pure empiricism and rationalist traditions that prioritized causal explanation.

Galen maintained that medicine was not merely an empirical field but required rational grounding through reason. While adhering to Hippocratic medicine, he did not deny the importance of experience; he viewed medicine as a theory continuously refined through observation and practice. In this approach, anatomical and physiological studies held a central role in the formation of medical knowledge.^【4】

Anatomical data obtained through dissection played a central role in Galen’s inferences about physiological processes. He believed that the structure of organs was inherently suited to their functions, a principle that formed the basis of his medical explanations. Within this framework, Galen adopted the principle that nature does nothing in vain and sought to explain anatomical variations through functional causes.

The concept of balance was central to his medical approach. Health was defined as a harmonious balance among the body’s components, while disease was understood as a disruption of this balance. Treatment was regarded as a rational and measured intervention aimed at restoring this equilibrium.

Philosophical Background and the Relationship Between Medicine and Philosophy

Galen’s intellectual formation was grounded in the belief that medicine and philosophy could not be separated. Although he did not explicitly identify himself with any single philosophical school, his writings extensively engaged with philosophical concepts, methods, and debates. While critically engaging with contemporary professional philosophers, Galen regarded philosophy as essential for grounding medical knowledge.

His philosophical background is particularly linked to Platonic and Aristotelian traditions. From Plato, he adopted the model of the soul’s divisions and ethics psychology; from Aristotle, he embraced methodological principles concerning logic, causality, and the study of nature. Nevertheless, Galen evaluated these thinkers not as absolute authorities but as sources to be consulted only insofar as they aligned with medical observations.

The relationship between medicine and philosophy in Galen’s thought also carried an ethical dimension. He argued that a physician must possess not only technical knowledge but also the capacity for sound judgment and moral responsibility. Thus, in his view, medicine was not merely a practice aimed at treating bodily illnesses but a field of knowledge seeking a holistic understanding of human nature.

Anatomical and Physiological Studies

Galen’s work in anatomy and physiology occupies a central place in the medical heritage. These studies aimed to explain the relationship between organ structure and function, based on the understanding that anatomy is a necessary foundation for comprehending physiological processes. Galen did not regard anatomy merely as a descriptive discipline but as an indispensable tool for causal explanation.

In an era when human cadaver dissection was limited, Galen relied heavily on animal dissections to acquire anatomical knowledge. His comparative studies on primates and pigs enabled him to make inferences about the human body. Although this method led to some anatomical errors, it facilitated the development of detailed descriptions of the nervous system, muscles, blood vessels, and internal organs.

Galen demonstrated that nerves originate in the brain and that the brain is the center of sensation and voluntary movement. He clearly distinguished the vascular and nervous systems, rejecting the view that arteries carried only air; instead, he proposed that blood and pneuma circulated together. His functional distinction between the heart, liver, and brain was based on the idea that different vital processes in the body were governed by distinct centers.

In physiology, Galen adopted a teleological approach, arguing that organs are organized toward specific purposes. This perspective is evident in his explanations, which link structural features to their functions. The principle that nature creates nothing useless or purposeless formed the foundational assumption of Galen’s anatomical and physiological studies.

The Galenic Medical System

Galenic medical system integrates Galen’s views on anatomy, physiology, pathology, and treatment into a unified theoretical framework. This system emerged from the combined use of empirical clinical experience and conceptual tools drawn from natural philosophy. Galen positioned medicine not merely as a practical discipline but as a rational science aiming to explain causes.

The central concept of this system is balance. Health was defined as a harmonious balance among the body’s components, while disease was understood as a disruption of this balance. This approach explained bodily conditions through combinations of opposing qualities—hot-cold and dry-moist—in specific proportions.

Humoral theory is one of its central elements. The four humors—blood, phlegm, yellow bile, and black bile—were linked to bodily and psychological processes. The quantitative and qualitative balance of these humors was regarded as a primary determinant of an individual’s health. Galen interpreted diseases not as isolated organ disorders but as systemic imbalances affecting the entire body.

The therapeutic approach was based on the principle of contraries. The treatment should counteract the quality responsible for the disease. This principle was systematically applied in dietary regimens, drug use, and other therapeutic interventions. While acknowledging general rules, Galen emphasized that each patient’s bodily constitution and medical history must be considered; he regarded the adaptation of theoretical knowledge to clinical circumstances as a fundamental responsibility of medicine.

Galen in the Middle Ages and the Islamic World

Galen’s establishment as a fundamental authority in medieval medicine was decisively shaped by the activities of examination, abridgment, and commentary in the Islamic world. It is known that before the rise of Islam, scholars of the Alexandrian school had extensively studied Galen’s works, and this corpus became known in the Islamic world as Cevâmiʿu’l-İskenderâniyyîn and in the West as Summaria Alexandrinorum.^【5】 This tradition served as an intermediary corpus that facilitated the circulation of Galen’s texts and supported their standardization in medical education.

Translation activities played a central role in strengthening Galen’s authority in the Islamic world. Hunayn ibn Ishaq’s Risâle, which records the Galenic works translated into Arabic, is among the primary sources of this process. Hunayn had seen the original version of Galen’s Pinax, a catalog of his medical and philosophical works, and translated it into Syriac and Arabic, adding a third list of works not included in the original catalog. It is known that Hunayn and his collaborators translated 129 Galenic works from Syriac manuscripts into Arabic. This effort ensured the systematic classification and continued circulation of Galen’s corpus within Islamic scholarly circles.

Galen’s influence in the Islamic world was also evident at the level of medical theory and practice. While maintaining fidelity to Hippocratic medicine, he adopted an approach that did not reject experience; he viewed medicine as a theory continuously developed through observation and practice. Muslim physicians regarded Galen not merely as a transmitter of authority but as a source from which new knowledge in pharmacology, anatomy, and treatment could be derived. It is known that Galen’s anatomical observations remained a reference for anatomists of the 16th and 17th centuries, and that his insight into the presence of blood rather than air in vessels and his partial understanding of the pulmonary circulation attracted attention.

Nevertheless, Galen was not accepted as an absolute and unquestioned authority in the Islamic world. The Kitâbü’ş-Şükûk ʿalâ Câlînûs by Abu Bakr al-Razi, known as “Galen of the Islamic world,” is among the earliest critiques directed at Galen’s medical and philosophical views. These critiques claimed that certain clinical observations did not align with Galen’s corpus. Medical circles seeking to preserve Galen’s authority responded with refutations; the most famous example is Ali ibn Ridwan’s refutation. It is also known that a student of Ibn Sina and Ibn Zuhr wrote refutations with the same title.

Impact in the Renaissance and Beyond

With the Renaissance, Galen’s authority in medicine was reevaluated; reading ancient texts in their original languages enabled direct examination of his works in Greek. This process facilitated both a more accurate understanding of Galen’s views and their critical assessment.

In particular, human cadaver dissections conducted during the Renaissance revealed that some of Galen’s explanations, based on animal anatomy, were incorrect. Renaissance anatomists, while maintaining respect for Galen, developed new anatomical descriptions grounded in direct observation. These critiques were directed not at Galen’s method per se but at the consequences of limited observational conditions.

Nevertheless, Galen’s scientific approach—integrating observation with reasoning—continued to influence the development of medicine after the Renaissance. His integration of medicine with philosophical foundations contributed to medicine’s emergence as an intellectual discipline in the early modern period. The Galenic system was adapted and transformed in light of new scientific discoveries and served as a critical reference point in the development of modern science.

Place and Significance in the History of Science

Galen is regarded as one of the most important figures in whom ancient medicine achieved theoretical coherence. His significance in the history of science is not limited to specific anatomical or physiological views; his decisive contribution lies in his effort to transform medical knowledge into a systematic, rational, and justified field. His approach of integrating observation with theoretical explanation helped elevate medicine beyond a mere practical craft.

Building on the Hippocrates tradition, Galen expanded this legacy with philosophical concepts, logical inferences, and physiological explanations. His functional analysis of organs, causal explanations based on cause-effect relationships, and holistic model of the body rendered ancient medical knowledge more consistent and teachable than in previous eras.

Galen’s influence endured for centuries in the Byzantine, Islamic, and Latin medieval worlds; his works formed the theoretical backbone of medical education. Although some of his views were abandoned during the Renaissance and early modern period, his writings retained their importance as a necessary reference point in the development of modern science. In this context, Galen is not merely an authority to be criticized but a central figure who provided a lasting model for how knowledge is constructed.

Death

Information regarding Galen’s death is limited. Ancient biographical accounts generally accept that he died in the late 2nd century or early 3rd century AD. Traditional chronology places his death around 200 AD; this view gained widespread acceptance through Byzantine sources and medieval compilations.

However, modern research indicates that this dating is not certain. Studies by modern historians such as Vivian Nutton suggest that Galen may have lived longer. Some indirect information in late antique and early medieval Arabic and Byzantine sources implies that Galen may have lived until the 210s AD. Accordingly, it is plausible that his death coincided with the final years of Emperor Septimius Severus or the reign of his son Caracalla.

No clear or reliable information exists regarding the place or cause of Galen’s death. No account links his death to a sudden illness or specific event. This situation is often associated with the fact that the final years of his life were largely devoted to writing and intellectual production. Indeed, in his later works, Galen reflects on aging, material losses, and the destructive passage of time; however, there is no direct autobiographical record of his death.

Works

Galen is regarded as one of the most prolific authors of antiquity. According to his own statements and ancient catalogs, he wrote over 300 works; although a significant portion has not survived, approximately 120 works have been preserved in whole or in part through Greek, Latin, Arabic, and Syriac transmissions.^【6】 The total volume of surviving Galenic texts exceeds four million words.

Galen’s works cover a broad range of subjects, including medicine, anatomy, physiology, pharmacology, clinical practice, methodology, logic, ethics, and philosophy. A significant portion of his writings are didactic, while others contain polemical critiques directed at contemporary medical schools, particularly the Empiricists and Methodists.

Medical and Clinical Works

Galen’s most influential works relate to medical theory and clinical practice. In these texts, the causes, symptoms, diagnosis, and treatment of diseases are systematically addressed.

• De Methodo Medendi (On the Method of Healing): One of the most comprehensive works outlining Galen’s clinical approach, arguing that treatment must be based on the cause of the disease.
• De Sanitate Tuenda (On the Preservation of Health): Contains views on preventive medicine, diet, exercise, and lifestyle.
• De Locis Affectis (On Affected Parts): Addresses methods for determining the location of diseases in the body.
• Fî Ṣınâʿati’ṭ-ṭıb (On the Art of Medicine): Addresses both the theoretical and practical aspects of medicine as a unified whole.
• Fî Taḳdimeti’l-maʿrife: Contains evaluations on the acquisition and organization of medical knowledge.

Anatomical and Physiological Works

Galen’s anatomical works are largely based on animal dissections and shaped by a comparative anatomy perspective.

• De Usu Partium (On the Usefulness of the Parts of the Body): Presents a teleological understanding of anatomy, linking organ structure to function.
• De Anatomicis Administrationibus (On Anatomical Procedures): Contains descriptions of dissection techniques and anatomical observations.
• De Nervorum Dissectione: Provides detailed studies on the structure and distribution of nerves.
• De Motu Musculorum: Examines the anatomical and physiological foundations of muscle movement.
• Fî Menâfiʿi’l-aʿżâʾ: Presents a physiological approach linking organ functions to purposefulness in nature.

Pharmacology and Materia Medica

Galen wrote extremely detailed works on drugs and natural substances.

• De Simplicium Medicamentorum Temperamentis ac Facultatibus (On the Temperaments and Powers of Simple Drugs)
• De Compositione Medicamentorum (on drug formulations and compounds)

The approach developed in these works formed the basis of the pharmaceutical tradition later known as “galenic preparations.”

Philosophical and Methodological Works

Galen’s philosophical works aim to ground medicine, nature, and human understanding.

• Quod Optimus Medicus Sit Idem Philosophus: Addresses the relationship between medicine and philosophy.
• De Sectis: Compares the methods of ancient medical schools.
• De Demonstratione: A work on scientific proof, which has not survived.
• Fî Enne ḳuva’n-nefs tevâbiʿ li-mizâci’l-beden: Examines the relationship between mental faculties and the body’s temperament.
• Kitâbü’l-Aḫlâḳ: Addresses the relationship between human temperament and ethics.

Ethics and Theory of the Soul

• De Placitis Hippocratis et Platonis: Aims to reconcile Plato and Hippocrates on the structure of the soul and its bodily foundations.
• De Animi Affectibus and De Animi Peccatis: Contain ethical-psychological evaluations of passions, moral errors, and mental disorders.

Transmission of Texts and Influence

Galen’s works were preserved in the Byzantine world through Greek manuscripts and in the Islamic world through Arabic translations made in the 9th and 10th centuries. The translations by Hunayn ibn Ishaq and his circle established Galen’s central role in medieval Islamic medicine. During the Renaissance, his works were translated into Latin and became foundational textbooks in European universities.