The son of Aelius Nicon, a wealthy architect with scholarly interests, Galen received a comprehensive education that prepared him for a successful career as a physician and philosopher. Born in Pergamon (present-day Bergama, Turkey), Galen travelled extensively, exposing himself to a wide variety of medical theories and discoveries before settling in Rome, where he served prominent members of Roman society and eventually was given the position of personal physician to several emperors.
Galen saw himself as both a physician and a philosopher, as he wrote in his treatise entitled That the Best Physician Is Also a Philosopher. Galen was very interested in the debate between the rationalist and empiricist medical sects, and his use of direct observation, dissection and vivisection represents a complex middle ground between the extremes of those two viewpoints. Many of his works have been preserved and/or translated from the original Greek, although many were destroyed and some credited to him are believed to be spurious. Although there is some debate over the date of his death, he was no younger than seventy when he died.
In medieval Europe, Galen's writings on anatomy became the mainstay of the medieval physician's university curriculum, but because of the collapse of the Roman Empire in the West they suffered greatly from stasis and intellectual stagnation. However, in the Eastern Roman Empire and the Abbasid Caliphate they continued to be studied and followed. Some of Galen's ideas were incorrect, as he did not dissect a human body. Greek and Roman taboos had meant that dissection was usually banned in ancient times, but in Middle Ages it changed: medical teachers and students at Bologna began to open human bodies, and Mondino de Luzzi (ca. 1275–1326) produced the ﬁrst known anatomy textbook based on human dissection.
Galen's original Greek texts gained renewed prominence during the early modern period. In the 1530s, Belgian anatomist and physician Andreas Vesalius took on a project to translate many of Galen's Greek texts into Latin. Vesalius's most famous work, De humani corporis fabrica, was greatly influenced by Galenic writing and form.
Galen's name Γαληνός, Galēnos comes from the adjective "γαληνός", "calm".
Galen describes his early life in On the affections of the mind. He was born in September AD 129. His father, Aelius Nicon, was a wealthy patrician, an architect and builder, with eclectic interests including philosophy, mathematics, logic, astronomy, agriculture and literature. Galen describes his father as a "highly amiable, just, good and benevolent man". At that time Pergamon (modern-day Bergama, Turkey) was a major cultural and intellectual centre, noted for its library, second only to that in Alexandria,
and attracted both Stoic and Platonic philosophers, to whom Galen was exposed at age 14. His studies also took in each of the principal philosophical systems of the time, including Aristotelian and Epicurean. His father had planned a traditional career for Galen in philosophy or politics and took care to expose him to literary and philosophical influences. However, Galen states that in around AD 145 his father had a dream in which the god Asclepius (Aesculapius) appeared and commanded Nicon to send his son to study medicine. Again, no expense was spared, and following his earlier liberal education, at 16 he began studies at the prestigious local sanctuary or Asclepieum dedicated to Asclepius, god of medicine, as a θεραπευτής (therapeutes, or attendant) for four years. There he came under the influence of men like Aeschrion of Pergamon, Stratonicus and Satyrus. Asclepiea functioned as spas or sanitoria to which the sick would come to seek the ministrations of the priesthood. Romans frequented the temple at Pergamon in search of medical relief from illness and disease. It was also the haunt of notable people such as Claudius Charax the historian, Aelius Aristides the orator, Polemo the sophist, and Cuspius Rufinus the Consul.
Galen's father died in 148, leaving Galen independently wealthy at the age of 19. He then followed the advice he found in Hippocrates' teaching and travelled and studied widely including such destinations as Smyrna (now Izmir), Corinth, Crete, Cilicia (now Çukurova), Cyprus, and finally the great medical school of Alexandria, exposing himself to the various schools of thought in medicine. In 157, aged 28, he returned to Pergamon as physician to the gladiators of the High Priest of Asia, one of the most influential and wealthy men in Asia. Galen claims that the High Priest chose him over other physicians after he eviscerated an ape and challenged other physicians to repair the damage. When they refused, Galen performed the surgery himself and in so doing won the favor of the High Priest of Asia. Over his four years there, he learned the importance of diet, fitness, hygiene and preventive measures, as well as living anatomy, and the treatment of fractures and severe trauma, referring to their wounds as "windows into the body". Only five deaths among the gladiators occurred while he held the post, compared to sixty in his predecessor's time, a result that is in general ascribed to the attention he paid to their wounds. At the same time he pursued studies in theoretical medicine and philosophy.