Assess the importance of Galen in the history of medicine.


“With the exception of Aristotle, and the possible exception of Plato, there can be no more historically influential ancient author [than Galen] in matters scientific,” according to P.N Singer.[1] Over the course of his life, he wrote on medicine, logic, philosophy, philology and criticised existing literature.[2] Initially, Galen had been groomed for a philosophical life until his father pushed him towards the medical art; their family wealth secured him a varied and lengthy period of medical study.[3] In 157 AD, Galen became a physician at a gladiatorial school, giving him the best on-the-job training in orthopaedic surgery; in comparison to his predecessors he was successful – hardly losing a single patient.[4] This essay will examine both Galen’s achievements and mistakes in the Ancient medical world in order to determine how important he was in the history of medicine. I will be undertaking this from two perspectives: how Galen actively contributed to knowledge of the body and drugs, and his significance as a dogmatic historian of medicine. I will firstly present Galen’s approach to medicine and the attributes he prescribed to contemporary physicians. Secondly, I will evaluate how successful Galen’s anatomical revelations were, before discussing his contribution to pharmacology as an alternative to surgery. I will finish by discussing Galen’s criticism of his contemporaries and his defence of Hippocrates, before considering his own legacy; this will ultimately determine his significance in the history of medicine.

Main Text

Galen believed that in order to complete their learning, physicians must be studious, objective and, above all else, possess a desire for the truth.[5] This learning should not be confined to solely medical texts, but rather encompass other disciplines such as astrology.[6] Evidence of this can be seen in Galen’s development of the theory of the four fundamental elements, whereby the qualities of these relate to substances of the universe, in addition to the four humors.[7] It is this holistic approach that later convinced physicians in Islamic countries of his ability.[8] Although Galen does not dismiss the necessity of a theoretical understanding, “his [own] exhaustive reading must take second place to direct observation.”[9] Galen placed a heavy emphasis on acquiring knowledge through engaging with the physical world and its creatures; this will become evident when discussing his use of dissection to develop existing anatomical knowledge. In his eyes, “practice, and still more practice, was essential” to becoming the best physician.[10] Ultimately, this enabled him to “not only get things right, but explain how.”[11] To the best of his ability, Galen concluded what he understood based on observation, theory, and a knowledge of his predecessors.[12] Flemming would argue that perhaps “Galen’s claim to medical authority…is rooted in his…conformity, even identity, with the twin ideals he establishes: equipped by birth and education”, and could be reduced to “strident self-promotion”.[13] Certainly, these ideals match the qualities he saw in himself, and one must question who gave Galen the authority to set the standards of the medical profession. Galen believed that the study of medicine would enable him to complete the framework left by Hippocrates, and thought that learners should therefore follow his advice as an example of a Hippocratic physician.[14] Regardless of whether Galen was attempting to promote himself, the attributes he gives to physicians combined with his emphasis on practical experience provided a new approach to the study and practice of medicine.

Just as Galen took a holistic approach to the study of medicine, he aspired to connect his whole body of research to present an integrated, overall system, as opposed to several separate ones.[15] Galen advanced knowledge of the cardio-vascular and nervous systems, distinguishing arteries from veins and describing the motion of blood through the heart and body.[16] In addition, he had a clearer understanding than his predecessors, of the function of the brain and its relationship with nerves.[17] This knowledge was acquired through dissection, which to Galen was the “hallmark of the complete physician”.[18] One of the most spectacular displays of anatomy was Galen’s experiment with the nerves on the vocal chords, with the animal “suddenly becom[ing] silent after the nerves had been tied”; a performance that, according to Book 8 of AA, Chapter 4 (II 667-75) his spectators thought was “wonderful”.[19] Ultimately, Galen was aimed to teach and demonstrate through dissection; astonishment was also important in order to impress a prospective patient or rival of his capabilities.[20] To prove that his contemporaries and predecessors were incorrect, and that he was correct, he invited spectators to nominate parts of the body for dissection and discourse, letting “the excellence of his practice speak for him.”[21] It is clear from both this and his writings that Galen was not above causing his colleagues embarrassment.[22] For the most part, “dissection for the sake of acquisition of new knowledge was not considered” before Galen’s time, with methodists adopting beliefs without demonstration.[23] From conducting enquiry on the body, Galen was able to conclude on the nature and function of organs and from this created a systematised and structured explanatory system, which “only someone gifted and practiced in logic” could do.[24] Galen was faced with the criticism of empiricists, such as Celcus, who believed – particularly if the subject was dead – that the body was not under its normal conditions and therefore dissection could not provide a true understanding from which to conclude.[25] Despite this, I would argue that the practice of dissection was clearly essential to the enhancement of anatomical knowledge (thus allowing for the application more effective treatment). Arguably however, contemporary empiricists were right to criticise Galen’s dissection. The dissection of human bodies was forbidden at the time Galen was practicing as a physician; therefore, his only alternative was to use animals such as apes and pigs. This meant that his work contained inaccuracies due to the body differing from that of a human. For example, Galen believed that the left kidney was lower than right kidney, as this is true of an ape – chosen as it most resembles man.[26] These mistakes were not discovered until the universities of Oxford and Cambridge instructed anatomical teaching in the 1500s, and found that “not everything that Galen had said appeared to be confirmed by the evidence of observation.”[27] Whilst Galen cannot be wholly criticised, as his inaccuracies were due to restriction rather than incompetent dissection, his “only mistake”, according to historian of medicine William Bynum, was that he did not inform the reader where he got his knowledge from, despite being conscious of the problem of “extrapolating from animals to human beings.”[28] Had Galen said in his works that he had acquired his knowledge from the dissection of a monkey, his successors would not think that the human body had changed, but instead could have discovered the true anatomy of the human body sooner.[29] That said, he did provide much of the anatomical knowledge that William Harvey later based his theory of circulation upon, and Galen’s descriptions of many bones of the body are still considered acceptable today.[30]

In addition to influencing anatomical thinking, Calen also contributed to the development of pharmacology. His approach was holistic, believing that the best physician “was the one most capable of treating surgical conditions by means other than the knife, and particularly by diet and drugs.”[31] Although pharmacology (which is concerned with the uses, effects and modes of action of drugs) did not exist at this time, R.J. Hankinson would argue that this term can be appropriately used to describe Galen’s drug-lore as his was amongst the first attempts to collect remedies proven effective through experience.[32] Furthermore, he classified known materia medica by their power and effects in order to understand the interaction between the body and drugs.[33] Galen’s classification of drugs by their qualities and degrees and intensity were not abandoned until the nineteenth century, with the advent of new foundations of chemistry and molecular biology.[34] Drawing largely from ideas on drug qualities from the Hippocratic Corpus, Galen believed that a medicine would possess either a heating, cooling, drying or moistening effect.[35] The strength of this quality must then be determined as either weak, obvious, strong or massive.[36] In order to treat a patient effectively, Galen concluded that one must match a drug’s quality to the imbalance, and stressed the importance of the intensity of the drug being equal to the relative degree of imbalance otherwise there would be no healing effect.[37] Whilst this was a novel idea, the implementation of it was perhaps imprecise as the measurement of intensities were subjective.[38] Furthermore, Galen was restricted by the technology available and therefore lacked the technical means to measure the strength of a drug.[39] Regardless, over the course of his lifetime Galen produced eleven books on the Powers [and Mixtures] of Simple Drugs.[40] The first five books outlined humoral pharmacology, the other books contained a catalogue of healing drugs and their qualities, including a range of herbs, plants, earths, stones and animal products.[41] Whilst Galen ordered the first four books on herbs and plants in alphabetical order, it is clear that his thinking developed for the last two, ordering them by association. In total, he listed 440 plants and 250 other substances as remedies, detailing their observation and information on how to collect and apply them. Only a third of these possessed notes on intensity, which perhaps confirms the difficulty of subjectivity verses scientific measurement.[42] Despite this, it is clear from examining Galen’s efforts to change pharmaceutical and anatomical thinking, that he was an influential figure in the history of medicine.

The next half of this essay will examine the importance Galen’s contribution to the history of medicine regarding his own historiography and legacy. Galen created a considerable portion of literary output which commented on, and criticised both past and contemporary theorists.[43] One could argue that this motivated him to improve and develop existing medical knowledge, though it is questionable whether his genuine aim was to modestly instruct, or whether he hungrily desired to prove his supremacy. Rebecca Flemming states that Galen was “continuously engaged with the ideas and identities of his predecessors, trying to tie them all together in such a way so as to…produce his own.”[44] This study reflects the nature of his upbringing and training, and shows the beginnings of a progressive medical field. Certainly, Galen was fundamentally capable of progressing beyond his predecessors because of historical circumstances, meaning he did not have to revert to the basics as this had already been established for him.[45] Singer agrees with this, arguing that Galen systematised an existing body of knowledge and adapted it to fit his own theories.[46] Galen wrote many volumes on Hippocrates combined with his own anatomical researches, and understood that his interest in the history of medicine did not need to distract him from his own practical research.[47] Despite holding this opinion, Singer criticises Galen for unconditionally supporting his predecessors, believing that it was his “terrible dogmatism that held up the course of scientific research for centuries”.[48] Galen’s “avowed aim was to make clear to intelligent readers just what Hippocrates had meant in his writings, without necessarily entering into long discussion of the truth or error of each passage”.[49] As a result, Galen’s successors accepted his vision of Hippocrates “as gospel”, due to both Galen’s constructed authority and the credibility he bestows upon Hippocrates by reinforcing his ideas without investigating them further.[50] Therefore, Galen’s importance in the history of medicine is questionable with regards to his historiography as he inadvertently hindered the progress of medical innovation by placing too much legitimacy on the work of past physicians. This means that consequently, the physicians of the future did not dare to question their authority immediately as a result. Despite this, Galen was continuously involved with medical debates and used his book learning against his competitors by implying he could interpret the work of Hippocrates through a more precise understanding of the language.[51] Galen’s historiographic work is interesting, as he clearly uses the work of Hippocrates to promote his own, particularly his theories of the heart, brain and liver which he is keen to make agree with the latter.[52] This would prove advantageous in the medical profession, as a would-be patient would evaluate physicians based on their understanding of the theories of great doctors of the past.[53] Regardless of whether he temporarily postponed medical development with his dogmatism, Galen’s emphasis on the importance of physicians knowing about the work of their predecessors is important as this provides an arena for debate through which medical knowledge later flourished, after both Galen and Hippocrates’ ideas were re-examined.

Vivian Nutton argues that there can be no doubt of the extent of Galen’s success.[54] Hankinson disagrees with this statement, believing that whilst Galen personally strove to develop medical knowledge, it was “Hippocrates [who] sowed the seed, Galen [only] reaped the Harvest.”[55] Certainly, Galen would not have advanced as much as he did if Hippocrates had not previously done the groundwork for him. Although it can be argued that Galen’s “success” is proven by the test of time, his literary medical output (which is the most extensive surviving corpus of any ancient author, totalling 10% of what we possess of Greek prior to 350 AD) was preserved by others.[56] In the early stages of his career, Galen had no intention to publish his work; initially, he produced handouts to his students to assist their study.[57] These pages fell into the hands of “unscrupulous individuals” who passed his work off as their own.[58] After discovering “severely mutilated versions” of his texts with “all sorts of cut, additions and alterations” during his second period in Rome in 169 AD, he set out to revise them.[59] Many of Galen’s works were lost either by chance or deliberate selection. A fire in the Roman Temple of Peace in 192 AD destroyed the majority of his personal library.[60] Galen’s surviving Greek texts disappeared by 1200, such as the final six books on anatomical procedures, as they were too expensive to copy due to their size.[61] Therefore, these texts were not prioritised, particularly as dissection was effectively unknown, therefore their contents was deemed useless.[62] On the other hand, Islamic physicians recognised the importance of Galen’s work and began to translate his texts, saving them from destruction. Galen’s Examination of the Doctor is not known in Greek, but there are two surviving Arabic versions.[63] This placed a “Galenic stamp” on medicine in the Byzantium, Middle East and Medieval West.[64] As translation progressed, Galen’s ideas were transmitted back to Europe, and one would find it hard to dismiss the fact that Galen’s ideas constituted the basis of formal medicine in Europe until at least the seventeenth – possibly even the nineteenth – century.[65] However, Flemming, much like Singer previously, believes that Galen’s “imposing bulk of legacy” actually prevented, as opposed to invited, study.[66]Regardless, it is clear that Galen’s contribution to medicine is considered significant by medical institutions, as they still circulate Galenic terms such as “temperament” and “constitution”.[67] Furthermore, his emphasis on the importance of constant learning, training, and the acquisition of anatomical knowledge through dissection, has been a fundamental process in the development of the medical practice for almost two millenniums.[68] Ultimately therefore, I would argue that Galen’s total success and legacy was a product of a combination of his own medical research, and the efforts of others to preserve it.


In conclusion, Galen’s holistic approach to medicine with regards to study and treatment can be considered innovative, changing the nature of the medical profession. His emphasis on new methods of enquiry, particularly engaging with the physical world through dissection, undoubtedly enhanced existing knowledge on anatomy. Furthermore, with hindsight we could conclude Galen’s work on anatomy successful as it is known that his conclusions were based on the bodies of animals. However, it cannot be ignored that Galen’s inaccuracies, or rather his failure to state his source, potentially held up further anatomical research when the dissection of humans was available due to Galen’s imposing legacy causing later physicians to believe the human body had evolved, as opposed to condemning Galen as being wrong. Despite this, Galen was successful in starting to identify the nature and function of organs, placing them in the context of a wider, integrated system. Although Galen did make mistakes, these were due to legal restrictions as opposed to his incapability as a physician. Restriction also applies to his theory of drug qualities and intensities, as the technology to measure drug strength did not exist, however his contribution to this field was evidently significant as his method of classification was not abandoned until the nineteenth century, when this technology became available. Galen’s historiographic work emphasises the importance of learning and understanding the work of one’s predecessors in the medical field, however whether this can be deemed as a success is debateable due to him placing too much legitimacy on the work of past physicians such as Hippocrates which meant that, for a time,  it was too readily accepted as truth by Galen’s successors without further enquiry. Furthermore, it can be questioned whether Galen’s legacy is a result of his own hard work speaking for itself, or whether it is in fact due to the translation of Islamic physicians, particularly as Galen had no intention to publish his work in the first place. Despite this, we can conclude that Galen was ultimately was successful in presenting a new approach to the study and practice of medicine, largely through his emphasis on the importance practical investigation and holism, which would be invaluable to his successors.


Bynum, William. The History of Medicine: A Very Short Introduction (Oxford: Oxford University Press, 2008).

Bynum, William and Porter, R. eds., Companion Encyclopedia of the History of Medicine (London: Routledge, 1995).

Flemming, Rebecca. Medicine & the Making of Roman Women (Oxford: Oxford University Press, 2000).

Hankinson, R. J. ed., The Cambridge Companion to Galen, (Cambridge: Cambridge University Press, 2008).

Jackson, M. ed., The Oxford Handbook of the History of Medicine (Oxford: Oxford University Press, 2011).

Nutton, Vivian. Ancient Medicine (London and New York: Routledge, 2004).

Singer. P. N. trans., Galen: Selected Works (Oxford: Oxford University Press, 1997)


[1] P.N. Singer, ‘Introduction’, in Galen: Selected Works, trans. by P.N. Singer, (Oxford: Oxford University Press, 1997), p.vii.

[2] R.J. Hankinson, ‘The Man and His Work’, in The Cambridge Companion to Galen, ed. by R. J. Hankinson (Cambridge: Cambridge University Press, 2008), p.1.

[3] Rebecca Flemming, Medicine & the Making of Roman Women (Oxford: Oxford University Press, 2000), pp.260-261

[4] Hankinson, p.4.

[5] Flemming, p.257.

[6] Vivian Nutton, ‘Humoralism’ in Companion Encyclopedia of the History of Medicine ed. by W. F. Bynum and R. Porter (London: Routledge, 1995), p.287.

[7] Singer, p.x.

[8] Nutton, p.287.

[9] Flemming, p.277.

[10] Vivian Nutton, Ancient Medicine (London and New York: Routledge, 2004), p.237.

[11] Hankinson, p.9.

[12] Flemming, p.302.

[13] Flemming, p.255.

[14] William BynumThe History of Medicine: A Very Short Introduction (Oxford: Oxford University Press, 2008), p.15; Nutton, Ancient Medicine, p.236.

[15] Singer,

[16] Singer, p.xi.

[17] Singer, p xii.

[18] Julius Rocca, ‘Anatomy’, in The Cambridge Companion to Galen, p.257.

[19] Cited in Hankinson, p.13.

[20] Rocca, p.246.

[21] Flemming, p.267.

[22] G.E.R. Lloyd, ‘Galen and his contemporaries’, in The Cambridge Companion to Galen, p.36.

[23] Rocca, p.246.

[24] Hankinson, p.13.

[25] Rocca, p.246.

[26] Nutton, Ancient Medicine, p.237.

[27] Vivian Nutton, ‘The Fortunes of Galen’, in The Cambridge Companion to Galen, pp.374-375.

[28] Bynum, p.17; Nutton, Ancient Medicine, p.237.

[29] Bynum, p.17.

[30] Nutton, Ancient Medicine, p.238-239.

[31] Sabine Vogt, ‘Drugs and Pharmacology’, in The Cambridge Companion to Galen, p.304.

[32] Vogt, p.305.

[33] Vogt, p.305.

[34] Vogt, p.305.

[35] Vogt, p.308.

[36] Vogt, p.309.

[37] Vogt, p.309.

[38] Vogt, p.315.

[39] Vogt, p.315.

[40] Vogt, p.310.

[41] Vogt, p.310.

[42] Vogt, pp.310-311.

[43] Lloyd, p.34.

[44] Flemming, p.278.

[45] Flemming, p.278.

[46] Singer, p.xiii.

[47] Singer, p.xxiii.

[48] Singer, p.vii.

[49] Nutton, Ancient Medicine, p.225.

[50] Nutton, ‘Humoralism’, p.287.

[51] Singer, p.xxxv; Nutton, Ancient Medicine, p.225.

[52] Singer, p.xxiv.

[53] Nutton, Ancient Medicine, p.225.

[54] Nutton, Ancient Medicine, p.235.

[55] Nutton, ‘The Fortunes of Galen’, p.360.

[56] Hankinson, p.1.

[57] Lloyd, p.35.

[58] Lloyd, p.35.

[59] Lloyd, p.35; Galen, in Galen: Selected Works, trans. by P. N. Singer, p.3.

[60] Nutton, ‘The Fortunes of Galen’, p.356.

[61] Nutton, ‘The Fortunes of Galen’, p.357.

[62] Nutton, ‘The Fortunes of Galen’, p.357.

[63] Hormoz Ebrahimnejad, ‘Medicine in Islam and Islamic Medicine’, in The Oxford Handbook of the History of Medicine ed. by M. Jackson (Oxford: Oxford University Press, 2011), p.174.

[64] Nutton, Ancient Medicine, p.222.

[65] Vogt, p.355.

[66] Flemming, p.253.

[67] Nutton, ‘The Fortunes of Galen’, p.378.

[68] Ebrahimnejad, p.177.

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