Galen of Pergamum elaborated his medical philosophy during the second half of the second century AD, and was the dominant influence on medical thinking until the eighteenth. He was at the same time an experimental scientist, a medical practitioner, and a commentator. Before being doctor to the emperors in Rome, where he died, he was surgeon to the gladiators in his home town of Pergamum in Asia Minor. In his writings he speaks as the equal of Hippocrates, Plato, and Aristotle, praising and criticizing them by turns. If in many respects he was an epigone who selected from the immense heritage of his predecessors, he nevertheless codified their wisdom for succeeding generations, making considerable improvements in their views of anatomy and physiology.

He includes in his system ideas taken from Hippocrates, particularly the doctrine of the four humors. Where one of the most influential Hippocratic treatises, “On the Nature of Man,” held that four body fluids, or humors—blood, phlegm, black bile, and yellow bile—determined health, Galen extends this theory and speculates freely on different mixtures of the humors and types of temperament related to them. Galen also borrows from Plato the tripartite division of the soul into the rational, the passionate, and the concupiscent. Like Aristotle he believes that nature produces nothing in vain and explains the structure of each organ by its own final cause, and he follows the Stoics in attributing to the cosmic pneuma—an airlike substance—a primordial role in breathing and the conservation of life.

All these ideas, though they may not always cohere perfectly with one another, were organized and related by Galen in a way that both satisfied the demands of speculative logic and could be confirmed by sense experience. His system has survived in a large number of treatises, some better preserved than others, and these are only a part of his complete works. Each of these treatises merely develops one element in his vast scheme of medical philosophy, which we have reason to believe was constantly reshaped by its author to accommodate new observations and changing convictions. But the systematizing urge was already sufficiently strong in Galen for the Arab world and the European Middle Ages to give his doctrine a closed dogmatic form without feeling that they were distorting his thought. No doubt he owed his prestige to this excessive systematization; thanks to this his doctrine became the standard textbook of medicine, almost up to the final collapse of Aristotelian physics in the sixteenth and seventeenth centuries.

Nor did Galenism drop dead all at once. It was a vast edifice which only gradually crumbled away. It is not difficult to see in the writers who criticized the conservatism of Galenic orthodoxy considerable traces of the very doctrine they were attacking. Molière mocks his substantial qualities (the “dormitive virtue” of opium) and laughs at the “anticirculation” doctors who did not recognize Harvey’s discovery, but when he creates his misanthrope he makes him a melancholic, and his Tartuffe is a sanguine—in a word, Molière remains faithful to a notion of the temperaments which goes back by way of the standard formulas and systematic popularizations to Galen and more specifically to Galen’s commentary on Hippocrates. Toward the middle of the nineteenth century, at a time when Galen’s name was mentioned by no one but historians, there were still psychiatrists who asserted that the suppression of hemorrhoidal fluxes, of menstrual bleeding or of skin rashes, could cause a manic attack—and this relic of Galenism took some time to die out. So there was a considerable residue, but still only a residue.

One can see what a range of knowledge is needed to write the history of Galenism from its origins to its down-fall; the writer must be familiar with several cultures, and in addition must be able to assess the relations between different fields of learning which were once not separated by our disciplinary barriers: philosophy, cosmology, natural science, theology, literature, etc. Professor Owsei Temkin of Johns Hopkins is one of the few scholars of our time who could deal with so vast a subject, Going directly to the Greek, Latin, and Arabic sources, as well as to the mass of European medical literature, Temkin manages to bring to light the principal turning points in the transmission of Galenism, its social and religious implications, and the stages in its decline. Points of detail are dealt with in a substantial body of notes and a thirty-five-page bibliography quotes all that has been written on the subject.

In these four lectures (the 1970 Messenger Lectures at Cornell University) we find the simplicity and modesty of tone which is the prerogative of those who are completely in command of their subject and are thus best able to tell what in the present state of knowledge are the limits of our information, where further investigations are called for, and which of our conclusions still remain hypothetical.


For the historian of ideas the long history of Galenism is a perfect subject. It calls for an investigation both of the doctrines of a system and of the way it was received over a period of thirteen centuries. While we must naturally take into account what Galen’s system says, together with the various modifications of which it showed itself capable, we have also to take note of the way it was listened to, that is to say the function it fulfilled in the various milieux and institutions which accepted its authority. And finally, as with any doctrine which enjoyed a period of lasting supremacy before being eclipsed, we need to ponder the circumstances which led to its discredit and collapse; in such a post-mortem we cannot avoid characterizing it by contrast with the system which conquered and replaced it.

In his excellent account of Galen’s main ideas Owsei Temkin gives full weight to the notion of “cumulative progress” which was so important in his thought and attitudes:

His own generation has the advantage of learning “in a short time the useful things which were found over a long time, with toil and anxiety, by those before us.” If we only proceed rightly [Galen wrote], “nothing stands in the way of our becoming better than those before us.”

Galen sees himself as part of this scientific progress. He has discovered many things in anatomy of which those before him were ignorant, or which they stated badly….

Progress is not limited to the period between the ancients and himself; it includes his own efforts. Thus he has made new discoveries between the first and the second edition of his anatomical work. Altogether, he is restlessly at work to understand what he has not yet fully grasped.

But for Galen what was established by the ancients was no longer open to question. As Temkin writes of his philosophy, “Progress proceeds from principles rooted in ‘the ancients,’ and they have remained valid.” There could be no rejection of what was correctly stated in the beginning by Hippocrates and his school. According to this notion of “cumulative progress,” knowledge must be added to, but not totally reorganized. Galen’s idea of progress excludes the modern notion of the “scientific revolution.” As Ludwig Edelstein has shown, Galen believed in a “unified science,” a “scientia aeterna ruled not by sects but by truth only and receptive to contributions by anybody” (pp. 30-31).

Galen’s system is thus an open one and ready to receive subsequent additions, but it does not allow its foundations to be called in question. It is for this reason that over the centuries Galen could be invoked on the one hand by those who expounded a set of unquestionable “truths” and on the other by those whose experiments were finally to render obsolete the dogmas taken from Galen’s writing.

In its dogmatic version, Galenism is a coherent and simple system which is nevertheless capable of permutations which enable it to explain the most diverse phenomena. He taught that physics was based on four elements (water, fire, air, earth) and the four qualities (hot, cold, dry, moist). This served as a base for the physiology of the four humors and the pneuma; in Temkin’s excellent summary:

Obviously, excess or lack of humors causes disease, as do changes from the normal qualitative makeup of tissues or of organs. Not every deviation is a disease. There is a latitude of health, from the ideal condition to that where the functions are disturbed and where we can definitely speak of disease. Organs can, of course, also be diseased by anatomical changes leading to malfunction, and they may need surgical or mechanical therapy. But in most internal diseases treatment is dietetic or by means of drugs. Foodstuffs and drugs also have their qualitative compositions, so that the deviation of the body or of any of its parts can be changed by offering food, drink, and medicines of the opposite qualities….

He insisted on nine possible types of temperaments, i.e., qualitative mixtures: one, the ideal, in which all qualities were well balanced; four in which one of the qualities, hot, cold, dry or moist predominated; and four others in which the predominating qualities appeared in couples of hot and moist, hot and dry, cold and dry, or cold and moist. The well-balanced mixture served as the frame of reference for all others.

Since the system was capable of proliferation by analogy, many other doctrines came to be added to this basic core. The Middle Ages, partly because of Arab influences, established a rigid and simplified version of Galen’s original thought, at the same time superimposing on it a complicated set of astrological correspondences as well as recent ideas concerning the medicinal qualities of stones, the systematic use of cauteries, and intricate instructions for the correct position and time for bloodletting. However, this meant no fundamental change so long as the perception and interpretation of phenomena remained subject to the same concepts and the same code. The authority of Galen remained intact as long as elementary sense data (which “register” heat, dryness, etc.) were immediately translated into physical entities, which were then used to describe or explain the phenomena in question; the same applies to the relationship between the structure of the organs, as immediately perceived, and their function.


Indeed Galen’s explanatory system with its pairs of opposites, its homologies, and the possible permutations it offers is so closely related to our natural way of perceiving that it seems identical with it. So self-evident does it seem that we do not feel it to be an abstract structure or a replaceable tool; on the contrary, it infiltrates and governs our perceptions, and persuades us that in the very texture of what we feel or see we can have access to the secret inner structure of reality. Galen’s disciples found no difficulty in classifying natural drugs according to their heat, dryness, or moisture. Between the sensations we receive from an object and the concepts we use to interpret it there is only the tiniest of gaps and this is soon closed: a tactile or thermal impression is immediately read as a particular combination of natural elements.

For centuries, this translation of objects into the language of qualitative entities was not seen as in any way a naïve reductionism or a false simplification; it seemed that a complete and satisfying description of the constituent elements of an object had been given, and that there was nothing left to explain. Such is the case, we may add, in any system which invites us to perceive reality through categories which it has laid down in advance; such a system will never discover any objects other than those provided for in its code of classification, and in these objects it will never discover any characteristics other than those which can be accounted for by its codes of description. Only stubborn rebellious spirits dare to point out irreducible “facts,” exceptions to the general rule, phenomena which do not submit to the tyranny of a single scheme of interpretation. To go beyond this rebellious skepticism and suggest a truly new interpretation demands not only unusual courage and genius but a favorable socio-historical context.

One of Owsei Temkin’s most important remarks concerns the “totalitarian” nature of Galen’s doctrine—in one society this was a guarantee of its success, in another a sign of its inadequacy:

The history of Galenism, of its rise as well as its decline, shows, I think, that both assent and doubt on a larger than individual scale needed social incentives. Galen’s doctrines, as far as we can see, were not accepted piecemeal, but as a set, a philosophy. Seen retrospectively, Galen’s tendency to generalize formed a good deal of his strength. If instead of his comprehensive works and his attempt to set an example he had added a few more experiments, the total would probably have been lost in a time such as the third century. Within the structure of medieval Galenism physicians and patients found their way; it separated the doctor from the quack and gave confidence to him and his patient. The first major assault did not arise over specific points of anatomy or medicinal action; it attempted an overthrow of the whole, and it was fully equipped with a new theory, a new practice, and new social demands. [Pp. 124-125]

Galenic anatomy is incorrect on many points because it is based on the dissection of animals, but it was able to survive a series of modifications without being seriously threatened as a system. In the thirteenth century an Arab doctor, Ibn an-Nafis, contradicted Galen, denying the existence of pores in the interventricular septum and thereby demonstrating the pulmonary circulation. This discovery was quickly forgotten and its consequences remained unexplored; only in the twentieth century did scholars learn of this “precursor.” On the question of the soul and innate heat, the learned invoked Aristotle’s authority against Galen, but this had little effect on his system. In the sixteenth century Vesalius renewed the study of human anatomy, insisting on the importance of extremely precise graphic representation.* This showed that Galen’s authority was not infallible, and thus encouraged criticism in other fields, but it also fitted in with the old notion of cumulative progress and could thus be seen as more genuinely Galenic than the work of conservative doctors.

The age-old doctrine remained unshaken as long as the explanation of the causes of disease remained faithful to Galen’s model—i.e., the causes were explained by corruption of the humors and deviation from the correct proportion between them. Galenism survived as long as the art of medicine still attempted to counterbalance the mechanisms of disease by their opposites. In addition, his doctrine of psychosomatic correlations, placing as it did such heavy stress on the determining role of the “temperament of the body,” enabled Galen to attract followers among the free thinkers and materialists who doubted the immortality of the soul. The eighteenth-century atheists—La Mettrie in particular—were able to buttress their case with arguments taken from Galen’s treatise “That the Faculties of the Soul Follow the Temperaments of the Body.” If the doctrine of Galenism was bound up, for better or worse, with the medical establishment, it was often regarded as suspect by the religious establishment and in this way, paradoxically, it remained a living force by virtue of its polemic usefulness.

For Galenism to come under serious attack, there had to be a radical questioning of its physics and its physiology, in other words its interpretation of nature and its way of reading natural phenomena. When he rebelled against Galenism, Paracelsus, the sixteenth-century Swiss doctor and alchemist, was acting in accordance with the spirit of an age which rose up against all forms of established authority. But even if Paracelsus opened up new fields for mineral chemistry, his imaginary picture of the universe is swarming with innumerable occult forces. Since he relied on an intuitive vision of bodies and their secret properties, his teaching is less coherent and rational than that of Galen. He founded a rival school of thought, but his melange of magico-religious fables and valuable insights included no decisive facts which could have reduced Galenism to silence. The epistemological basis of Paracelsianism is shakier than that of Galenism.

In fact it was by its own weapons that Galenism was to perish. Temkin goes so far as to claim that it contained in advance all the concepts that were to contribute to its downfall by substituting for the cumulative ideal a more radical form of scientific progress. Indeed Galenism was over-thrown from within as soon as its own concepts and methods were employed in research based on a new discipline of proof and measurement. The decisive turning point came when Galen’s techniques and forms of reasoning were applied in conjunction with new rules of procedure and a new ethics of experimental verification. Galenism succumbed not to a resolutely hostile doctrine, but to those who were seeking to check its conclusions by new, independent, and more accurate experimentation.

Galen had experimented with ligatures, particularly on the ureters, but also on the arteries, “to demonstrate the provenience of the pulsatile force.” In the seventeenth century William Harvey proceeded in just the same way; he too experimented with ligatures. How was it then that he made a discovery which Galen overlooked? Probably because he calculated with greater precision the systolic flow produced by the left ventricle at every stroke. But also no doubt because he organized his experiments in a more “abstract” and limited way, so that nothing else was involved but the movement of the blood.

Temkin’s hypothesis here is very persuasive: for Galen the problem of the blood was inseparable from those ecological and dietetic preoccupations which were so important to the Greeks. His thought centered on the transformation of food and the formation of the blood, on the air or pneuma which was inhaled and its effect on innate heat. Because he always gave first place to the complex relations between the body and its environment, and did not consider the movement of the blood as a closed mechanical system, Galen failed to observe the circulation of the blood, even though it was within his reach. For Harvey on the other hand the problem of circulation could be approached simply as a limited problem in elementary hydraulics.

Galen had speculated about the quantitative differences in heat which distinguished various morbid states from the state of health. But his notion of quantity derived from a qualitative impression, subjective or tactile, of heat or cold. His doctrine tried conjecturally to establish a hierarchy of “degrees” of sickness and to find a range of warming or cooling drugs which would correct by contraries the excesses caused by “distempers.” When at the beginning of the seventeenth century Sanctorius made the first tentative attempts to measure temperature he intended no more than to add his contribution to Galenic medicine. But in fact he contributed to the decisive separation between qualitative estimates and measurements based on instruments; he severed the different elements which had been interwoven in the Galenic system: supposedly measurable qualities, simple arithmetic applied to creations of the mind, imagined deviations, etc. In this manner Sanctorius opened the way to a mechanistic approach to physiology and medicine.

Did this mean the end of Galenism? Certainly Cartesian mechanistic philosophy would have nothing to do with final causes, which were an important part of Galen’s teaching. But the mechanical explanation that Descartes tried to put in the place of Galen’s “occult qualities” was often no more than a translation of Galenic physiology into a new language. Descartes’s “animal spirits” only differ from those of the popularized Galenism of the Middle Ages in the greater stress laid by Descartes on the technological model of distillation, which was supposedly needed to produce them. Descartes’s mechanism of the movement of particles is just as conjectural as Galen’s arithmetic of combined qualities. Nevertheless the great advance of Cartesianism was the hypothesis of a world in which everything proceeds “by figure and movement”—if one does not go beyond mere qualitative sense impressions one remains in the realm of illusion. Hot, cold, dry, and moist are not physical entities for Cartesian science but only subjective sensations of no scientific value. Owsei Temkin rightly says that “the metamorphosis of objective qualities into subjective qualities was as destructive to Galenic science as doing away with fire, air, water, and earth as chemical elements” (p. 161).

The Cartesians’ mechanistic models (animal-machines, man-machines) soon lost their value as guides to knowledge and were seen to be irreconcilable with strict experimental method. This premature mechanization of the biological sciences, in which the spirit of geometry overwhelmed the need for proof, came to be rejected toward the middle of the eighteenth century, for it too led to a reading of phenomena through the spectacles of a reductive interpretative scheme. Instead of invoking hot, cold, dry, and moist, it spoke of fibers being more or less taut. Cartesian science replaced Galen’s explanations of fever with the notion that the blood became heated by rubbing against the artery walls. The vitalist thought which at the end of the eighteenth century insists on the irreducible difference between the organic and the inorganic, and takes up the old tradition of final causes, is in fact a secret revival of the teleological philosophy of Galenism. But now it is an unconscious Galenism, or at any rate a Galenism which prefers to go under another name, since there is no advantage to be gained from being associated with a name so long linked to medical conservatism.

This was equally the case at the beginning of the nineteenth century when Bichat developed his theory of tissues; it would have been unwise to connect it too openly with Galen’s doctrine of “similar parts” (bone, skin, muscle, tendon, fat, cartilage), which prefigures it almost word for word. Scientists preferred now to appeal to the authority of direct observation, experiment, and analysis, not going beyond observable and verifiable facts. Does this rejection of conjectural interpretations imply that like Emile’s vicaire savoyard they had decided to “set aside all books”?

Paradoxically there is one name which outlives that of Galen, and this is Hippocrates, whose “works” Galen had commented on and sometimes criticized. Thanks to an idealizing process which neoclassicism had already displayed in Winckelmann’s theory of art, Hippocrates came to be seen as the genius par excellence, the unblinkered observer who dares to look at nature directly and writes down what he sees, noting and comparing the facts without submitting them to causal interpretation. The “founder” of medicine thus became for an entire generation the venerable patron of a scientific revolution whose consequences were to effect a clear-cut separation between modern medicine and everything the ancients had ever said about health or sickness; this was the beginning of an age of progress in which science is no longer cumulative but is constantly redefining its principles and its methods.

For a certain period Hippocrates was no more than a glorious name which the new clinical medicine used to cover its refusal of all the old causal interpretations and its renewed inquiry—working with different tools in a new sociocultural environment—into the visible signs of illness. Thus this return to origins, like the other revivals of the neoclassical age, was simply a preparation for the imminent discovery that there is no returning to the simplicity of our beginnings.

(Translated by Peter France)

This Issue

June 26, 1975