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1.2 The significance of the doctrines of Plato and Aristotle in shaping Galen’s views

The medicine of the authors of the Hippocratic Corpus was already a sufficiently mature discipline which offered skills for critical thinking and systematisation of empirical experience. However, the system of Hippocrates’ views was far from dominant—it had plenty of opponents among physicians of the civilised oecumene. The shortcomings of his system were obvious and were defined by the lack of a theory of natural philosophy, which could have offered a global world view and methods of obtaining knowledge about it, which could match the tasks of medicine. This world view was supposed to meet a variety of explanatory tasks—from questions about the origin of matter in general to the specific physics of the human body.

The critical components of this system of natural philosophy, which formed an adequate world view of medical researchers, were proposed by Plato and Aristotle It is particularly through the merging of the doctrines of two of his great predecessors that Galen created medicine as an integral scientific-practical system. It is no mere chance that one of the principal treatises of Galen is titled “On the Doctrines of Hippocrates and Plato”.

Plato’s legacy is the great phenomenon in the history of civilisation. A lot has been written about it. The same applies to Aristotle (probably even to a greater extent). In a concise way, I will try to demonstrate the significance of the Academy and the Lyceum in the formation of a proper world view and the type of rationalism typical for a physician in the Hippocratic tradition.

Plato learnt medicine from Philistion, with whom he got acquainted on his way to Magna Graecia. Philistion was born and raised in the Southern Italian town of Locri. He built a remarkable career and by the time he met Plato, he was the personal physician of the tyrant of Syracuse Dionysius II. Living in Sicily, he was of course influenced by Empedocles’ doctrine of the primary element, which had a determining influence on his views about general pathology. Philistion had a reputation as a staunch anti-Hippocratic, although the essence of his dispute with the famous physician from Kos is unclear based on surviving sources. We can only indirectly make judgements about it based on fragments of texts from the Hippocratic Corpus where disagreements with the ideas of Empedocles are expressed.

Plato’s views on the problem of medicine are primarily laid out in Timaeus and pertain to a wide range of issues—from anatomy and physiology to the problem of the unity of the corporeal and the spiritual. Among other things, Plato offers his classification of diseases, clearly defined under the strong influence of the ideas of Philistion. Plato suggests that there are three types of diseases. The first group is defined by the disruption of the equilibrium of the four primary elements—earth, air, fire and water. Excess or deficiency of any of the elements in the body gives rise to processes leading to the decay of health.24 Plato associates the second group of diseases with disturbances in the nourishment of parts of the body. Based on the assumption that blood is directly formed in the liver from digested food, Plato reaches the conclusion that blood contains all substances necessary for the body. Sinews are formed from fibrins and other substances of clotted blood. With normal blood supply, flesh produces a certain viscous fluid which attaches it to the bone and nourishes bone matter and bone marrow. Unless the structure of nutrition is disrupted, the blood always has enough of the necessary “building” material to form and restore various tissue. The disturbance of nutrition causes disease—flesh decomposes, releasing products of decay into the blood. Blood changes colour, becomes bitter, acidic and saline. Decay products destroy it and, spreading through veins, disrupt the nourishment of flesh. Decay and decomposition processes spread.25 Diseases of the third group are associated with the imbalance of humors and primarily arise from the disturbance of the breathing process. The aim of breathing is to cool the inherent heat generated by the body. Breathing may occur through the lungs and special pores in the skin. If the work of the lungs is impeded by excess humor (for example, phlegm), the breathing process occurs in a different way and to a greater extent than naturally. As a result, natural metabolic processes are distorted, and decay processes arise in those parts of the body with respect to which respiratory functions are not properly occurring. A characteristic feature of such diseases is excessive perspiration caused by excess heat in the body.26

This classification reflects the considerable influence of the views of Empedocles and Philistion. According to Empedocles’ theory of digestion, food is broken down into small particles in the mouth, then under the effect of internal heat it is digested in the stomach, broken down into its constituent elements, which are then carried into the liver where they turn into blood. Therefore blood contains all substances necessary for the vital functions of the body. These substances move in the human body with the flow of blood and are absorbed by tissue according to the “like attracts like” principle. If, for example, the primary element of “fire” is dominant in the bones (after all they are dry and hard), then this primary element comes from the blood and most of all enters the bones in particular, etc. Plato also follows in the tracks of Empedocles when it comes to ideas about flesh as a secondary formation which originates from blood. However, the definitive articulation of the theory of disease can be considered Plato’s own discovery.27 Thanks to Plato, the theory of the four primary elements, which was subsequently supported by the peripatetics, held a dominant position in science for centuries. Equally important for the development of rational medicine is Plato’s cutting loose of all elements of mysticism and deification of the primary elements, associated with the idea that they are constantly undergoing a process of morphogenesis. In his system, the four primary elements become simply physical phenomena, clearly associated with empirical practice and taking their place in the global world view created by Demiurge God based on defined laws. Here Plato’s natural philosophy aligns with the views of Hippocrates who intuitively, based on practice, arrived at the perception of the profound functional purposefulness of the human body. They have a common enemy—sophists and mystics, who misinterpreted Empedocles and claimed that nature is a blind and irrational force. Plato understands very well the universal nature of the matter under consideration, which is why in Timaeus he considers it necessary to clearly define the place of the primary elements in the general system of natural philosophy. Here the significance of primary elements is reduced from the sources (as is the case with Empedocles28) to some kind of building material: like an architect, the Demiurge builds the world in general and human body, in particularly, according to a certain design using the necessary components.

Note two critical components of Platonic physics: first, the primary elements can be transformed into each other, changing their intrinsic properties; secondly, the description of these properties is given in the language of mathematics. The foundation of Plato’s idea about the vital functions of the body becomes the teleological principle—the purposiveness of function and, consequently, anatomy. The ontological foundation of the human body is an Act of Divine creation of ordered matter which functions according to defined laws incorporated in it. The theory of the primary elements becomes a critical part of the description of this structure. However, there was need for a systematic, consistent description of the movement of primary elements in the human body. After all, it is clear that the human being grows and develops, ages and dies; certain metabolic processes occur in his body, and this indicates the presence of changes. The Aristotelian system (with the exception of the doctrine of the creation of the world, of course) was subsequently built on this assessment and the description of the body in the categories of the laws of motion of matter.

Plato solves the task of describing this dynamic using mathematical analogies—this reflects the clear influence of Pythagoreans. Plato also needs mathematical analogies to describe the act of the creation of the universe by the Demiurge.29 The subordinate, secondary nature of the primary elements in Plato’s cosmology is emphasised from the outset: the Demiurge brings them to a certain order described by geometrical shapes and numbers. The universe in Plato’s cosmology is described by a three-dimensional coordinate system. Therefore particles of each building element must be formed by Supreme Intelligence in a defined mathematical form, exist in an ordered physical world, change and interact with each other purposefully—in accordance with the laws of the functioning of natural bodies set as the foundation of creation by God. Here Plato challenges the basic principle of atomism, so well-liked by many sophists—the mechanically random nature of the motion atoms. The theory of possible transformation of primary elements is extremely important for the history of medicine. It exactly enables to view the human body as a dynamic system. In the final part of Timaeus, Plato transitions from the macrocosm to the microcosm, i.e., the structure and functioning of the human body, which he describes using the same teleological, axiological and physical principles. Here Plato is decisively at variance with Empedocles in substance: he places the centre of rational activity, higher control of the functions of the body in the brain. According to Empedocles, this centre is located in the area of the heart, which goes together with the great significance of blood and blood supply in his system.

The geometric analogies Plato uses to explain the motion of particles of primary elements are of exceptional interest. Organs consisting of smaller particles are impermeable for larger particles. Anatomical structures consisting of larger particles are permeable for smaller particles.30 Plato even explains functional processes in the body in the language of geometrical shapes. He presents primary elements in the form of various geometrical shapes: fire as a tetrahedron, water as an icosahedron, air as an octahedron and earth as a cube. For example, the element of fire exists in the form of the smallest, all-permeating particles, which as it were “cuts” with its “tetrahedron” the links between the primary elements into which broken down food in the stomach disintegrates. Plato illustrates this penetrating power of fire and air, created by God to carry out fundamental physiological processes, using a “fish-trap”—a peculiar model of the human body.

Similarly, in the language of mathematics, Plato attempts to explain the processes of growth and aging of the human body. A baby is conceived when the male and female seeds of the parents are fused. The triangles of the elements constituting the body of the baby or young person are free of foreign inclusions, some kind of “stuck dirt” and are tightly attached to each other. Damaging factors in the form of the flow of elements from the outside (including those coming from food) are structurally weaker than those constituting the inner core of the body tissue of a young person. Plato interprets the aging process as the “slackening of the roots of the triangles of the elements”, leading to the loss of structural solidity of the tissue. They are therefore easy to separate. They lose their ability to withstand external effects. The body is damaged and ages.

I see a lot in common between the interpretation of the principles of general pathology by the authors of the Hippocratic Corpus and Plato’s reasoning. First of all, this pertains to regarding disease as a quantitative category, when a healthy body and a sick body have the same components, but with excess or deficit of some of the components. Secondly, this is the interpretation of the state of “good mixture” of elements (“crasis”), which accompanies health, and disruption of their mixture (“dyscrasia”). The most striking similarity of the thought process of Hippocrates and Plato is seen when analysing the third class of disease caused by the imbalance of the liquids: Plato describes the origin and properties of phlegm and both types of bile, enough to understand their pathological influence on the functioning of the human body.

A critical component of Plato’s philosophy is the concept of the mutual influence of the spiritual and the corporeal (in the modern sense this is called the psychosomatic integrity of the human body). Diseases of the soul, according to Plato, do not have a divine origin and are explained by a defective inherited constitution or bad upbringing. Psychosomatic integrity in his system has a physical explanation: parts of the soul located in corresponding parts of the body are associated with them. Hence the processes of aging and disease of the flesh also affect the spiritual life of the human being. As a result, inflammation of brain tissue, which is the cause of fatal diseases, is so dangerous, particularly because in this case the bonds between the substance of the superior, immortal part of the tripartite human soul and its repository—the brain—weaken. Therefore, since death arrives the moment the immortal part of the soul separates from the body, any local damage to the brain in which the Demiurge placed the immortal soul means an unfavourable prognosis of disease in general. Sacredness in this case is determined by the significance of the phenomenon—after all bodily death indicates the act of final separation of the immortal part of the soul and the body. Inferior parts of the soul also die with flesh, and the habits of the human being vanish with them too. It is interesting that we see these ideas of Plato developed by Galen: he views the inferior parts of the soul as substantially similar to the structure of those organs in which they are located.31

There was a tradition in European historiography to criticize these ideas of Plato as rudimentary and incoherent compared to the Hippocratic Corpus.32 It is impossible to agree with this criticism: I see considerable congruence between the views of Plato and those of the authors of the Hippocratic Corpus. Furthermore, this congruence does not surprise us, even considering Philistion’s reputation as an obvious anti-Hippocratic. How exactly was the disagreement between Philistion and Hippocrates supposed to manifest? It is usually regarded that medicine at this time was dominated by two opposing schools—dogmatists and empiricists. Summarising the characteristics of these schools, we may get the following: empiricists rejected the value of theory and the resulting principles of studying anatomy and physiology, extolling the significance of everyday medical practice; dogmatists in turn advocated for the need for a systematic approach to diagnosis and treatment of diseases. Of course, it reflects a longer historical perspective: this is a conflict between “theoreticians” and “practicians”. But how this contradiction could look like in the past? However, does this mean that, for instance, Philistion rejected Empedocles’ system and Alcmaeon’s views, regarding them as theoretical or denied the treatment of the opposite with the opposite, believing that Hippocrates did not substantiate it theoretically enough? The negative answer to this question is obvious considering the observations made earlier. Furthermore, remember that by all accounts, the Hippocratic system was characterised by priority attention to the results of the practical work of the physician and the rejection of abstract sophist theories. So, what is the difference?

In my opinion the right answer lies in treating medicine as a theoretical-practical system which progresses along the path of accumulation of knowledge and its generalisation. This in turn determined the need to turn to anatomical dissections (we see some of their descriptions as early as the Hippocratic Corpus). We see the further conceptualisation of rationalist dogmatists through the excellent examples of Herophilos and Galen.

Sometimes Galen’s philosophical views are called “eclectic”. However “eclecticism”, “eclectic system” basically means the mismatch between the philosophy of a thinker who proposes a new global theory with taxonomic ranks more developed with respect to his predecessors and not-every-successful contemporaries. The medical ideas of Plato may also seem “eclectic” because they combine elements of the ideas of Empedocles, Diogenes of Apollonia, Alcmaeon, etc. One can certainly speak of the incompleteness of Plato’s medical theory—it does not encompass all problems associated with solving tasks facing the doctor. Nevertheless, it is clear that Plato proposed fundamental principles which shaped the foundation of the theory of ancient rational medicine. The idea of a tripartite human soul and the placement of its superior, immortal part in the brain turned out to be particularly fruitful. This idea particularly defined further anatomical and physiological studies and subsequently enabled Galen to outline basic methodological categories in his medical system.33

In his commentary to Timaeus, Galen pays considerable attention to the functional explanation of the model proposed by Plato:

It may be recalled that, according to Plato, we need to imagine that the whole of the greater weel is the outer covering of the body, which constantly interacts with the outside air. Within it, it contains two air-filled vessels akin to smaller weels. One of these is located in the abdominal cavity, and the other in the chest. The whole space between the greater weel and the lesser ones is filled with rays of fire running along the arteries and veins, while the cavities themselves assist in movement from the inside outwards, and from the outside inwards. Accordingly, Plato says that there are two opposite movements in the two smaller weels. One is directed towards the outside air, and the other, correspondingly, from the outside air inwards. Next, Plato explains to us how these movements take place, and why they do not stop for as long as the body is alive. Summing up his ideas, he says that this double movement creates a double process of respiration and a double process of nutriment distribution. I, however, call respiration a function consisting of inspiration and expiration, and in this I agree with all physicians, that there are three states: the first is movement inwards, the second is movement outwards, and the third is the result of these movements. Hence, the first form of movement is ‘inspiration’, the second is ‘expiration’, and respiration itself is the result of these movements. Plato calls breathing in respiration and says that air passes through the trachea and, evidently, enters the abdominal cavity. He believes that the movement of air outwards and inwards takes place in the cavity within the greater weel and the lesser weels there. When food and drink enter, they are crushed and broken up into particles, after which they are dispersed throughout the body as heat and pneuma with the help of the network [of the vessels]. Physicians call this process the distribution through the body of nutriment, which reaches every part of the body via the arteries and veins. Plato then states that this is the reason for the double movement of pneuma and heat. (Comm. Tim. 78d2-79a4)34

The above-mentioned “fish-trap” as a mechanical model of human body consists of two inner chambers placed one on the other. The Demiurge creates the outer, first mesh from the element of air and the inner one from fire. There is not one, but two funnels at the entrance of the fish-trap, one of said funnels being bifurcated. This indicates the openings through which air and food enter the body. The bifurcated respiratory funnel corresponds to the entrance of air through the nose and the mouth—otherwise it would be impossible to breath while eating. The extension of the lower parts of the two upper funnels signifies the formation of the oesophagus and the trachea with bronchi. Inside the large fish-trap there are smaller ones, which can be entered through funnels—one small fish-trap corresponds to the the lungs, and it can be entered via the trachea and the bronchi, and the other through the stomach, or more precisely the digestive system. The space between the large and small fish-traps is the flesh—muscle tissue penetrated by blood vessels.

Galen explains that the inner “fire” (or inner heat) is the primary source of energy of physiological processes. Even the red colour of blood is a result of this “fire”. The need for constant nourishment of tissues and organs of the human body is due to the loss of nutrients in the life process. This loss is also the result of external attacks of streams of elements existing outside the human body. We take note of Galen’s remark on “double breath” and remind that skin metabolism is of great significance in modern physiology, and the expression “cutaneous respiration” sounds quite scientific from the perspective of modern medicine. Galen’s commentary provides a clearer understanding of the concept of “fish-trap” laid out in Timaeus particularly as part of medical theory. Galen advanced Plato’s fundamental ideas about medicine the furthest and laid them bare from a practical point of view. It is particularly Galen’s train of thought that helps us unravel the gnoseological meaning of Plato’s ideas.

The breathing process constantly sustains the unstable energy of the inner “fire”, which in turn provides the energy of the digestion process. Food is digested in the stomach under the effect of inner heat—the physics of this process become fully clear if the process is considered a combination of the stimulating effect of inner heat and mechanical movement of the smallest particles of fire. The same energy facilitates the movement of blood formed from food particles through the veins. The respiratory function is realised according to the “circular thrust” principle, when, under exit pressure, surrounding air is moved, and successively, by transferring this forced action, generates circular movement, also entering the body through pores in the flesh. Plato argued that breathing has a special purpose, regulating the intensity of internal heat (element of fire). Although he never explained how he sees anatomical interconnections of the two fish-traps with respect to the circulation of blood, which contains elements for nourishing tissues, through the veins. Plato argues that lungs were meant to cool the heart, and air enters the lungs cold and is subsequently heated. It is assumed that the air also comes out through the pores heated by the inner “fire”. Galen rightfully observes that breathing is the exchange of air with the environment in the form of a series of half-turns in opposite directions, in accordance with rhythmic changes in air flow. He explains that the inner “fire” (or inner heat) is the primary source of energy of physiological processes. The need for constant nourishment of tissues and organs of the human body is due to the loss of nutrients in the life process. This loss is the result of external attacks of streams of elements existing outside the human body. All of this depend upon circulation and activity of “fire” element.

Plato describes the topography of the human body, which consists of cavities which accommodate organs according to their importance (due to the locations of various parts of the soul), which enables to determine the peculiarity of each and identify the laws of their interaction as a whole.35 He illustrates the duality of the structure of the human body, which manifests in the functional peculiarities of its organs, which are in constant motion: on one hand, necessary functioning, i.e., striving for health, and on the other hand—constant threat of “disorder” (disease). The duality of the structure of the human body is also exhibited in the movements of elements inside the complex system of the fish-trap in the form of the combination of flow and counterflow (i.e., movement in opposite directions) (Comm. Tim. K78d2-79a4).36

Plato’s doctrine on human nature is based on the idea of of the tripartite nature of the human soul. The primary function of the superior, rational part of the soul is intellect and control of voluntary movements of the human body, similar to the movements of intellect and influencing the preservation of the order of elements, and, as a result, the preservation of health. The property of the rational part of the soul is its immortality. Therefore the state of the physical death of the human being is described through the separation of the immortal part of the soul and the body, which ends with death, which is definitively understood as agony, the separation of the superior, immortal part of the soul from flesh. Taking cue from Plato, Galen argues that:

Reason resides in the brain, from which it controls the nerves and movements, as well as the five senses. The appetitive part of the soul is located in the liver and is responsible for the blood, veins, and also has the ability to differentiate substances necessary for the nourishment of the body. The spirited source, which is located in the heart, monitors the arteries, the natural temperature, pulsation of the blood, as well as the animal part of the soul. (Comm. Tim. 76е7-77с5)37

Plato’s idea of the tripartite nature of the human soul turned out to be exceptionally productive for the development of medicine. The names of two lower parts that have been established in historiography are—“animal” and “vegetative” (as synonyms of the terms “spirited” and “appetitive”)—are not random. Plato points (and in his commentary, Galen stresses the same point) to the unity of the creation of the living: animals and plants have corresponding inferior parts of the soul, which the great philosopher considers mortal. Animals have two—spirited and appetitive—parts of the soul, and plants have only one, inferior part. The presence of two parts of the soul explains their similarity to man: the substance of their structure is made from the same primary elements and is animate. Plato’s system therefore solves the task of the demarcation of what in contemporary science is referred to as organic and inorganic structures. This is confirmed empirically: the entire physical world consists of the same primary elements, but the human being cannot feed38 on, for example, fragments of volcanic lava or sand, but can eat animal meat and plants. This question can be resolved through Plato’s theory, which endows animals and plants with inferior parts of the soul, which allows for the use of similar substances for the nourishment of human body tissue. Commenting on Plato, Galen notes that his predecessor “pointed out that desiring capacity of the soul is equally inherent in all living beings and plants” (Comm. Tim. 76е7-77с5).39 The key to this dilemma, to my point of view, is exactly the physiological role of the parts of the soul—the influence of different sorts of pneuma makes the elements to become part of metabolism.

The idea of the unity of creation and the functioning of all living organisms, which is typical for Plato’s system, is significant for medicine. These ideas subsequently shaped Galen’s views on the relationship between the spiritual and the corporeal in the context of understanding their unity in health and disease. The ideal of this unity is harmony and balance of the physical state of the body (variable in nature and ultimately mortal) and the soul, which, in its superior part, is immortal and immaterial. The unity of the spiritual and the corporeal cannot be formal; it should be substantial, essential in nature, which Galen pointed out in his commentary:

What only remains is to point out to those who consider that our soul has one essence, which holds in itself three potential facilities—rational, spirited (θῡμοειδής) and desiring (ἐπιθῡμητικόν). It would be reasonable to argue that the three parts of the soul are in fact one essence. Plato points to the difference between the rational soul and unconscious spiritual phenomena; therefore reason is in a state of battle with the desiring and spirited parts of the soul. Furthermore, the rational part of the soul sometimes seeks the help of the spirited part in order to resist the desiring facility. Plato only points to these types of soul, but does not speak about them as one essence. Even if the essences of the soul were different, they would still be present in all internal organs, and so any one of us can claim that we have not three souls, but three properties of one soul. (Comm. Tim. 76е7-77с5)40

The historical evolution of Plato’s idea of the mutual influence of the spiritual and the corporeal formed Galen’s concept of unity of soul and body, and, further, led to the emergence of the modern concept of the psychosomatic integrity of the human being. In light of this detailed description of Plato’s views on the anatomy and physiology, the three groups of the development of disease he proposes become clear. Psychosomatic integrity has its physical explanation: parts of the soul located in corresponding organs are closely associated with them. Hence the processes of aging and degradation of flesh also affect the spiritual life of the human being. Inflammation of brain tissue, which is the cause of diseases which threaten human life, is dangerous particularly because in this case the bonds between the substance of the superior, immortal part of the tripartite human soul and its repository—the brain—weaken. Plato does not consider epilepsy something supernatural and shares Hippocrates’ view on this matter, mocking the name “sacred disease”, pointing out its appropriateness only to the extent to which sacred substance is the brain matter it afflicts. Sacredness in this case is determined by the significance of the phenomenon, after all bodily death indicates the act of final separation of the immortal part of the soul and the body. The death of the inferior parts of the soul (spirited and sensuous) along with flesh is clearly defined here. Again, it is interesting how Galen further develops these ideas of Plato: he sees the inferior parts of the soul as substantially similar to the structure of those organs in which they are located.