FROM PLATO TO PRAXAGORAS

The Roman author Celsus praised Hippocrates as the first to separate medicine from the ‘studium sapientiae’, the study of wisdom, or, as we would say, ‘philosophy’.1 If he intended by this to suggest that after Hippocrates medicine and philosophy went their separate ways, and that neither learned or borrowed from the other, he was considerably mistaken.2 Even as some of the texts in the Hippocratic Corpus were being composed, the philosopher Plato was making use of medical data for his own philosophical purposes, as well as putting forward an explanation for illness that was to have a long-lasting impact on the intellectual world. We have already seen that Plato referred on several occasions in his dialogues to Hippocrates as the leading representative of medicine of his day, and in his Second Letter he mentioned his own acquaintance with the doctor Philistion of Locri.3 His letter expressed the hope that Philistion would be allowed by his master, the tyrant Dionysius II of Syracuse, to come to Athens, although whether he ever did so is far from clear.4 Plato is known to have made three visits to S. Italy and Sicily, in about 387, 367 and 362 BC, and may well have met with Philistion on any of these occasions. However, the authenticity of this letter has been frequently called into question, and a link between the two men could easily have been a later rationalisation of the ways in which some of Plato’s theories come very close to those of Philistion as reported in the Anonymus Londinensis papyrus. Philistion believed in three general causes of disease, which he then subdivided. The first (internal) cause was an excess or a deficiency in one of the four ‘forms’, hot, cold, wet and dry. The second (external) was the presence of wounds or sores, or the result of an excess or deficiency of external heat and cold, of inopportune changes from one to the other, or simply of wrong nutriment. The third and last cause was some impediment to the flow of air into or out of the body.5 In his Timaeus, Plato produced two explanations that are very similar to the first and last of Philistion’s: imbalances and irregularities within the four elements, and the failure of air to move properly into and out of the body. Where there is no breath, the body begins to rot; where there is

too much, the air forces its way through where it should not, and causes painful swellings, sweatings and distortions.6 But Plato is not simply repeating Philistion; alongside breath or air he sets the far more traditional pair of bile and phlegm. His second cause goes even further in its apparent independence from what others had said before him. The Platonic body is built up from the four elements, earth, air, fire and water, which form the building blocks from which everything else is created. Flesh and sinews are formed from blood – itself the direct product of ‘digested’ food – and its constituents, and the ‘viscous oily substance that comes from the sinews and flesh’ nourishes the outer part of the bones, while a pure substance nourishes the marrow.7 When this process is working correctly the patient is healthy. But it can go into reverse. The flesh can decompose, the blood become bitter, and bile, serum, phlegm and the like can then destroy the whole body. Instead of nourishing the body and benefiting from one another, they are carried round the body in the veins, spreading destruction and decay in mutual conflict and strife.8 When the fluid that binds flesh and bone together dries out, the corrupted substance crumbles away and flesh and bone become separated. When the very marrow becomes affected, through some excess or deficiency, even more serious diseases occur. The deeper and more advanced the degeneration, the less the chance of recovery.9 Whether this concept of what might be termed diseases of decomposition is Plato’s own or draws on an earlier philosopher or doctor is not clear.10 It creates a powerful image of the body going into reverse, almost spontaneously. Earlier in his argument, Plato had explained growth and decay as the result of the vigour of the triangles that, in his mathematical universe, lay at the very foundation of all matter. When young and fresh, their edges are sharp, capable of prevailing over those that occur in food and drink, and so cutting up that material into its basic constituents, which can then be distributed efficiently around the body in blood as nutriment. The new triangles can attach themselves to the appropriate parts of the body and cause it to grow. Conversely, as we grow old, the triangles become blunter and lose their cutting edge; they themselves become more easily divided, and the body descends into old age. When the bonds of the triangles that make up the marrow can no longer hold together, they come apart, releasing the bonds of the soul, which flies off. This is the normal process of ageing and death. To what extent, if at all, the same process is followed in diseases of degeneration is far from obvious, and Plato does not explain what triggers such diseases.11 The descriptions of these diseases are all the more striking because they reverse the whole construction of the body so carefully and purposefully organised by Plato’s Craftsman (the Demiurge or Creator). From marrow, the most important of all tissues, is formed the brain, and other parts are enclosed in bone to form the spine; after bone is formed flesh, which is carefully distributed around the body according to the design of the Creator. Because solid bone and thick flesh inhibit sensitivity, he reduced the thickness of the

bones of the skull surrounding the brain, the seat of the intellect. The consequent loss of protection and the possibility of increased pain is more than outweighed by the gain in sensitivity.12 The neck, through which only very tiny channels go upward to the head, further protects the brain from the deleterious polluting effects of the mortal elements of the soul which are located further down in the body.13 Plato’s description of the human body in the Timaeus, which exercised a powerful influence over later thinkers, owes less to his acquaintance with the internal anatomy of the body (or with earlier writers on this theme) than to his own preconceptions about the soul. In the Republic he had exploited a complex series of mutually reinforcing analogies between the city and the soul to argue that there were three parts to the soul, concerned, respectively, with reason, spirit or energy, and desire. In the later Laws he drew parallels with the doctor’s knowledge and practices to support the authority of the philosopher to legislate for the unhealthy city.14 Just as in the healthy or just city all its citizens had to work together, each doing his or her appropriate task and, in Plato’s view, guided by the wisdom of the philosopher rulers, so in the healthy person all parts of the soul must co-operate together under the guidance of reason. Just as the much more numerous third portion of the state always endangered its good working, so in the body uncontrolled desire had a damaging effect on reason and, in the end, its own well-being. In the Timaeus, a mythic account of reality, this tripartition is extended further by locating each part of the soul in a specific part of the body.15 The highest part of the soul is placed in the brain, the energetic part in the heart, and the lower, appetitive part in the belly, where can be found the liver, stomach and spleen. Plato does not make clear the detailed physiology of these lower organs, although he makes the liver the chief controller among them, just as his picture of the heart and its vessels is highly schematic. It was left to later scholars, Galen in particular, to correlate the tripartite soul with three largely independent bodily systems, the brain and nerves, the heart and arteries, and the liver and veins. Plato does not go this far, not least because a clear-cut distinction between the venous and arterial systems had not yet been drawn. Plato’s linkage of soul and body in the Timaeus also introduces a physicalist strain into his explanation of diseases of the soul. Simply by being located in the body, the immortal soul is hampered in its activity, and affected by both nature and nurture. Some psychic disorders are the result of bad upbringing, but others have a physical origin. Morbid humours, in particular bile and phlegm, send out vapours, which have a different effect depending on which part of the soul they reach. Madness (mania) and stupidity may both have their origin in changes in the body: alterations in the marrow, for instance, affect one’s perceptions of pleasure and pain. If this is so, the correction of these mental or psychic aberrations must involve treatment of the underlying physical condition. So from one’s earliest years one should receive a suitable

physical and mental training, with appropriate regimen and gymnastic exercises, in order to keep the physical body as healthy as the mind. Drugs are not recommended by Plato, except as a very last resort.16 The medical sections of the Timaeus, then, are far from lacking in interest. They show a non-medical man, Plato, utilising ideas that, as we know from both the Hippocratic Corpus and Anonymus Londinensis, were at the forefront of medical debate at the time in order to write his own account of the creation of the human body and to explain some of its mental or psychic defects. His subsequent influence brought these ideas to a wide audience, and they, in turn, were developed by commentators who might themselves introduce further medical arguments and evidence.17 Galen, as we shall see, was convinced that Plato had studied medicine with Hippocrates, and that Plato’s notions of the body could reveal much about the teaching of Hippocrates that was otherwise unclear from the Hippocratic Corpus.18 But, even if Galen’s belief in Plato the medical student is largely his own invention, other more sober commentators brought their own medical information to bear on philosophical problems.19 The celebrated (and disputed) passage about Alcmaeon’s introduction of anatomy, for example, is preserved today only because a late Latin commentator on the Timaeus, Chalcidius, used it to explain further what Plato was doing in his account of sight (at 67d-e).20 Unlike modern medical historians, Chalcidius was not concerned with what Alcmaeon had actually done (even if he could have found out), but only with the relevance of his theories to those of Plato. Plato’s pupil, Aristotle, the son of a court physician to the King of Macedon and an Asclepiad on both his mother’s and his father’s side, continued this interest in matters medical, although in a very different way from his master.21 He posited a continuum between doctors and natural philosophers: most natural philosophers in their account of the world had also to consider medicine, while the more thoughtful physicians grounded their medical theories upon the principles of natural philosophy. He himself attacked problems that might be called medical, particularly in relation to psychology, while, at the same time, drawing on medical data to exemplify and to support his position in debates with philosophers.22 He himself brought into harmony both the medical theories about opposites and the philosopher’s ideas about elements, and, in particular, the four basic elements, the hot, cold, wet and dry. In the Aristotelian universe medical theory, and most notably the fourelement theory of The Nature of Man, could find a secure home. The human body was built up out of the four elements, and its natural processes could be explained by Aristotle’s physical principles. The inner heat of an animal was, so to speak, an ‘internal fire’, and the main function of air or pneuma was to cool this heat and prevent it from getting out of control and damaging the organism. The brain, Aristotle believed, acted as a refrigerator to cool down the fiery heart, the seat of the single and unified organic soul.23 Aristotle, like Plato, established his own school, the Lyceum, in Athens, where he and his pupils embarked on a wide-ranging and ambitious

programme of empirical investigation. They collected and studied information on the whole world of nature and of human endeavour, from records of the constitutions of the various city-states and the opinions of doctors, to botany and mineralogy.24 This enterprise was backed by influential patrons. Aristotle had worked first at the small court of Assos (now W. Turkey), before becoming the tutor of the future Alexander the Great. The support of Alexander allowed Aristotle to exploit immediately the conquests made by his army as it traversed the Persian Empire as far as the mountains of Afghanistan and the plains of the Punjab between 334 and Alexander’s death in 323. The conquering troops were accompanied on their marches by scholars who kept records, measured distances and sent back to Aristotle in Athens specimens of the new minerals and plants that they found.25 Aristotle himself was passionately interested from his earliest years in what we would now term biology and zoology. He collected information on a wide range of animals, birds and fishes, even going so far as to perform systematic dissections on at least fifty different kinds of animal. He was as well informed about the development of the chick in the egg as about the habits of bees or the feet of the ostrich.26 His credo, as set out in his treatise The Parts of Animals, is a stirring call to investigate the natural world, ‘for every realm of nature has something marvellous about it’.27 He was prepared to acknowledge that looking at the constituent parts of bodies, blood, flesh, bone, vessels and so on, might easily appear disgusting and shameful, but that was only if one concentrated on the individual building blocks and not on the whole house, or form. If one did that, then one would see the beauty of the craftsmanship of nature, and one would derive great pleasure from being able to discover and recognise the true causes of things. In particular, one would quickly become aware that ‘in the works of nature, purpose, not chance, predominates’. Aristotle is here committed to the study of biology in accordance with his general philosophical principles, and the primary object of this study is not the individual detail of any part but their composition as a whole. In particular, the abundance of his information served to confirm one of Plato’s central tenets in the Timaeus, teleology – or, in Longrigg’s words, the doctrine of internal finality within nature – although Aristotle did not commit himself to his master’s belief in a comprehensive and conscious design on the part of nature.28 One studied the natural world, not only for what it was itself, but in order to gain insights from more accessible, albeit also transitory, material than was possible from the contemplation solely of the precious and divine heavenly bodies. That knowledge was more pleasing, but inevitably only partial; it needed to be supplemented by the empirical study of the things on earth. These included animals, living beings, of which humans were only one. Aristotle’s project aimed at encompassing all of them, ‘noble and ignoble alike’. There is thus no specific anthropology in his writings, no treatise devoted to an examination of the human body by itself. This would have

been an extremely difficult task, as he himself admits, for ‘the inner parts of the body are unknown, especially those of man’, but also an unnecessary one, if the requisite information that contributed to the overall understanding of nature could be obtained by other means. Analogy with other animals provided that means, ‘looking at those animals which have parts similar to those of humans’.29 Since at this time there were strong taboos in Greece against interfering with a human body, let alone dissecting it, human anatomy was out of the question. That of animals, birds and fishes was not, and Aristotle refers often to his own investigations (and to those of others, including, almost certainly, Diocles) into their organisation, structure and, above all, functions.30 His results are far more detailed and wide-ranging than those of his predecessors, although at times his account is not easy to follow. His description of the vascular system, for example, both includes new observations and omits (or misunderstands) much that we might consider obvious. His description of the heart as having three chambers continues to divide modern interpreters into those who believe that Aristotle erred in what he saw when he carried out his dissection and those who argue that it is Aristotle’s starting point for the description that differs from ours, not his observation.31 His notions that the hearts of large animals, such as horses, had a bone within and that the number of chambers in the heart was related to size are a nice blend of fact and misunderstanding.32 But there are times when Aristotle got things wrong beyond any dispute. Because he failed to find any blood vessel extending to the brain, he concluded that the brain in all animals was bloodless.33 His belief that females have fewer teeth than males, and fewer cranial sutures, may be based on incomplete observations, but was also influenced by his underlying conception of woman as an inferior and somehow incomplete version of man.34 But his mistakes are relatively few in comparison with his accurate descriptions of phenomena in the living world, and do not detract from the example he set to others (and to their patrons) of the value of such empirical research. He raised big questions about the whole process of life, from movement and sensation to ageing and sleep, although almost all that he himself wrote specifically on medicine has disappeared.35 His influence, which was substantial, took many different forms. Through his teaching of logic at the Lyceum, Aristotle created what might be described as the scaffolding for future intellectual debate, emphasising correct logical argument and the importance of a proper definition of terms in any exposition of medical or scientific material. In turn, by setting medicine and the human body within the wider system of the cosmos he allowed a dialogue about the causes of the natural processes within the body to be conducted at a deeper level of explanation. We can trace a whole series of debates with Aristotle over the interpretation of medical phenomena from his immediate pupils through to Galen, whose own influential systematising depends on a basically Aristotelian epistemology and on a combination of data drawn from the Hippocratic Corpus and Plato and inserted into a

world of Aristotelian physics.36 Aristotle’s successor as head of the Lyceum, Theophrastus (c.371-287), not only included many medicinal plants in his Enquiry into Plants, but also wrote short tracts on such obviously medical topics as sweating, fatigue and giddiness. Other Peripatetics such as Strato of Lampsacus investigated questions that were to have repercussions for later physicians, while, conversely, medical notions about the brain came to play a major role in philosophical discussions on the soul.37