Galeno

Galen (ad 129–c.210)

Galen was the most influential doctor of late Greco-Roman antiquity. But he was also a notable philosopher, who desired to effect a synthesis of what was best in the work of his predecessors, not only in medicine but also in logic, epistemology, philosophical psychology and the philosophy of science and explanation. In logic he made use of both Aristotelian and Stoic material, but supplemented them with his own treatment of relational logic. His epistemology, while resolutely anti-sceptical on the grounds that nature could not have furnished us with systematically delusive sense-organs, was none the less sober and cautious: some philosophers’ questions are simply unanswerable. He attacked the Stoics’ unitary psychology, establishing by means of detailed experiments that the brain was the source of voluntary action. Finally, drawing on the philosophical and medical tradition, he crafted a theory of cause and explanation sophisticated enough to rebut the sceptical challenges to such notions, and rich enough to enable him to construct a comprehensive physiology and pathology on its basis.

1 Life and work

Galen is best known to history as a doctor, the systematizer of a Hippocratism (see Hippocratic medicine) which became the foundation of medicine for more than 1,500 years. But he was also a considerable philosopher in his own right, writing extensively on logic and language, and scattering philosophical remarks, arguments and controversies throughout his vast medical oeuvre. And this is no mere accidental collocation of interests, to be explained by the fact that he trained first in philosophy before turning to medicine. He wrote a short pamphlet That the Best Doctor is Also a Philosopher, which survives, stressing the intimate connections between the two disciplines, and never tired of pointing out the errors made by his medical colleagues caused by their insufficient attention to logical detail and their ethical shortcomings.

Galen was born into a well-to-do family in Greek Asia Minor, and received an extensive liberal education, learning philosophy from leading Platonists and Peripatetics, as well as Stoic logic. He had little time for atomism in any of its forms (see Atomism, ancient), and is scathing about the inability of the atomists, and doctors influenced by them, to give satisfying explanations of complex phenomena in purely material terms without recourse to teleological explanation. For Galen, teleology was an essential part of any rationally acceptable explanation of the world and its contents.

Galen travelled widely in pursuit of his education, absorbing both Empiricist and Rationalist views (see Hellenistic medical epistemology), which conspired to nurture his distinctively eclectic views in methodology, as well as a syncretism in philosophical outlook typical of the times (although original enough in its elaboration). He moved to Rome in 162, making (on his own account, in On Prognosis) an immediate impact upon the cultural and aristocratic elite for his competence as a doctor and for the soundness of his logical reasoning.

He wrote at a furious pace, dictating to relays of scribes, and his output of treatises medical and philosophical, in the form of original monographs or of commentaries on the masters was correspondingly enormous (see §2 below). Some of this oeuvre was destroyed by fire in his own lifetime, and much else has been lost since. But a great deal survives in Greek (Kühn’s monumental edition runs to about 10,000 pages of text), and much else in other languages, notably Arabic, Latin and Hebrew, a fact ensured by his early acceptance in the Islamic world as the great repository of medical wisdom. His influence on the subsequent history of medicine was enormous, his views in physiology and anatomy not being superseded until the sixteenth century, his medicine itself surviving even longer.

2 Galen’s intellectual inheritance

Galen’s chief sources of inspiration were Hippocrates and Plato, his On the Doctrines of Hippocrates and Plato being a typically syncretistic attempt to demonstrate their basic agreement on all important issues. His theory of disease is fundamentally Hippocratic in conception: an illness consists in the impediment to or destruction of one of the crucial functions of the body, while treatment involves restoring that function to its proper state. These impediments can take the form of imbalances in the fundamental four humours, blood, phlegm, and yellow and black bile, which regulate the body; and each of the four humours is itself associated with one pair of the four basic qualities, hot, cold, wet and dry, which may by distempered either individually, or in their humoral pairs. Furthermore, there are four types of disease of the organic parts, plus a general category he terms ‘loss of cohesion’ (this scheme forms the basis of On the Therapeutic Method). However, for Galen, Hippocrates was important not so much as a medical gospel, but rather for having exemplified a methodology of investigation, theorizing, and testing, which, if competently pursued, would in time reveal the whole of medical truth.

Galen’s greatest philosophical debt to Plato is his adoption and elaboration of the type of creationist natural teleology sketched in the latter’s Timaeus (see Plato §16; Teleology). For Galen, this time in agreement with the Stoics (see Stoicism §5), the idea that the world, in all its structural regularity, might be a spontaneous efflorescence of blind mechanical forces was simply anathema: no mechanical theory could possibly account for the complexity and organization of the world and its inhabitants. Moreover, the artifice of such a world demands an actual Creator: Aristotelian purely immanentist teleology is equally unsatisfactory. Galen calls his own great teleological account of biological structure and function, On the Function of the Parts, a ’hymn to Nature’ and the Creator. Those (such as Erasistratus; see Hellenistic medical epistemology), who have dared to say that Nature on occasion does something in vain have simply failed to appreciate the subtlety and complexity of her works, which are only apparent to the skilled and conscientious investigator.

Galen also seeks in On the Doctrines of Hippocrates and Plato to ground the Platonic hypothesis of a tripartite soul, with reason in the brain, emotion in the heart and desire in the liver, upon detailed anatomical investigation and experiment. He subjects the unitary psychology of the Stoics (see Stoicism §19) to a withering attack, accusing them of logical incompetence as well as blindness to the evidence. Yet Galen was equally powerfully influenced by the Peripatetic tradition in natural science: while the underlying pattern to his teleology is Platonic, the great model for his practical work in the investigation of function is Aristotle’s biology. And he admired Aristotle’s logic, sometimes troubling to cast his arguments in syllogistic form (but see §4 below).

3 Theory of causation

Equally, Galen happily adopts the basic model of Aristotle’s four causes (Physics II 3) and deploys it in his own analysis (see Aristotle §9). There is ample room for the final cause in nature given his commitment to teleology; efficient causes clearly have a role in explaining how things come to be what they are; while a just appreciation of the importance of the material cause will help to evade some of the stronger sceptical attacks (notably again those of Erasistratus) upon the coherence of the notion of causation in the first place. The reason why different things respond differently to the same influences (the prime empirical weapon in the sceptical armoury) is that they are differently constituted, and so differently susceptible (a view perfectly consistent with Hippocratism: the different constitutions, at least in the case of animals, will be humoral in structure).

Yet Galen’s use of Aristotle is selective and creative. He has very little use for the formal cause (or indeed for Platonic hypostasized Forms) as such, although he is perfectly well aware of the importance of form for function. He simply does not regard it as a properly separate explanatory category; instead he adopts the Middle Platonist category of the instrumental cause.

Equally, his treatment of efficient causes is unorthodox, since he happily embraces the Stoic (or at least Stoic-influenced) treatment of causal agency as involving categorially distinct stages. There are antecedent causes, external influences brought to bear on objects (or physical systems), which may, if they are suitably disposed, trigger in them a sequence of events leading to the establishment of some further condition (for example, disease). But antecedent causes are not on their own sufficient for their effects; they operate only on patients in a suitable condition, and even then their progress may, if caught early enough, be arrested. For they set in motion processes within the organism, a sequence of preceding causes, which then culminate (unless appropriate action has been taken) in a set of conditions both necessary and sufficient for the disease in question, as well as being contemporary with it: the so-called ’containing’, or sustaining, cause.

Thus Galen’s detailed account of causal efficiency involves a wholly un-Aristotelian concentration on the sequential nature of causation as a temporal phenomenon; and, in addition to being of sufficient complexity and sophistication to defuse sceptical objections, it allows him to build up a detailed theoretical account of the structure of human pathology.

4 Reason and experience

Galen’s commitment to theory places him in the Rationalist camp (see Hellenistic medical epistemology); but he insisted with the Empiricists upon the importance of testing, and sought to effect a reconciliation: theory without experience was empty, but experience without theory, blind. He emphasizes the importance of practical engagement in physiology and medicine; of regular, repeated observation and experiment; but he also believes that such observation is hamstrung unless it can be placed within its appropriate theoretical context. Students of medicine must make repeated dissections and vivisections in order to learn the structure and arrangement of things in the body; but they must also learn to sytematize those observations by attending to logic, and to understand them in nature’s teleological light.

The basic theoretical categories he adopts, the four qualities, while not directly equivalent to their phenomenal counterparts, are still susceptible of empirical appreciation. Chilled white wine is, surface indications notwithstanding, hot and dry, since its effect is to heat and desiccate. Empirical testing, the main tool in the Empiricist context of discovery, is equally essential for Galen, but rather in the context of justification. The theories elaborated by reason on the basis of observation must themselves answer at the tribunal of experience.

Galen never abandons his belief (stated in the opening books of On the Therapeutic Method) that medicine can be made into an Aristotelian demonstrative science, where necessarily true theorems flow ineluctably from indubitable axioms, which include definitions stating the essence of things as well as fundamental logical and metaphysical principles, such as the law of the excluded middle and the principle of causality. Yet for such a science to be of practical use, it must be applicable to contingent circumstances, and pass stiff empirical tests. Moreover, given the diversity of circumstances, practical medicine will never be infallible; but if it is probabilistic, it is so not because of any intrinsic uncertainty in nature itself, but only because of our own inabilities to see clearly or accurately enough into it.

Galen insisted on the importance of training in logic, for systematizing empirical evidence and exposing others’ fallacies. He made use of Stoic as well as Aristotelian argument schemata (although not uncritically: he rejects the Stoic third ’indemonstrable’ (see Stoicism §11) as incapable of delivering necessary conclusions); and he saw more clearly than either school that neither system could handle relations properly, a deficiency he sought, albeit rather naïvely, to remedy with an account of ‘relational syllogisms’.

Galen was not overly sanguine about knowledge; indeed he held that many of the disputes of the theoretical philosophers and cosmologists, over the nature of the soul or the existence of an extra-mundane void, were simply undecidable, since reason alone cannot decide them and neither is there any relevant experience to be won regarding them. But where they can operate, the sense-organs are ’natural criteria’; and nature does nothing in vain. Thus animals must naturally be able to assimilate perceptible form, and no inductive problem of the sort which plagues empiricist accounts of concept-formation arises. Equally, scepticism is refuted by teleology. It is by analysis of these naturally arising conceptions that we may, if we are able and conscientious enough, arrive at the real, definitional principles of things upon which all genuine, scientific knowledge is based.