Pneuma

Summary

Pneuma — Greek for “breath,” “air,” or “spirit” — was one of the most durable concepts in Western medicine. Originating in pre-Socratic cosmology as the idea that air is the fundamental substance of reality, it entered medicine through Hippocratic and Aristotelian physiology as a refined vital substance responsible for sensation, motion, and the maintenance of life. In Galen’s system, pneuma became a tripartite framework: natural spirit produced in the liver, vital spirit refined in the heart, and psychic spirit elaborated in the brain. This schema, systematized further by Arabic commentators, structured physiological thinking from the second century CE until William Harvey’s demonstration of the circulation of the blood in 1628 rendered it untenable. Its later echoes persisted in Renaissance doctrines of spiritus and early modern vitalist thought until new chemical and mechanical frameworks finally displaced it.

Pre-Socratic Origins: Air as Cosmic Principle

The concept of pneuma traces to the Ionian natural philosophers of the sixth and fifth centuries BCE. Anaximenes of Miletus proposed that all substances are forms of air at different densities, creating what Partington describes as a “ladder of being” from fire through stone via condensation and rarefaction.(Partington, J.R., 1970) This was not merely a physical claim. Osler notes that Anaximenes’ doctrine that air is the primary principle gave rise directly to the medical concept of pneuma — “the breath of life or psychic force which animates the body and leaves it at death” — crystallized in the fragment attributed to him: “Our soul being air, holds us together.”(William Osler, 1921)

Diogenes of Apollonia, working in the later fifth century, pushed this monistic air-theory further into physiology. Two Hippocratic treatises — Breaths and Sacred Disease — are plainly influenced by Diogenes, as Longrigg demonstrates, despite the fact that another Hippocratic text, Nature of Man, specifically attacks monistic hypotheses and displays hostility toward Diogenes in particular.(Longrigg, 1998) The paradox reveals how deeply pneuma-thinking had penetrated Hippocratic medicine even as other authors in the same tradition tried to expel it.

The Sicilian medical tradition, rooted in Empedocles’ four-element theory, contributed a second strand. Empedocles taught that the blood is the seat of innate heat and the heart the centre of the vascular system, and Singer notes that “his teaching led to a belief in the heart as the centre of the vascular system, and the chief organ of the pneuma which was distributed by blood-vessels.”(Singer, 1957) The most influential doctrines of Sicilian medicine — innate heat as the underlying agent of physiological processes, respiration as a cooling mechanism for that heat, blood as the vehicle of nutrition manufactured in the liver — can be traced back to Empedocles, as Longrigg argues.(Longrigg, 1998) Diogenes of Apollonia then modified Empedocles’ account of semen, holding that it is blood aerated into foam by innate heat and pneuma, a view later adopted by Aristotle, the Stoics, and Galen.(Longrigg, 1998)

Philistion of Locri, adapting Empedocles’ four-element theory into a systematic medical doctrine, explicitly tied pneuma to health: “When the whole body breathes well and the breath passes through without hindrance, health ensues.”(Longrigg, 1998) This is one of the earliest formulations linking the free passage of breath through the body to the definition of health itself.

Longrigg summarizes the combined legacy: Empedocles and Diogenes of Apollonia, though philosophically opposed as pluralist and monist, “exercised the greatest influence on contemporary and subsequent Greek medicine, introducing doctrines of pneuma, innate heat, and blood as the agent of nutrition.”(Longrigg, 1993)

Hippocratic and Fourth-Century Development

Within the Hippocratic Corpus itself, pneuma appears in several guises. The Anonymus Londinensis papyrus attributes to Hippocrates a theory that diseases are caused by physai (gases or breaths) arising from undigested food residues, a claim some scholars identify with the treatise Breaths.(Longrigg, 1998) The treatise Sacred Disease uses pneuma as part of a naturalistic explanation for epilepsy, arguing that the brain is the organ of intelligence and that blockages of air or phlegm in the vascular pathways to the brain cause seizures. None of these Hippocratic texts present a single unified pneuma doctrine; the Corpus remained pluralistic, with different authors offering humoral, elemental, and pneumatic explanations for the same phenomena.(Longrigg, 1998)

The fourth-century physicians who followed — the group Galen later called the “Dogmatists” or “Logical Physicians” — gave pneuma its first systematic physiological role. Diocles of Carystus accepted four humours but paid particular attention to pneuma as “refined air” that spread through the body’s vessels to effect voluntary motion.(Nutton, 2023) Partington confirms that Diocles “taught that pneuma is the natural heat of the body (emphyton thermon) and that digestion is a kind of putrefaction.”(Partington, J.R., 1970) According to Rocca, Diocles appears to have been the first to use the expression “psychic pneuma” (psychikon pneuma), locating the hegemonikon in the heart; Galen also credited Diocles with writing the first anatomical manual.(Rocca, 2003) Diocles’ pneuma pathology was specific: if the passage of pneuma around the body was blocked by congealed phlegm within the aorta, the result was epilepsy and apoplexy; when the obstruction affected the heart — which Diocles identified as the source of “psychic pneuma” — it caused melancholy.(Nutton, 2023) As Longrigg notes, both Diocles and Praxagoras explained epilepsy as blockage of psychic pneuma in the aortic region by phlegmatic humours, demonstrating continuity with the naturalistic tradition of the Hippocratic Sacred Disease.(Longrigg, 1998)

Praxagoras of Cos, a generation after Diocles, made the anatomical move that would shape pneuma theory for centuries. He distinguished veins from arteries for the first time and made the further assumption that “veins carried blood, the arteries only pneuma.”(Nutton, 2023) He was also the first to see in the pulse a valuable diagnostic aid, taking the movements of the arteries as an index of changes elsewhere in the body.(Nutton, 2023) Praxagoras thus established the working model — arteries as pneuma-channels, pulse as diagnostic window — that the Alexandrians inherited and Galen would later transform.

Van der Eijk reconstructs Diocles’ use of psychic pneuma as part of a more elaborate picture in which the heart, the brain, and pneuma all play distinct roles. On Diocles’ theory the heart is “the real seat of the mind” while the brain has a pivotal role in sense perception, and “the so-called ‘psychic pneuma’, a delicate substance … is responsible for transmitting sensory and motor signals” between them.(van der Eijk, Philip J., 2005) The pathological consequences of this scheme are visible in Caelius Aurelianus’ summary of how Diocles and Praxagoras explained epilepsy: phlegmatic humours form within the thick artery, “form bubbles and obstruct the passage of the psychic breath coming from the heart, and in this way this [the breath] causes the body to be agitated and seized by spasms,” with Diocles agreeing that the obstruction occurs in the same place and works in much the same way as Praxagoras described.(van der Eijk, Philip J., 2005) Pneuma here is not just the carrier of consciousness but the precise variable whose blockage produces convulsion.

Van der Eijk also warns against reading the standard tripartite doxography (encephalocentric, cardiocentric, haematocentric) back into fifth- and fourth-century texts as though it captures their actual disagreements. “Strictly speaking, only the authors of On the Sacred Disease and On the Heart express an opinion on the location of what they consider the highest psychic faculty”; most other authors mentioned by later doxographers “appear to regard psychic activities mainly as processes … based on the interaction between a number of anatomical and physiological factors,” with pneuma as one of those factors rather than as a substance bound to a single anatomical seat.(van der Eijk, Philip J., 2005) The schema that maps each early thinker onto a single seat of the hēgemonikon is a later overlay; the fifth- and fourth-century texts often work with distributed processes in which pneuma is one variable among several.

In Aristotelian biology, pneuma took on yet another dimension. Aristotle did not use the term in quite the same way as the medical writers. He posited an “innate pneuma” (symphyton pneuma) in semen as the vehicle of soul’s generative faculties, distinct from ordinary air. The Peripatetic text De Spiritu — attributed to either Theophrastus or Strato — goes further, asserting that pneuma is distributed from the heart as the organ of sensation and discussing its movement through sinews and nerves.(Partington, J.R., 1970) This work stands as an important bridge between Aristotelian biology and the later Pneumatist medical sect. Van der Eijk presses a refinement of how Aristotle himself should be classified: the heart for Aristotle is the archē of bodily heat and the seat of the central sense organ, while the brain has no cognitive faculty and serves only to cool the heart’s heat. But because Aristotle’s highest faculty (nous) is not located anywhere in the body, “it is, strictly speaking, not correct to attribute a cardiocentric view on the mind to Aristotle, as has frequently been done both in antiquity and in modern literature.”(van der Eijk, Philip J., 2005)

Alexandrian Physiology: Erasistratus and the Pneumatic Body

The Alexandrian physicians of the third century BCE carried pneuma theory into new anatomical territory. Erasistratus, younger contemporary of Herophilus, believed — following Praxagoras — that arteries normally contained only pneuma, not blood. When an artery was severed, the escaping pneuma created a vacuum drawing blood from adjacent veins through fine capillaries (sunanastomoses), which he called the principle of pros to kenoumenon akolouthia (horror vacui).(Longrigg, 1998) Porter confirms that for Erasistratus, pneuma was taken in through the lungs, piped to the heart (which he compared to a blacksmith’s bellows), and then pumped out to fill the arteries.(Porter, 1997)

Singer notes that Erasistratus “recognized only two forms of spirit” within the animal body — the vital spirit in the arteries and the psychic spirit in the nerves — making him the immediate precursor but not the author of the three-pneuma schema later attributed to Galen.(Singer, 1957) Erasistratus’ system was genuinely physiological: the heart functioned as a double pump, and the valves maintained unidirectional flow. Yet the refusal to admit blood into the arteries meant that Galen later found him an irresistible target.

The Pneumatist Sect

In the first and second centuries CE, a distinct medical sect took pneuma as its organizing principle. The Pneumatists, founded by Athenaeus of Attaleia, placed great emphasis on pneuma as “the controlling factor in health and disease,” combining Stoic philosophy with Hippocratic dogmatic medicine.(Nutton, 2023) Elliott notes that Athenaeus taught the sect in Rome around AD 69, with the doctrine that the union of heat and moisture in pneuma maintains health, heat and dryness cause acute diseases, and cold and moisture cause chronic diseases.(James Sands Elliott, 1914)

Athenaeus held that the proper balance of hot and cold in pneuma constituted “almost a fifth element” as the principle producing growth and maintaining life, which he equated with the Hippocratic concept of innate heat.(Nutton, 2023) He also explored parallels between the microcosm of the body and the macrocosm of the universe, a Stoic theme that would persist throughout the pneuma tradition.

The reach of pneuma into traditions that were officially hostile to such hidden substances is a useful index of the concept’s grip on Greco-Roman medicine. The Methodists rejected hidden causes in principle, yet Caelius Aurelianus in Acute Affections and Chronic Affections repeatedly invokes pneuma in clinically specific ways: he describes how the motion of the heart can be “paralysed by the movement of the pneuma which, as a result of a slowness, is not present in sufficient measure, so that after making a beat it draws to itself from the rest of the body the pneuma that had previously been distributed.”(van der Eijk, Philip J., 2005) He also describes cases in which “physical strength simply dissolves without sweating and their natural vigour is destroyed because of an invisible dissolution, which the Greeks call adēlos diaphorēsis.”(van der Eijk, Philip J., 2005) Even a school whose epistemology forbade hidden entities found pneuma indispensable when the disease itself required reference to invisible processes.

The Pneumatist school produced notable clinicians. Archigenes of Apamea wrote extensively on pulse diagnosis, identifying eight different qualities with names like “double hammer,” “mouse-tail,” and “gazelle-like pulse.”(Nutton, 2023) Aretaeus of Cappadocia, often associated with the Pneumatists, explained asthma as “a cooling and moistening of the pneuma” and produced disease descriptions that Nutton calls the finest nosological studies surviving from antiquity.(Nutton, 2023) French confirms that by Galen’s time in Rome, the Pneumatists were one of four competing sects, alongside the Empiricists, Rationalists, and Methodists, and that Galen “used some doctrines that had found favour with the Pneumatists” even as he claimed independence from all sects.(French, 2003)

Galenic Pneuma: The Triple System

Galen of Pergamon (129—c. 216 CE) assembled the various strands of pneuma theory into the system that would dominate Western medicine for over a millennium. Singer in his Applebaum chapter describes the result: Galen “posited three types of pneuma distributed through different conduit systems: psychic pneuma through nerves from the brain, vital pneuma through arteries from the heart, and natural spirit through veins from the liver.”(Applebaum, 2023) Each pneuma corresponded to one of the three principal organs and its associated faculty. As Singer describes in his anatomy history, “these three pneumas — the natural spirit, the vital spirit, and the animal spirit — formed the basis of the physiological system till Harvey.”(Singer, 1957)

The anatomical substrate was equally specific. Galen described the body as three near-separate systems centred on liver (nutrition via veins), heart (vitality via arteries), and brain (sensation and movement via nerves), following Plato’s tripartite model against Aristotle and the Stoics.(Nutton, 2023) Singer in the Applebaum volume details how Galen synthesized Platonic and Stoic models into a distributed psychology: “the rational soul in the brain, the spirited (thymoeidic) soul in the heart, and the desiderative (appetitive) soul in the liver, each organ serving as both a physiological center and a seat of psychic function.”(Applebaum, 2023)

The mechanics of pneuma production were bound up with Galen’s cardiovascular anatomy. He believed that some venous blood passed through perforations in the interventricular septum of the heart to the left side, where it joined refined air coming from the lungs via the pulmonary vein — an error that persisted until Harvey.(Nutton, 2023) In the left ventricle, this mixture was elaborated into vital pneuma. Some vital pneuma then ascended to the brain, where it was further refined into psychic pneuma in a vascular structure called the rete mirabile — which Galen described in animals but which does not exist in humans.

Temkin’s detailed study of Galen’s pneumatology, however, reveals that the neat triadic schema conceals considerable ambiguity in Galen’s own writings. The psychic spirit (brain and nerves) and vital spirit (heart and arteries) are well-defined categories for Galen, but the “natural spirit” (liver and veins) is mentioned only tentatively and lacks a clear function. Temkin concludes that “the canonization of the three spirits came later” — meaning the systematic tripartite schema was produced by late Alexandrian commentators, not by Galen himself.(Temkin, 1977)

Galen’s treatment of vital pneuma was also internally inconsistent. In combating the Erasistrateans, who denied blood in arteries, Galen minimized the role of pneuma in arteries and argued that very little inspired air reaches the heart — “we need a quality rather than a substance from the air.” In other words, when fighting one adversary, he undermined his own doctrine as deployed against others.(Temkin, 1977)

Galenic Synthesis: Brain, Ventricles, and Psychic Pneuma

The Hegemonikon Debate

The deepest stakes of Galen’s pneuma theory lay in a dispute that predated him by centuries. Rocca’s monograph on Galen’s brain science establishes that by the second century CE there existed a broad informal consensus that some “governing principle” (hegemonikon) commanded the body’s activities from a single anatomical seat, but physicians and philosophers were divided between those who placed it in the brain (encephalocentrists) and those who placed it in the heart or its immediate vasculature (cardiocentrists).(Rocca, 2003) This encephalocentrist/cardiocentrist polemic was one of the central debates in ancient medicine and philosophy, with the location of the hegemonikon implying very different accounts of how pneuma and neural function were organized.(Rocca, 2003) The very term hegemonikon was a Stoic coinage, devised by Stoicism to denote the ruling part of the soul.(Rocca, 2003) The Stoics under Chrysippus located the hegemonikon in the heart; Aristotle had argued similarly on the grounds that the heart is the first organ to form, is centrally situated, and is the source of the blood vessels. Praxagoras of Cos added a structural claim: the arteries, when traced to their distal ends, become the nerves, making the heart the ultimate source of neural power.(Rocca, 2003) Galen had to answer this tradition directly to make any theory of psychic pneuma in the brain stick.

For Galen, the brain is the hegemonikon for two reasons: it is the source of origin (arche) of all the nerves, and it alone produces the conditions for sensation and voluntary motion, which are the defining activities of the rational soul. Psychic pneuma functions as what Galen calls the rational soul’s prôton organon — its “first instrument.”(Rocca, 2003) The distinction matters philosophically: the soul itself resides in the brain substance, not in the ventricular cavities; the ventricles house the soul’s primary instrument but not the soul as such.(Rocca, 2003) Galen assembled Hippocrates and Plato as supporting authorities for the brain’s hegemonic status, while he drew on Aristotle for his methodology of dissection and experimentation.(Rocca, 2003)

The Three-Stage Elaboration Model

Rocca’s most precise contribution to understanding Galen’s pneumatic theory is his reconstruction of a three-stage elaboration process described in De usu partium. Outside air draws its first elaboration in the flesh of the lungs, producing a pneuma-like substrate. This substrate undergoes second elaboration in the heart and arteries, particularly in the retiform plexus (diktuoeidês plêgma, “net-like web”) at the base of the brain. A final elaboration in the ventricles of the brain — completed by the choroid plexuses — converts the substance into fully formed psychic pneuma.(Rocca, 2003) The three organ-stages map onto the three pneumas: lungs prepare the material; heart and retiform plexus produce vital pneuma; brain ventricles yield psychic pneuma.

This sequential model was not a simple pipeline. Galen employed the Aristotelian concept of coction (pepsis, analogous to cooking or boiling) to describe each stage: every elaborative step involved a qualitative transformation requiring time, specific organ faculties, and structural conditions suited to the work.(Rocca, 2003) Each organ possesses a distinct faculty (dynamis) tied to its unique substance (ousia), and for Galen the structure of an organ determines its function — the retiform plexus elaborates psychic pneuma for the same reason the liver elaborates blood and the stomach digests food.(Rocca, 2003)

The Retiform Plexus: Anatomy and Anatomical Error

The retiform plexus was, according to Rocca, the centrepiece of Galen’s pneumatic physiology of the brain, and simultaneously its most consequential anatomical error. Galen described it as a multilayered arterial network derived from the internal carotid arteries and located in the space between the dura mater and the base of the skull, where the carotid arteries divide into many fine branches before reconverging to enter the brain.(Rocca, 2003) He called it both a “complex labyrinth” (poikilos labyrinthos) and — the phrase that would echo through fifteen centuries of anatomy — “the most marvellous” (megiston thauma) of the structures near the pituitary gland.(Rocca, 2003) The elaborative logic was teleological: greater anatomical complexity produces finer elaboration, and the retiform plexus is more intricately coiled than any comparable structure because psychic pneuma requires more precise elaboration than any other bodily product.(Rocca, 2003)

To explain how this elaboration works, Galen reached for an analogy from reproductive physiology. The testicular vessels form a convoluted “ivy-like plexus” through which blood is elaborated into semen; one can observe blood changing colour along the course of those vessels. Rocca notes the epistemological problem: Galen then argues that the retiform plexus must work analogously, even though no comparable observation of colour change within the retiform plexus is available.(Rocca, 2003) His dissective skill is, as Rocca puts it, “suborned to a necessarily speculative physiological need.”

The fundamental problem was anatomical. The retiform plexus is absent in humans and great apes; it is present in ungulates — ox, goat, pig, sheep — and Galen dissected it in these animals. Rocca argues that Galen, and probably Herophilus before him, erroneously extrapolated from animal dissection to human cranial anatomy.(Rocca, 2003) The structure was, as later anatomists would recognise, what one modern scholar has called a “fascinating mythological organ.” Berengario da Carpi, in his 1521 Commentary on Mondino, was the first to register explicit doubt, reporting that he had dissected more than a hundred human heads without finding the retiform plexus as Galen described; he concluded that “Galen has imagined the rete mirabile and he never saw it.”(Rocca, 2003) Vesalius confirmed the denial definitively in De Corporis Humani Fabrica (1543), having observed it himself only in ungulates.(Rocca, 2003) Yet even after Vesalius’s formal refutation, the physiological need for a pneuma-elaborating vascular structure persisted: Vesalius himself replaced the rete mirabile with the cerebral arteries; other Renaissance anatomists reassigned its function to the choroid plexus.(Rocca, 2003)

The Choroid Plexus and Ventricular Elaboration

The choroid plexuses (chorioeidê plêgmata) were named by the circle around Herophilus after the foetal chorion membrane, which they physically resemble. Herophilus was the first to describe them as “choroid-like knots” — a plexus of veins and arteries joined by thin membranes within the ventricular cavities.(Rocca, 2003) Galen accepted this description, noting that the choroid plexuses are supplied by continuations of the internal carotid arteries (which also feed the retiform plexus) and by veins from the dural venous sinuses, with the pineal body serving as a vascular support gland for the venous supply.

In De usu partium, Galen states that the final elaboration of psychic pneuma occurs within the ventricles, but in De placitis Hippocratis et Platonis he qualifies this claim as only “reasonable” (eulogon), not demonstrated.(Rocca, 2003) The choroid plexus receives less careful physiological treatment from Galen than the retiform plexus; his own summary in De placitis is that the veins of the choroid contribute to pneuma production only “in a small way,” while “the major and chief source of production is supplied from the arteries in the retiform plexus at the base of the brain.”(Rocca, 2003) Rocca identifies this hedged language as characteristic of Galen’s approach to brain physiology: where demonstration runs out, plausibility takes over.

Ventricular Experiments and the Harm Gradient

Galen’s empirical case for ventricular function rested on vivisection. The ventricles were the locus of psychic pneuma, which Galen described as the rational soul’s prôton organon — its “first instrument” — mediating sensation and voluntary motion from within the ventricular cavities rather than from the brain substance itself.(Rocca, 2003) When he exposed the brain of a living animal and incised or compressed each ventricle in sequence, he found a consistent gradient of effect: incision of either anterior (lateral) ventricle caused the least harm; the middle (third) ventricle produced intermediate effects; opening the posterior (fourth) ventricle caused the greatest loss of sensation and voluntary motion.(Rocca, 2003) The reversibility of some of these effects was important to his interpretation: if the wound sealed and the pneuma supply renewed, function could return, which Galen took as evidence that it was pneuma loss — not structural tissue damage — that produced the neurological deficits.(Rocca, 2003)

Galen also observed that the brain as a whole rises and sinks slightly in vivisected animals with a rhythm resembling arterial pulsation, a movement he interpreted as the mechanism by which psychic pneuma is actively distributed from the ventricles into the nerves.(Rocca, 2003) In De usu partium, he stated that the anterior ventricles perform actions of inspiration and expiration, drawing in and expelling matter analogously to the lungs — a “brain respiration” that connected his ventricular physiology to the broader pneumatic scheme.(Rocca, 2003)

An important qualification runs through all of this. Rocca draws attention to Galen’s own phrasing: pneuma is chrêsimos (useful) for sensation and voluntary motion, but not anankaios (essential or necessary). By stopping short of claiming pneuma is strictly indispensable, Galen signals awareness that his ventricular experiments cannot provide a complete explanation for brain function.(Rocca, 2003)

Carotid Ligation and Its Contradictions

To investigate the source of psychic pneuma, Galen used carotid ligation — his declared “best as well as the clearest method of deciding the source of the body’s activities.” After ligating both carotid arteries in experimental animals, he found the animals continued to breathe, move, and remain active through the day and into the night, a result he called atopôtaton — “highly unusual.”(Rocca, 2003) If the retiform plexus were the sole site of psychic pneuma elaboration, cutting off the carotid supply should have been immediately catastrophic. It was not.

Galen offered two different accounts of why the animal survived, and Rocca identifies an irreducible tension between them. In De usu respirationis, Galen concluded that the brain does not ultimately need pneuma from the heart and that psychic pneuma is nourished primarily by breathing in through the nostrils: outside air enters the anterior ventricles directly via the olfactory tracts, providing a route to psychic pneuma independent of the cardiac arterial system.(Rocca, 2003) This made Galen an ally of what he called the “school of Hippocrates” against the Erasistrateans, who held that all pneuma derives from the heart.(Rocca, 2003) In De usu pulsuum, by contrast, Galen argued that the retiform plexus acts as a reservoir of psychic pneuma sufficient to sustain the animal “for a long while” — especially at rest, when it is not expending pneuma in voluntary activity.(Rocca, 2003)

These two accounts cannot be fully reconciled. In one text the retiform plexus is primary; in the other, the olfactory air-source is primary. Rocca’s chapter-by-chapter analysis makes the divergence explicit: De usu pulsuum treats psychic pneuma as if it is entirely produced within the retiform plexus, while De usu respirationis focuses on formulating a role for outside air entering the brain.(Rocca, 2003) Rocca concludes that the tension was inherent to Galen’s choice of pneuma as his physiological agent, and that “his physiology demands something different from the retiform plexus and the choroid plexus depending on which text is consulted.”(Rocca, 2003) Galen never produced a synthesis that integrates both vascular structures into a single unified scheme.

Downstream Consequences: Cell Theory

Galen himself did not assign imagination, reason, or memory to specific ventricles: the rational soul’s activities encompassed all three, but none were localised to particular cavities.(Rocca, 2003) Rocca notes that placing psychic pneuma within the ventricular cavities was itself a strategic choice: by locating his chosen effector agent there, Galen could demonstrate brain hegemony over sensation and voluntary motion directly through ventricular experiments, making vivisection the instrument of proof for both pneuma physiology and encephalocentric hegemony simultaneously.(Rocca, 2003) What he left was what Rocca calls “plasticity” — a ventricular physiology open enough to support later speculative interpretation. Post-Galenic commentators collapsed his distinction between the physiology of the ventricles and the activities of the rational soul, and the result was the formal medieval doctrine of “cell theory.” As Rocca documents, Nemesius of Emesa (ca. 400 CE) fixed imagination (phantastikon) in the anterior ventricles, intelligence (dianoêtikon) in the middle ventricle, and memory (mnêmoneutikon) in the posterior ventricle — a framework that persisted through the medieval encyclopaedists into the Renaissance.(Rocca, 2003)(Rocca, 2003) This downstream development was possible because Galen’s ventricular physiology, precisely because it left so much unspecified, “afforded considerable scope for speculative interpretation” by later medical, philosophical, and theological commentators.(Rocca, 2003)

Scholastic Transmission and the Three-Spirit System

Whatever Galen’s own ambiguities, his successors resolved them into a fixed schema. The triadic system of psychic, vital, and natural spirits as presented in the Isagoge of Joannitius (Hunayn ibn Ishaq) represents what Temkin calls “a scholastic simplification of Galen’s ambiguous and inconsistent discussions — an example of how Alexandrian and Syro-Arabic heirs systematized what Galen left labile.”(Temkin, 1977) The Isagoge “flatly count[s] three spirits: natural, vital, and psychic,” where Galen had been cautious about the existence of a vital pneuma and very sceptical about a natural one.(Temkin, 1973)

In Galenico-Islamic humoral theory, the human body formally consisted of organs (solid), humours, and “spirits or pneumata (arvah).”(Jackson (ed.), 2011) The three-spirit doctrine became a standard feature of Islamic medical compendia, including Avicenna’s Canon of Medicine, and from there passed into the Latin medical curriculum through the Articella and its associated texts. The framework was accepted as straightforward Galenic physiology, though — as Temkin emphasizes — it was actually a product of reception rather than of Galen’s own settled convictions.

Ibn al-Nafis in the thirteenth century challenged one element of this pneumatic physiology. He denied the existence of pores in the cardiac septum and correctly asserted that blood passed from the right to the left ventricle only through the lungs.(Pormann, 2007) This was significant because the septum-pore theory was the mechanism by which Galenic pneuma-production supposedly worked: venous blood crossed the septum, mixed with air, and became vital spirit. Ibn al-Nafis’ correction implied that the pneuma-production mechanism needed revision, but the revision received little subsequent attention in the Islamic world.

Later Reception and Displacement

The pneuma tradition entered the Renaissance in two forms: as the established Galenic three-spirit physiology still taught in the universities, and as a broader philosophical concept of spiritus — a semi-material substance mediating between body and soul. Wolfe notes that spiritus was “perhaps the core notion” of Renaissance vital-matter theory, “omnipresent in authors from Ficino through Glisson and Cavendish,” deriving in part from Stoic pneuma: “spirits in this context are material but very fine, and increasingly in authors like Telesio and Glisson, they become loci of agency.”(Wolfe, Charles T., 2010-2015)

The anti-Galenic natural philosophers of the sixteenth century attacked the spirit doctrine from one direction. Temkin notes that Telesius and Campanella denied the tripartite soul and Galenic faculties in favour of a unitary heat-carrying spirit: “Voluntary movements and the actions attributed to the natural faculties by Galen were all caused by the spirit” — a single spirit, not three.(Temkin, 1973)

Harvey’s demonstration of the circulation of the blood in 1628 struck at the physiological heart of the pneuma system. His proof that blood circulated continuously through a closed vascular loop meant that the old model — in which venous blood was continuously produced in the liver, consumed by the tissues, and separately transported as pneuma through the arteries — was untenable. As Temkin puts it, Harvey’s work “prov[ed] Galen’s medical science untenable by overturning his foundational theory of how blood and pneuma moved through the body.”(Temkin, 1973) The liver was no longer the origin of the veins; the arteries were no longer pneuma-channels; the septum did not conduct blood; and the rete mirabile did not exist in humans. Every physical structure underpinning pneuma-production collapsed.

Yet the concept lingered. Galenism as clinical practice survived the destruction of Galenism as science by perhaps a century. The language of “spirits” persisted in medical discourse well into the eighteenth century, and the doctrine of the six non-naturals — which had been partly organized around pneuma as “surrounding air” — continued to be taught as hygiene into the early nineteenth century.(Temkin, 1973) The eighteenth-century Montpellier vitalists gradually dispensed with the specific language of spirits in what Wolfe describes as “a process one might see as a kind of secularization or naturalization,” though the underlying concern with what makes living systems different from inert matter remained.(Wolfe, Charles T., 2010-2015) In the East, the pneumatic framework persisted even longer: Unani medicine — Greek medicine in its Arabic modification — continued to teach the three-spirit doctrine, and Temkin notes that it “is still taught and practiced in Islamic countries.”(Temkin, 1973)

Wind, Breath, and Comparative Perspective

The history of pneuma cannot be fully understood without recognizing that wind and breath operated as fundamental medical categories across multiple ancient civilizations, not in Greece alone. Kuriyama observes that wind was once a central medical category in both Greek and Chinese traditions, blamed for a vast range of afflictions, yet the historiography of medicine has almost entirely ignored its significance.(Kuriyama, Shigehisa, 1999) The disproportion between the concept’s historical importance and its scholarly neglect is itself revealing.

In Chinese medicine, wind (feng) was declared “the chief of the hundred diseases” and suspected as a cause in nearly all afflictions, a scope that substantially exceeded wind’s role in Hippocratic medicine, where it served as one important cause among several.(Kuriyama, Shigehisa, 1999) Despite this difference in emphasis, both traditions shared a deep structural assumption: winds blowing around bodies were presumed to be intimately related to breaths sustaining life within, such that pneuma could denote both external wind and internal vital breath, and the Chinese terms feng and qi were frequently interchangeable in analogous ways.(Kuriyama, Shigehisa, 1999) Wind’s medical relevance in both cultures derived from its association with change itself: wind presaged, exemplified, and caused altered states, and medicine as the study of sickness naturally converged with wind’s dominion over transformation.(Kuriyama, Shigehisa, 1999)

To understand the specific texture of Chinese wind pathology, it is necessary to go back further than the medical texts. Shang-dynasty inscriptions (thirteenth century BCE) reveal that winds were not yet mere atmospheric phenomena: they were divine presences to which sacrifices were offered and whose retreat was sought through ritual. The direction from which they blew was crucial: the cardinal directions staked out distinct spiritual abodes imbued with distinct powers, and the winds ruling from them governed the metamorphoses of the world, determining the fate of royal hunts, battles, and harvests.(Kuriyama, Shigehisa, 1999) Medicine inherited this cosmological weight when it later classified winds as agents of disease; the pathological evil wind (xiefeng) was continuous with the theologically charged winds of Shang divination.

The two traditions nonetheless developed wind theories that were fundamentally different in structure. Greek medicine analyzed wind through qualities (dry/moist, hot/cold) that affected humoral balance, while Chinese medicine understood evil winds as independent invaders defined not by intrinsic qualities but by directional origin and seasonal identity.(Kuriyama, Shigehisa, 1999) The crux of the matter in Chinese wind etiology lay in timing: proper winds (zhengfeng or shifeng) were those that blew from the right direction in the right season (easterly in spring, southerly in summer, westerly in autumn, northerly in winter). Evil winds (xiefeng or xufeng) were those that contravened this seasonal order, blowing from the wrong direction for their time. They were evil because they violated the cosmic regularity that defined health; their intrusion was the intrusion of chaos into an otherwise predictable order.(Kuriyama, Shigehisa, 1999)

The spatial imagination of wind’s relationship to the body was expressed most concisely in the terminology of acupuncture. The sites needled in acupuncture practice are called xue in Chinese, a word that means holes, caverns, or hollows. The same term appears in the practice of fengshui (wind-and-water geomancy), where specialists diagnosing the flow of breaths across a landscape sought out xue: the best sites for the living to dwell and the dead to rest, identified as points where winds entered or exited the earth’s hollows. The naming was not accidental: the body in Chinese medicine was a landscape through which winds streamed in and out of strategic orifices, just as winds blew in and out of the caverns of the earth.(Kuriyama, Shigehisa, 1999)

The skin and pores formed the critical boundary in this landscape. Separating and protecting the body’s interior from the wind’s volatile intrusions were the skin and its pores, both the site of wind’s first attack and the marker of inner strength. The Lingshu observes that when the body’s protective breaths (weiqi) are harmonized, the sinews are flexible, the skin is pliant, and the pores closely knit (zouli zhimi). Those with thin skin and flabby flesh succumb to untimely winds; those with thick skin and firm flesh do not. The skin and pores simultaneously manifested the strength within a person and gave protection from the dangers without.(Kuriyama, Shigehisa, 1999) Health was a matter of being well-sealed against chaotic environmental incursion while maintaining an inner fullness that left empty winds no room to enter.

This divergence reflects a broader contrast in how each tradition conceptualized the relationship between body and environment. Over the course of Greek antiquity, pneuma underwent a trajectory of internalization, shifting from external wind shaping human life from outside (the Hippocratic period) to internal breath animating the body from within (Aristotle through Galen); this trajectory progressively placed the body beyond the direct influence of the environment.(Kuriyama, Shigehisa, 1999) Galen’s anatomical concept of organs as instruments of the soul (organa as tools for purposeful action) redefined the body as an autonomous entity organized for volitional activity, a conception that Kuriyama contrasts with the Chinese understanding of zang and fu as repositories rather than instruments.(Kuriyama, Shigehisa, 1999)

Chinese medicine held these pressures in productive tension rather than resolving them toward autonomy. It sustained two opposed ideals simultaneously: the resonance of microcosm and macrocosm (the body in harmonic relationship with cosmic winds and seasons) and the autonomy of the self from the world (inner fullness as protection against wind invasion), with health inhering in the balance between vulnerability and impermeability.(Kuriyama, Shigehisa, 1999) The Greek tradition, by contrast, moved decisively toward the internalized, instrument-organized body that Galen’s system exemplifies, a resolution that shaped Western physiology for fifteen centuries.

See Also

• humoral-theory
• galenic-medicine
• vis-medicatrix-naturae
• vitalism
• atomism
• six-non-naturals
• four-elements
• dissection-and-anatomy
• empiricism-in-medicine
• teleology-in-medicine

Sources

Evidence cards used in this entry:

Footnotes