The Energy of Life:

Empedocles (c. 490–c. 435 BC) was one of the greatest all-rounders of all time, exemplifying the enormous diversity and creativity of ancient Greek thinkers. Born to an aristocratic family in the city-state of Acragas, Sicily, he assisted in a coup against the oligarchy ruling the city and was offered the crown. He refused, establishing instead a democracy, and becoming himself a politician. But, in his spare time, he also managed to be one of the greatest poets, scientists, philosophers, and doctors of his age. As if this were not enough, after banishment and exile from his home state, he became a prophet and god. Legend has it that he could work miracles, control the winds, restore the dead to life, and killed himself by jumping into the volcanic crater of Etna to prove his divinity. Whether this leap did in fact prove this or not, history does not say, though apparently all that remained of Empedocles physically were his sandals. However, his thoughts remained to haunt the intellectual landscape for over two thousand years.

Empedocles devised the theory of the four elements, described as the most successful scientific theory ever, in terms of popularity and longevity, although it was not, of course, correct. It held that everything in the world consisted of a combination of only four elements. This theory appears to be a diplomatic compromise between earlier contradictory ideas that the world consisted solely of water (Thales), an unknown and unknowable substance (Anaximander), air (Anaximenes), or fire (Heraclitus). Empedocles suggested that there was not a single fundamental substance at all, but rather four elements (or ‘roots’ as he called them): earth, fire, air and water. The advantage of having four elements rather than one, was that it was obvious to anyone that the world consisted of an incredible diversity of things, and it was hard to explain this diversity if everything consisted of the same single substance. It was also difficult to explain how anything could change, if everything was, in essence, the same. Empedocles suggested that each different type of thing in the world consisted of different proportions of the four elements, and further that change was due to exchange of some of its constituent elements. For example, he said that bone was composed of fire, water and earth in the proportions 2:1:1 and flesh was composed of all the elements in equal proportions.

However, change could not just be left to the elements. After all, why should objects alter if there was only inert substance in the world? Why should rocks fall? Why should volcanoes explode? Why should thunder and lightning wrench the skies? Change was a big problem for the Greeks. It is also intimately related to energy, as energy can be thought of as the hidden source and cause of change. How were the Greeks to explain it without invoking gods or souls or minds? How could matter alone cause change? How could something new appear from nothing? Empedocles proposed that, in addition to the four elements, there were also two forces, which he called ‘love’ and ‘hate’. Hate (or ‘strife’) pushed things apart, while love pulled them together again; and when the two forces were balanced there was no change, a standoff. This sounds like a plot for a romantic novel, but Empedocles partly conceived of love and hate similarly to the modern conception of a force, as an inanimate pushing or pulling between matter. Thus, Empedocles’ overall conception of the world as consisting of different immutable elements, pushed and pulled by forces, so that change is due to chance and necessity rather than purpose, is strikingly similar to that of nineteenth-century physics. This similarity is no accident, of course, since the modern concept is partly derived from Empedocles.

Empedocles’ view of the world does, however, diverge radically from the modern in many ways: he also saw the two forces, love and hate, in a religious sense, as a struggle between good and evil (with the four elements each identified with a different god). His scheme of things also differs from ours in that his elements correspond more to the modern phases of matter (solid, liquid, gas, and plasma) rather than to modern elements (such as hydrogen, oxygen, nitrogen, and carbon). This difference partly arises from the fact that Empedocles appears to have rejected the idea of empty space – the void or vacuum – a space where there was nothing, no elements or anything else. Since he had shown that air was a substance, he saw no reason to believe in empty space between the elements. Thus he conceived of the elements as homogenous substances, which blended together when mixed, like different-coloured paints.

Earlier thinkers (such as Anaximenes) and later thinkers (such as Democritus) took the more modern view that a substance consists of a vast number of small particles separated by empty space, and conversion from liquid to gas is not due to a change of elements, but rather to the elements moving much further apart. Thus, ice consists of water molecules held rigidly together, while liquid water consists of the same water molecules flowing over each other, and steam, or completely evaporated water, consists of the same water molecules very far apart. The Atomists – Leucippus and Democritus (c. 460–370 BC) – pushed this view of the world to its most materialistic extreme, by taking Empedocles’ world, ridding it of its religious components, but adding the void. Thus, their view was that there was nothing in the world except a vast number of tiny particles (atoms) moving through empty space. Each of the four elements had a different shaped particle, and this shape determined the properties of the element. This explanation of the world had great advantages over the no-void view, because it could explain easily how the elements could mix and then separate: particles simply passed between each other; whereas this was hard to explain if there was no empty space between elements. Similarly, Empedocles had considerable difficulty explaining why the millions of things in the world had such startlingly different properties, if only differing in the proportions of the four elements. Why should a difference in proportions cause new properties? Democritus (and modern science) could explain this by the arrangement of the atoms within the object. New properties arose from new spatial arrangements or configurations of the atoms. There were an infinite number of ways of arranging atoms of four elements, and consequently an infinite number of possible things or materials. This is the essential secret of the success of modern chemistry and biology: explaining the properties of things in terms of the microstructure of the elements of which they consist. Unfortunately for the Atomists, the technological means did not exist in Greece to probe the microstructure of things, and thus test their theories.

We have been pursuing these ideas about matter, because they lie at the root of modern notions of energy. But Empedocles was far more than a creative physicist (physis was Greek for nature), he was also an inventive biologist (bios, Greek for life). According to Empedocles, the body’s flesh and blood consisted of equal proportions of all four elements, and these attracted similar elements from the environment. Thus, the same four elements constituted non-living and living matter, mind and the immortal gods. The blood circulated from the heart to the surface of the body, where air was taken in through the pores, and back again, alternately expelling and drawing in air. The motion of blood in and around the heart created thought, and so the heart was seen as the organ of consciousness. But Empedocles had a very concrete view of consciousness, seeing for example, thought as simply blood in motion. Perception occurred by elements in the blood meeting and mingling with the same elements in the environment. An external object was perceived by some elements from it entering the body and meeting the corresponding elements in the body, and their meeting or mingling was perception. Nutrition occurred through direct assimilation, that is, the elements of the body attracted similar elements in the environment to them, and these new elements fitted in place to form the growing body.

The theory of the four elements was astonishingly popular and long-lived, lasting from the fifth century BC until the chemical revolution of the seventeenth century. Yet it is hard to see quite why thinkers stopped at only four elements. Aristotle suggested a fifth – the ether – to compose all extraterrestrial things. The Chinese used five elements also (or phases): water, earth, fire, metal and wood. In modern science we have about 100 different chemical ‘elements’, which can combine to give an infinite number of possible molecules. But at the beginning of the twentieth century the Cambridge physicists J. J. Thomson, Ernest Rutherford, and James Chadwick discovered that these chemical elements were not in fact elements in the classical sense (fundamental and indestructible particles of matter), because they were destructible and composed of three simpler, indestructible particles – the proton, electron, and neutron. And these three particles were later found to interact via a fourth (short-lived) particle – the photon. Therefore, Empedocles’ four elements and two forces theory is, in outline, not that dissimilar to much more modern theories of the Universe.

Hippocrates (c. 460–377 BC) is called the founding father of medicine, and his theories of disease, cure and physiology influenced medicine and biology up until the eighteenth century. However, his own life is so mythologized that it is impossible to distinguish the basic events of his life, or even whether he really ever existed. According to legend, Hippocrates was a physician from Cos, and he practised medicine in Thrace, Thessaly and Macedonia, before returning to Cos to found a school of medicine. This school flourished from the late fifth century to the early fourth century BC, producing a vast number of highly original medical texts. Copies of around seventy of these books survive. These were conventionally attributed to Hippocrates, although he probably wrote none of them himself. The defining characteristic of Hippocratic medicine was its rejection of religious and philosophical explanations of disease, and its search for an empirical and rational basis for treatment.

Since prehistoric times, disease had been thought caused largely by gods, evil spirits, or black magic. A cure could thus be effected by ejecting the sin, spirit, or magic from the sufferer via various processes of purification. In Greece, traditional medicine was practised by priest-physicians in temples dedicated to the god Asclepius. In these temples of health, disease was apparently diagnosed partly on the basis of dreams and divination, and partly on the symptoms. Cures were half rituals and spells, and half based on fasting, food, drugs and exercise. According to later legend, Hippocrates was descended from the god Asclepius and brought up on Cos as son of a renowned priest-physician. The relationship between secular medicine (represented by Hippocrates) and religious medicine (based on faith healing or magic) in ancient Greece is difficult to discern, although apparently not as antagonistic as today.

Hippocrates and his followers accepted the doctrine of the four elements as an explanation for the natural world, but their concern as doctors was with disease’s causes and treatment. The four elements – earth, fire, air, and water – cannot be seen in anything approaching a pure form in or on the body. Also they knew relatively little about the inside of the body, because dissection was prohibited on both religious and ethical grounds. So the Hippocratics concerned themselves with what they could see and use in the diagnosis of disease, particularly the bodily fluids: blood, saliva, phlegm, sweat, pus, vomit, sperm, faeces and urine. Gradually the doctrine evolved that there were only four basic fluids (humours): blood, phlegm, yellow bile, and black bile. Blood can appear in cuts, menstrual flow, vomit, urine or stools. Phlegm is the viscous fluid in the mouth (saliva) and respiratory passages and comes out through the mouth and nose in coughs and colds. Yellow bile is the ordinary bile secreted by the liver into the gut to aid digestion; it is a yellow-brown fluid that colours faeces. The identity of black bile is not entirely clear, perhaps originally referring to dark blood clots, resulting from internal bleeding, which may appear in vomit, urine or faeces. However, the four humours did not only refer to these particular fluids, but were thought to be the body’s basic constituents. Health was thought to be due to the balance of these humours, and ill health an imbalance of the humours. Epilepsy was, for example, thought to be caused by an excess of phlegm in the brain blocking the flow of pneuma (vital spirits) to the brain. Thus treatment sought to restore the balance between the humours by removing the humour that was present in excess, for example by bloodletting, purging, laxatives, sweating, vomiting, diet or exercise.

The four humours (blood, phlegm, yellow bile, and black bile) were associated with the four elements (air, water, fire and earth), the four primary qualities (hot, cold, dry and wet), the four winds, and the four seasons. A predominance of one humour or the other gave rise to four psychological types. Thus, the ‘sanguine’ type, resulting from a dominance of blood, was cheerful and confident. ‘Phlegmatic’ types (with too much phlegm) were calm and unemotional. ‘Choleric’ or ‘bilious’ people (with too much yellow bile) were excitable and easily angered. ‘Melancholic’ types (too much black bile) were, obviously, melancholy, that is sad or depressed, with low levels of energy. This was the earliest psychological classification of character or temperament, and was used to categorize different people right up until modern times. No obviously superior way of classifying temperament has, in fact, yet been devised. The theory of the four humours dominated medical thinking until about three hundred years ago. Many patients were still being bled even in the nineteenth century.

The Hippocratics and Greeks generally believed in positive health – health could be improved much further than the absence of illness towards well-being. Modern medicine is mainly concerned with negative health (i.e. illness), and how to restore us to health, rather than with helping us feel ‘on top of the world’. The Hippocratics were much concerned with regimen or lifestyle, both in health and disease, mainly involving the correct balance of food and exercise. The importance of exercise to both physical and mental health was recognized, and was institutionalized in gymnasia where exercise was practised on a social basis. If you had gone to Hippocrates in 400 BC (assuming you could find him) complaining of lack of energy he might have given you a detailed regimen involving an exercise programme, with a warning about too much or the wrong type of exercise; a diet, particularly including strained broths; a lot of hot and/or cold baths, and massages; some sex (if lucky); and some obscure advice about the relations between your energy and the wind direction, season of the year, etc. This would have been, in general, a reasonably effective regimen, and you would be lucky to get better advice today from your doctor.

Aristotle (384–322 BC) was a colossus of thought, straddling the end of classical Greece and Renaissance Europe. He dominated the world of the intellect, sometimes as a benign sage and other times as malevolent dictator. His thoughts were worshipped to such an extent that they circumscribed any attempts at original thought, until their eventual rejection by Renaissance Europe, when he was blamed for stifling two thousand years of thought. Much of Aristotle’s influence derives from his having been a pupil of Plato (possibly the greatest thinker ever), and then tutor to Alexander the Great (possibly the most successful conqueror of all time).

Aristotle’s views of the physiology and energies of life were derived mostly from Empedocles, Hippocrates and Plato. Nutrition, vital heat and pneuma (vital spirit) were pivotal to this view. The heart was central to the body, the origin of consciousness and the instrument of the soul, and the source of heat, pneuma, blood, and movement for the rest of the body. Pneuma was an air-like substance or spirit, containing vital heat, which was always in rapid motion, and as such was a source of both heat and motion inside the body. Pneuma was derived from air, and brought through the mouth, nose and skin to the heart, where it supplied the vital heat. A steady flow of nutrient fluid from the gut supplied the heart, and the heating of the fluid within the heart produced blood. The blood and pneuma were then distributed through vessels to the rest of the body, where the blood coagulated to form the tissues of the body under the influence of the ‘nutritive soul’. There was no circulation of blood, rather the blood was produced in the heart (and liver and spleen) and then distributed to the tissues, with no return flow. Many vessels (the arteries) were thought to be hollow (as indeed many are if the blood escapes from them after death), and were, thus, thought to carry air or pneuma through the body. The brain cooled the blood, and functioned to prevent the blood from overheating. The muscles were simply a protective layer, keeping the rest of the body warm, and had no function in movement. Nerves, as such, were unknown, as most are difficult to see; but large nerves and tendons were collectively called neura and were thought to function in movement of the limbs, by acting as cords pulling the bones. The pneuma supplied the ‘go’, energy or movement throughout the body.

Aristotle’s pneuma was also the motivating force outside the body – in the physical world. According to his mechanics, the natural state of things was rest rather than movement; so that the continuous movement of an object such as an arrow in flight required pneuma to be continuously pushing the arrow from behind. Thus we can see that pneuma was energy for Aristotle, although of course it had a rather different role in classical thinking. Aristotle was also partly responsible for the theory of the four qualities: hot, cold, wet, and dry, which were components of the four elements. Thus earth was cold and dry, water cold and wet, air hot and wet, and fire hot and dry. This became a very important doctrine in later medicine and alchemy, because it gave a key as to how to alter the ratio of the elements; thus, for example, water could be converted to air by heating, or air could be converted to fire by drying.

Aristotle was the first authority to use the term energeia, from which we derive the word ‘energy’. But he used it to mean the ‘actual’, as opposed to the ‘potential’, as he had an obscure theory that ‘change’ involved turning from a potential thing into an actual thing. So when something happens, a potential happening changes into an actual happening. Thus for Aristotle energeia was tied up with change and activity, but in what seems now a rather obscure and abstract way.

Although Aristotle’s view of physiology and energetics was most influential, it was far less original and interesting than that of Plato. Plato was not really interested in physiology, as he had his mind set on higher things, but he wanted to find a physical location for the various parts of the soul that he had identified. For, according to Plato, the body is peopled by a bickering community of souls, ruled over by a somewhat prissy head. The immortal soul is in the head, and the mortal soul located from the neck down. The courageous part of the mortal soul is found above the diaphragm, where it can both listen to reason (from the head) and subdue the lower regions. This soul’s main home is the heart; when the head thinks that the passions are out of control it informs the other organs, and the heart starts leaping with excitement and overheating. The lungs can then save the day by cooling and providing a cushion for the overtaxed heart. Below the diaphragm dwells the ‘appetitive’ soul, which while necessary for life needs to be kept chained, far from the seat of reason. This part of the soul is controlled by the liver, capable of listening to reason. The liver regulates the nether regions either by contracting to block passages causing pain and nausea, or by spreading cheerfulness and serenity to the surrounding parts of the soul. The length of the gut is intended to prevent food passing through too quickly, which would cause an insatiable appetite, and make mankind impervious to culture and philosophy. The spinal marrow is called the universal ‘seed-stuff’ (also the source of semen) fastening the soul to the body. The different kinds of soul are found in various parts of the marrow, while reason and intellect occupy the brain. This community-of-souls theory of the body shows how appealing, but empty, intentional explanations of physiology can be. In order to progress, the supernatural had to be replaced by mechanical causes and energy as the source of change.

The deaths of Aristotle and Alexander in 322 and 323 BC respectively marked the end of classical Greece. But Alexander had spread Greek culture across the known world, ushering in the age of Hellenism, which was a fusion of Greek and Persian culture. Hellenism’s most successful centre was in Alexandria, briefly flourishing under Ptolemy I. A former pupil of Aristotle, Ptolemy attracted some of the greatest Greek scientists and thinkers to Alexandria’s Museum and Library. Two brilliant physicians, Herophilus and Erasistratus, were able for the first time to practise dissection of the human body there and used this to great effect. This had been impossible previously due to the commonly held assumption that the body retained some sensitivity or residual life after death. Changing beliefs about the soul’s relation to the body enabled Herophilus and Erasistratus to dissect dead humans, and even, it has been claimed, live criminals. The result caused a revolution in anatomy: the exploration of a whole new realm below the human skin. The nerves, and their relation to the brain and muscles, were discovered. The brain was explored and the fluid-filled cavities within (ventricles) were thought to be filled with a new form of pneuma: psychical pneuma (animal spirits). This psychical or mind pneuma radiated out from the brain, through the nerves, to energize the muscles. However, Alexandrian scientific creativity gradually declined and the influence of eastern mysticism increased.

In the second and first centuries BC, Rome swept the political stage while largely adopting Greek culture and thinking. Into this new world was born Galen (AD c. 129–216), antiquity’s last great physician and biologist. An architect’s son from Pergamon, he studied philosophy then went to Alexandria to learn dissection. Returning to Pergamon, he became surgeon to a school of gladiators, where he gained invaluable experience in treating wounds. In AD 169 Galen was summoned to Rome to become personal physician to Marcus Aurelius, the Philosopher Emperor. These duties do not seem to have been too onerous as Galen continued his writing and scientific work, in the end producing over 130 books. Many are commentaries on and syntheses of previous medical knowledge, including textbooks and treatises on almost all diseases, treatments and methods of diagnosis. These books became the central texts of medicine for fifteen hundred years. Galen was seen as a kind of medical theologian, for whom anatomy was both praise and veneration of the one true God. And this, twinned with his interpretation of the body in Aristotelian terms, guaranteed the acceptance of his writings by later Christian and Islamic authorities.

Galen’s doctrine of pneuma synthesizes earlier ideas of the Hippocratics, Aristotle, the Alexandrians and Stoicism (a philosophy founded by Zeno). Pneuma can be translated as ‘airs’, and was thought to be an invisible force within the air. Pneuma was translated into Latin as spiritus, but is most naturally translated today as ‘energy’. To the Stoics, pneuma was a non-material quality or form imposed on matter. Pneuma pervaded the universe and was the vehicle of cosmic ‘sympatheia’, by which each part of the universe was sensitive to events in all others. Pneuma acted as a force field in the air, immediately propagating movement to the edge of the universe and then back again. This is reminiscent of modern concepts of sound waves or of electromagnetic waves moving through the air. Inside the body, pneuma pervaded the blood vessels and nerves and enabled the transmission of sensitivity, movement and energy.