What is Life? It is Erwin Schrodinger's question. His answer was that life is a system that feeds on negative entropy. Herbert Spencer defined life as ‘the definite combination of heterogeneous changes. both simultaneous and successive’. Jacques Loch thought that living things were chemical machines ‘consisting essentially of colloidal material. which possess the peculiarities of automatically developing. preserving. and reproducing themselves’. Hermann Muller though: that any entity that had the properties of multiplication, variation and heredity was alive. For the authors of any biology textbook that you care to pick up it is a rather arbitrary list of properties: metabolism, nutrition, reproduction and so on; for most biologists it is a question best ignored. Aristotle asked Schrodinger’s question, and answered it. At first he gives the conventional list of properties: ‘By life we mean the capacity for self-nourishment, growth and decay.’ But that doesn’t really capture the terms in which he analyses the problem. He’s after a much more abstract description of what it is that separates the living from the dead His deeper answer is that living things, uniquely, have a soul.
LIV
THE TRADITIONAL GREEK conception of soul was Homer’s. Patroclus falls at Troy and his disembodied soul takes wing for the House of Hades. Perhaps this explains why the Greek name for a butterfly is the same as that for ‘soul' -psyche -for, as the soul flees a corpse at death. so a butterfly clambers from its Chrysalis.
In The Phaedo Plato elaborates the traditional theory. The soul is no longer merely something lost when we die; it reasons and regulates the body‘s desires while we are alive. Now it is Socrates who is dying. His soul too will leave the body in which it is trapped and travel to Hades. but where Patroclus' soul will live, at best, a kind of feeble afterlife, Socrates' soul can look forward to the prospect of perpetual reincarnation or so he optimistically argues. In The Republic the soul gains further complexities. It becomes the seat of moral virtue. Plato describes the human soul as being mutilated by evil rather as the sea monster Glaucus evidently modelled on a species of spider crab is weighed down by the shells and seaweed encrusting it.
Fragments of Aristotle's youthful works tell of similar beliefs. A dear friend. Eudemus. had died on a Sicilian battlefield. In a monograph devoted to his memory, Aristotle has Eudemus' soul returning to its home. Another early work, the Protrepicus compares the relationship between body and soul to the unpleasant Etruscan habit of binding their captives face to face with a corpse -the soul being the living partner in this macabre pas de deux.
Of this passage one scholar said, ‘Surely we are here in the presence of a sick. if strong and beautiful, mind.’
Later in life, Aristotle wrote a whole book about the soul, de Anima, or The Soul. Devoid of Platonic moralizing, it is resolutely scientific in tone:
Some types of knowledge may be especially fine and worthwhile for their precision or because their objects have greater value and elicit greater wonder. It is for both these reasons that we should treat the study of the soul as one of extreme importance. However its investigation seems to be of special importance for truth as a whole and the study of nature in particular. For souls are the principle of animal life.
This. to us. is a very strange, even suspect, claim. ‘Soul’ is a word burdened with many meanings but none in modern science. Perhaps we would do better to abandon translation, but mere transliteration hardly helps matters at all For us, ‘psyche’ refers to mental states -in particular, consciousness. To be sure, Aristotle does treat mental states in his book but he treats them as physiology: the Cartesian problem of consciousness hardly arises.
Indeed. The Soul is not a psychological treatise at all. but his most general statement about the systems of command and control that enable living things to do what they do.
Aristotle asserts, with fairly little argument. two propositions: that all living things ... plants, animals and humans .. have souls: and that. when a living thing dies, its soul ceases to exist. These were probably commonplace among fourth-century Greek intellectuals. Plato clearly believes the first and has to argue against the second. But what, exactly is the soul? Aristotle begins by surveying his predecessors views.
Everyone, he says, agrees that souls are associated with movement: the ability of living things to breathe, grow, wriggle, swim, walk and fly. A good account of the soul should be able to explain how. He considers the popular idea that souls are made of some physical matter. The usual candidates for soul-stuff are the elements: air, water or fire -only earth seems to be missing as a candidate soul'stuff. He rejects them all. Quite reasonably, he cannot see how any element is capable of making an animal move. He considers Democritus' argument that movement is due to the restless motion of the spherical atoms that comprise creature’s souls_ That. says Aristotle. is about as sensible as Daedalus’ scheme for animating a wooden statue of Aphrodite by pouring molten silver into it‘ Elements are the stuff that souls operate on; they are the substrate of life ~not life itself.
He also considers some less mundane ideas. One, proposed by a renegade Pythagorean, is that the soul is a harmony Aristotle interprets this to mean that it is a particular ratio of elements. This idea also strikes him as simplistic. Yet he sees some merit in it. It has something in common with his own theory insofar as it depends not on the properties of matter per se, but rather on the way in which matter is arranged. For Aristotle, when he comes to give his own theory, argues that the soul of a living thing is its form its eidos in its body.
I have argued that, when Aristotle speaks of the ‘form’ or ‘formal nature’ of a creature, he often means the information required to order matter into a creature of a given kind. This interpretation is based not only on the various analogies he gives (imprints in wax; letters and syllables), but also on the fact that forms are present even when they are invisible. They are somehow present in an animal’s seed and are responsible for the development of the embryo and the appearance and functions of the adult. So an animal’s soul is its form, albeit under particular circumstances:
"If we must say something general about all types of soul, it would be the first actuality of a natural body with organs."
The key word here is ‘actuality’ entelekheia. It is this word, a bit of Aristotelian jargon, that is most distinctive about his theory of the soul. He often uses it in opposition to ‘potentiality’ dynamis opposition runs deep into his physical theory. Any change, in Aristotle’s view, is the actualization of a potential. Thus when he says that the soul is an actuality, he's stressing the fan that it's something that previously existed only potentially; that it‘s something that comes into being From something else. When combined with the claim that the soul of a living thing is ‘its form in its body'. it becomes clear that he means that the forms of unfertilized seed are mere potentials; and that those forms when realized in growing embryos and functioning adults are souls.
This is still irritatingly abstract. But Aristotle tells us much about the properties of souls and they. in turn. tell us what he's getting at. Some properties are quite general and apply to all that souls do in all creatures; others are more specific and apply just to humans. Four of them are particularly revealing.
First, an Aristotelian soul is not made of matter. That’s clear from his objection to Democritus’ crude materialism, but it also follows from his definition of the soul as the form in a body’. Second, the soul is associated with the presence of organs, which means that it is a functional property of living things. Third, the soul is responsible for change in living things. By this he means that it regulates the body’s processes: growth, maintenance, ageing, locomotion, sensation, emotion and thought itself. Finally, the soul is responsible for a creature’s goals, ultimately its survival and reproduction.
Aristotle’s use of entelekheia to describe the soul tells us how important he thought this was, for the word is partly derived from telos, an end or goal. This conception, too, runs deep into his metaphysics. The soul, he says. is ‘an entity [ousia] in the sense of a definition [logos]’. By this he means that a living thing’s soul is the sum of its functional features. If an eye were a living creature, he says, then its soul would be vision. He is so committed to the idea that functional features define a creature (or an organ), rather than the stuff it’s made of, that he even says that if an eye can’t see (because it’s damaged) then it really isn’t an eye at all. It’s an eye ‘in name only’, like the ‘eyes’ that Greek sailors paint on the prows of their ships.‘ He insists that a corpse isn’t a man at all since it does not have a soul. From this point of view, a male cuttlefish who copulates with a dead female is not only wasting his time but making a serious philosophical mistake.
and
Aristotle is trying to root out the ‘homunculus’. He is attacking the notion that there is within us all a small, disembodied person -an I- who is thinking our thoughts, hating our hates, loving our loves and controlling, in some mysterious fashion, our bodily machines. He does not have Descartes’ problem of explaining how an immaterial soul moves the body.
In the biological version of the ‘spiritual soul', Aristotle is a vitalist. To be a vitalist is to suppose that living things have some property that cannot be found in, or derived from, inanimate matter; to deny that living things are really just very complicated machines; to believe in the autonomy of life. In the eighteenth and nineteenth centuries a battle raged particularly in Germany between biologists and philosophers who thought that living things are just machines and those who did not. The latter were invariably impressed by the very thing that so impressed Aristotle: the goal’directness of living things. Teleology was an invitation to fill the explanatory vacuum with resounding, if empty, phrases: vis vitalitis, vis essentialis and the like. The last scientist of any repute to wear the vitalist badge proudly was Hans Driesch (1867-1941). A brilliant experimentalist in his youth, one of the founders of experimental embryology- in middle age he abandoned mechanistic theory and became a committed vitalist, arguing that no machine could even in principle construct a living thing. ‘But this may mean no more than that the living machine is more complex than any that Driesch has in mind,’ was Edward Conklin’s sardonic quip in 1914, and now Driesch is known, if at all, only as an object lesson on the perils of abandoning the lab bench for the airy realms of philosophy. In an unfortunate homage to Aristotle, Driesch called his vital force entelechy.
Mind-body dualists may still lurk in the darker recesses of philosophy departments, but in biology vitalists are extinct. The goal-directness of living things has been explained by natural selection, which tells us why living things have goals and what those goals are, by physiology and biochemistry which tells us how they achieve those goals and by genetics which tells us where those goals are stored and how they are transmitted from parent to child. Aristotle’s final, moving and formal causes all the work that he attributed to the soul ~ have been absorbed by, and divided among, the branches of biology. The question, then, is this: did Aristotle, ignorant of this seamless hierarchy of explanation, succumb to Kantian despair and press a traditional word, ‘soul’, into service as a placeholder for the gap between inanimate material and all the things that living things do? If so, then he is a vitalist. Or did he use ‘soul’ as a term to embrace the processes by which living things develop and function; processes that he thought rightly or wrongly were perfectly explicable in terms of the physical science of his day? lf so, then he is a materialist albeit of a very sophisticated kind.
It is sometimes said that all modern biologists are ‘materialists’ insofar as all our explanations take account of the brute properties of matter ~ chemistry and physics. But no biologist is a naive, Democritean, materialist, for all agree that the distinctive properties of living things depend on the arrangement of matter. The elements, though necessary, are not sufficient for life. An ordering principle information is needed as well. We are, to coin a term, ‘informed materialists’.
That was Aristotle’s view as well. It is why he identifies psyche as the actualization of eidos. It is only a beginning. Soul appears in his book on developmental biology and heredity The Generation Jof Animals; in his book on animal locomotion The Movement of Animals; in his functional anatomy The Parts of Animals; and, most of all, in his physiology The Length and Shortness of Life and Youth andOld Age, Life and Death. Soul, in short, pervades Aristotle’s biology. When we survey all that he says about its workings it becomes apparent that he has given a detailed and coherent account, embracing many levels of biological organization, of how animals abstract matter from the environment, transform it, distribute the transformed matter throughout their bodies and use it to grow, maintain themselves. reproduce, perceive the world and respond to it and that the form, structure or organization of all this activity is the soul.
The result is a vision that is at once disturbingly alien and surprisingly familiar. It is alien when we consider that we have been talking about ‘soul’. a word that by religious and philosophical tradition is usually applied to entities only tangentially connected to the physical world, if at all; but it is very familiar when we ignore the word itself and attend to what Aristotle is trying to understand the moving principle of life.
and
It is sometimes said that Cuvier got his teleology from Kant, but for Kant teleology was just a ‘heuristic fiction’ and an invitation to despair. ‘There Would never be’, he said, ‘a Newton capable of explaining a blade of grass.’ Cuvier was more sanguine. ‘Why should not natural history also have its Newton one day?’ (‘And now it’s got one’ was his unspoken reply) One can feel a pang of sympathy for Cuvier. If natural history has a Newton, it’s Darwin who, in the Origin, is generous even as he puts his predecessor in his place:
The expression of conditions of existence, so often insisted on by the illustrious Cuvier, is fully embraced by the principle of natural selection. For natural selection acts by either now adapting the varying parts of each being to its organic and inorganic conditions of life; or by having adapted them during long~past periods of time: the adaptations being aided in some cases by use and disuse, being slightly affected by the direct action of the external conditions of life, and being in all cases subjected to the several laws of growth."
Notice how subtly Darwin changes Cuvier’s meaning. When Cuvier invokes the conditions of existence he is generally trying to explain the fit of an animal’s parts to each other; when Darwin does, it is to explain the lit of an animal’s parts to its environment. The difference is only one of emphasis. Anyone who seeks to understand the design of living things necessarily studies them as wholes in themselves and in their worlds; the three great students of animal design, Aristotle, Cuvier and Darwin, all kept at least an eye to both.
In the Origin Geoffroy’s Law of Compensation appears under the heading ‘correlation of growth’. ‘I mean by this expression’, says Darwin, ‘that the whole organisation is so tied together during its growth and development, that when slight variations in any one part occur, and are accumulated through natural selection, other parts become modified.’ Darwin’s idea is more general than Geoffroy’s, for he allows that the connections need not be economic. But he credits him (and Goethe) for the insight.
These concepts continue their scientific run. But they have transmuted again, for if Aristotle, Cuvier and Geoffroy all wrote on the far side of 1859, Darwin joins them in writing on the far side of 1900 or, if you prefer, 19533‘ Aristotle’s principle of conditional necessity is now just as often applied, if not by that name, to molecules or even genes.
and
AESCHYLUS WAS VlSITlNG Sicily when an eagle, mistaking his bald head for a rock, dropped a tortoise on it and killed him. The tortoise probably died too since the only part of the story that’s certainly true is that golden eagles do seize tortoises, carry them aloft and release them in order to crack them open like nuts. Neither the playwright nor the tortoise matters here; one is only an accidental anvil and the other is food; the interest of the story is how the eagle accomplished this feat.
A neurophysiologist, sketching the mechanisms involved, would describe a causal chain that begins with a goal (bodily maintenance), that requires an appetitive motivational drive’ (hunger), perception (of the tortoise and Aeschylus’ head), a variety of computations (how and when to seize, carry and drop the tortoise) and motor’responses to execute them by. He would say that the physiology underlying some of these processes is well understood, that some of them are obscure, and that how it all works together is quite unknown. He would point out that we struggle to give a computational model of a worm wriggling across a petri dish never mind an eagle on the hunt.
Aristotle also attempts a mechanistic explanation of animals in motion. He sketches how the senses work, how they transmit information to the sensorium, how this information is integrated with respect to the animal’s goals and how it is transformed into mechanical action in its limbs. This system has even been given (by two classical philosophers) a very scientific’sounding acronym, the CIOM model‘ which stands for Centralized Incoming Outgoing Motions. Aristotle simply calls it the sensitive soul. By any name its anatomy is hazy, its physiology wrong. but its structure percipient.
Perception obviously requires the transmission of information about the world from the world to within an animal. As Aristotle puts it, perception is the transmission of an object’s form without its matter. This process begins with the five senses: sight, smell, taste, hearing, touch and their respective organs. He assumes that perception involves a qualitative change in a sense organ. That implies that the perceived object must make contact with it.
It’s easy to see how contact-dependent change works in touch, taste, hearing and, perhaps, smell. Vision is trickier. Empedocles and Plato argued that the eyes contain a fire and that light rays from this fire travel to the object of sight. Aristotle trenchantly points out that if this torch-beam theory were true, we’d be able to see in the dark. We might reasonably assume that his own theory of light is merely the reverse: that light rays emanate from some source and enter our eyes where they effect some change. That, however, is Newton, not Aristotle.
Aristotle supposes that some media air and water have the property of being either opaque or transparent. When such a medium is exposed to the sun or a fire it becomes transparent. Light, then, is not a ray, a wave or a particle, but a quality, an actualization of a potential. When we look at an object through a transparent medium, its shape and colours initiate movements in the medium that travel to our eyeballs where they effect a change.
Each sense organ perceives certain kinds of changes in the world; this specificity depends on the elemental composition of their uniform parts. To perceive colour and shape, eyeballs must be transparent and so are made of water; to perceive touch, flesh must be made of something solid and so is made of earthy stuff. His account of what actually happens in the eyeball when we see some object is quite opaque. He probably believes that the eyeball undergoes a physical transformation of some sort. Certainly he supposes that contact with sense organs initiates a chain of physical consequences that reach into the body.
The target of this chain is the central sensorium. the locus of perception itself. By ancient anatomical tradition, Plato thought the central scnsorium was the brain and. For once, Plato was right. Aristotle, of course, supposes that it is the heart. His main argument for this is that there should be a single. central principle of all the soul’s Functions. To make his theory work, he obviously needs a physical connection between the heart and the peripheral sense organs. You might expect him to appeal to nerves, but he doesn’t know about them. (He uses the term neuron but applies them to sinew; Herophilus would identify nerves as a distinct tissue in the following century) Aristotle therefore supposes that sensory transmission operates via the network of blood vessels as well as various ‘channels’. Most of these ‘channels’ do not obviously correspond to anything in modern anatomy, but one of them is probably, to use its modern name, the optic nerve. His argument rests on the fact that if it is severed by a blow to the head, blindness follows as if a lantern had been snuffed out. It’s unclear whether he thinks that sensory information is transmitted by the vessels channels themselves, the blood or some’ thing else; in any event, physical continuity between the peripheral sense organ and the central sensorium is essential.
The core functions of the sensitive soul take place in the heart. It’s where raw perceptions are translated into mental representations which, When added to desires, become actions. Aristotle assumes that the sensitive soul’s function is to maintain the animal’s wellbeing by ensuring, inter alia, that it gets enough to eat and that it doesn’t get eaten itself. Animals therefore experience the world in terms of pleasure or pain, as defined by the goal of self-maintenance. The eagle perceives the tortoise with pleasure; the tortoise perceives the eagle with pain. However, a given perception may be either pleasant or painful depending on the animal’s internal state: an eagle sated on tortoises may disdain another one.
The term that Aristotle uses for the mental representation of some object is phantasia. To explain, he personifies: ‘ “I have to drink,” says desire. “Here’s drink,” says sense-perception or phantasia or thought.’ He does not, Of course, give a mechanistic account of phantasia or any other higher cognitive process, but he recognizes the difficulty. After explaining the physiology of smell, he says, ‘but smelling is more than such an affection by what is smelly- what more? Is not the answer that, while the air owing to the momentary duration of the action upon it of the smelly thing does itself become perceptible to the sense of smell, smelling is an observing of the result produced?’ Indeed.
Phantasia and desire may be black boxes, but when he explains how he effects action, he becomes very physiological again. Heating and cooling of the heart accompany both of these mental events. These thermal changes initiate motionthat is then transmitted to the limbs. To explain how
he invokes devices that he calls automatic puppets:
The movement ofanimals is like that ofautomatic puppets, which are set moving when a small motion occurs: the cables are released and the pegs strike against one another . . . For they [animals] have functioning parts that are of the same kind: the sinews and bones. The latter are like the pegs and the iron in our example. the sinews like the cables. When these are released and slackened the animal moves. Now in the puppets . . . no qualitative change takes place . . . But in animals the same part has the capacity to become both larger and smaller and to change its shape; the parts change qualitatively when they expand because of heat and contract again because of cold.
The important point about these puppets is that they are automatic (automata). They seem to have been mechanical dolls of some kind. He’s careful to note that their motions aren’t exactly like those of animals since animal motions also involve qualitative change such as expansion and contraction of the kind found in the heart. This gives him another anatomical problem. He has to translate qualitative changes in the heart into mechanical changes and then distribute those mechanical impulses to the limbs, and he has to do this not only without nerves but also without muscles.
It’s not that the Greeks were oblivious to muscles. Classical statues of athletes and heroes display them in enviable relief. Hippocratic texts refer to muscles as myes ‘mice’ but are vague about what they do. Aristotle avoids the term altogether and calls them sarx ‘flesh’ -which he supposes has mostly a sensory function. His effectors of local motion are, then, sinews and a substance called symphyton pneuma.
Variously rendered ‘connate pneuma’, ‘hot breath’, ‘spirit’ or simply EP, pneuma is one of the most mysterious, yet powerful, substances in Aristotle’s chemistry It is something like hot air, but its heat is of a special kind, not the heat of conventional fire. It is analogous to the divine ‘first element’
(aither) of which stars are made. More mundanely, it gives organic materials special properties: olive oil is shiny, floats on water and does not freeze thanks to its high pneuma content.
