Realism is essential to common sense. Common sense, or enlightened common sense, distinguishes between appearance and reality. (This may be illustrated by examples such as ‘Today the air is so clear that the mountains appear much nearer than they really are.’ Or perhaps, ‘He appears to do it without effort, but he has confessed to me that the tension is almost unbearable.’) But common sense also realizes that appearances (say, a reflection in a looking glass) have a sort of reality; in other words, that there can be a surface reality - that is, an appearance - and a depth reality. Moreover, there are many sorts of real things. The most obvious sort is that of foodstuffs (I conjecture that they produce the basis of the feeling of reality), or more resistant objects (objectum = what lies in the way of our action) like stones, and trees, and humans. But there are many sorts of reality which are quite different, such as our subjective decoding of our experiences of foodstuffs, stones, and trees, and human bodies. The taste and weight of foodstuffs and of stones involve another sort of reality, and so do the properties of trees and human bodies. Examples of other sorts of this many-sorted universe are: a toothache, a word, a language, a highway code, a novel, a governmental decision; a valid or invalid proof; perhaps forces, fields of forces, propensities, structures; and regularities. (My remarks here leave it entirely open whether, and how, these many sorts of objects can be related to each other.)
My thesis is that realism is neither demonstrable nor refutable. Realism like anything else outside logic and finite arithmetic is not demonstrable; but while empirical scientific theories are refutable [see selection 8 above], realism is not even refutable. (It shares this irrefutability with many philosophical or ‘metaphysical’ theories, in particular also with idealism [as pointed out in selection 16].)
But it is arguable, and the weight of the arguments is overwhelmingly in its favour.
Common sense is clearly on the side of realism; there are, of course, even before Descartes - in fact ever since Heraclitus - a few hints of doubt whether or not our ordinary world is perhaps just our dream. But even Descartes and Locke were realists. A philosophical theory competing with realism did not seriously start before Berkeley, Hume, and Kant.1 Kant, incidentally, even provided a proof for realism. But it was not a valid proof; and I think it important that we should be clear why no valid proof of realism can exist.
In its simplest form, idealism says: the world (which includes the present reader) is just my dream. Now it is clear that this theory (though you will know that it is false) is not refutable: whatever you, the reader, may do to convince me of your reality - talking to me, or writing a letter, or perhaps kicking me - it cannot possibly assume the force of a refutation; for I would continue to say that I am dreaming that you are talking to me, or that I received a letter, or felt a kick. (One might say that these answers are all, in various ways, immunizing stratagems [of the kind described on pp.l25f. above]. This is so, and it is a strong argument against idealism. But again, that it is a self-immunizing theory does not refute it.)
Thus idealism is irrefutable; and this means, of course, that realism is indemonstrable. But I am prepared to concede that realism is not only indemonstrable but, like idealism, irrefutable also; that no describable event, and no conceivable experience, can be taken as an effective refutation of realism.2 Thus there will be in this issue, as in so many, no conclusive argument. But there are arguments in favour of realism*, or, rather, against idealism.
(1) Perhaps the stongest argument consists of a combination of two: (a) that realism is part of common sense, and (b) that all the alleged arguments against it not only are philosophical in the most derogatory sense of this term, but are at the same time based upon an uncritically accepted part of common sense; that is to say, upon that mistaken part of the commonsense theory of knowledge which I have called the ‘bucket theory of the mind’ [see selection 7, section iv, above].
(2) Although science is a bit out of fashion today with some
people, for reasons which are, regrettably, far from negligible, we should not ignore its relevance to realism, despite the fact that there are scientists who are not realists, such as Ernst Mach or, in our own time, Eugene P. Wigner;3 their arguments fall very clearly in the class just characterized in (1 )(b). Let us here forget about Wigner’s argument from atomic physics. We can then assert that almost all, if not all, physical, chemical, or biological theories imply realism, in the sense that if they are true, realism must also be true. This is one of the reasons why some people speak of ‘scientific realism’. It is quite a good reason. Because of its (apparent) lack of testability, I myself happen to prefer to call realism ‘metaphysical’ rather than ‘scientific’.4
However one may look at this, there are excellent reasons for saying that what we attempt in science is to describe and {so far as possible) explain reality. We do so with the help of conjectural theories; that is, theories which we hope are true (or near the truth), but which we cannot establish as certain or even as probable (in the sense of the probability calculus), even though they are the best theories which we are able to produce, and may therefore be called ‘probable’ as long as this term is kept free from any association with the calculus of probability.
There is a closely related and excellent sense in which we can speak of ‘scientific realism’: the procedure we adopt may lead (as long as it does not break down, for example because of anti-rational attitudes) to success, in the sense that our conjectural theories tend progressively to come nearer to the truth; that is, to true descriptions of certain facts, or aspects of reality.
(3) But even if we drop all arguments drawn from science, there remain the arguments from language. Any discussion of realism, and especially all arguments against it, have to be formulated in some language. But human language is essentially descriptive (and argumentative),5 and an unambiguous description is always realistic: it is of something - of some state of affairs which may be real or imaginary. Thus if the state of affairs is imaginary, then the description is simply false and its negation is a true description of reality, in Tarski’s sense. This does not logically refute idealism or solipsism; but it makes it at least irrelevant. Rationality, language, description, argument, are all about some reality, and they address themselves to an audience. All this presupposes
realism. Of course, this argument for realism is logically no more conclusive than any other, because I may merely dream that I am using descriptive language and arguments; but this argument for realism is nevertheless strong and rational. It is as strong as reason itself.
(4) To me, idealism appears absurd, for it also implies something like this: that it is my mind which creates this beautiful world. But I know I am not its creator. After all, the famous remark ‘Beauty is in the eye of the beholder5, though perhaps not an utterly stupid remark, means no more than that there is a problem of the appreciation of beauty. I know that the beauty of Rembrandt’s self-portraits is not in my eye, nor that of Bach’s Passions in my ear. On the contrary, I can establish to my satisfaction, by opening and closing my eyes and ears, that my eyes and ears are not good enough to take in all the beauty that is there. Moreover, there are people who are better judges - better able than I to appreciate the beauty of pictures and of music. Denying realism amounts to megalomania (the most widespread occupational disease of the professional philosopher).
(5) Out of many other weighty though inconclusive arguments I wish to mention only one. It is this. If realism is true - more especially, something approaching scientific realism - then the reason for the impossibility of proving it is obvious. The reason is that our subjective knowledge, even perceptual knowledge, consists of dispositions to act, and is thus a kind of tentative adaptation to reality; and that we are searchers, at best, and at any rate fallible. There is no guarantee against error. At the same time, the whole question of the truth and falsity of our opinions and theories clearly becomes pointless if there is no reality, only dreams or illusions.
To sum up, I propose to accept realism as the only sensible hypothesis - as a conjecture to which no sensible alternative has ever been offered. I do not wish to be dogmatic about this issue any more than about any other. But I think I know all the epistemological arguments - they are mainly subjectivist - which have been offered in favour of alternatives to realism, such as positivism, idealism, phenomenalism, phenomenology, and soon, and although I am not an enemy of the discussion of isms in philosophy, I regard all the philosophical arguments which (to my knowledge) have ever been offered in favour of my list of isms as clearly mistaken. Most of them are the result of the mistaken quest for certainty, or for secure foundations on which to build. And all of them are typical philosophers’ mistakes in the worst sense of this term: they are all derivatives of a mistaken though commonsensical theory of knowledge which does not stand up to any serious criticism.
I will conclude what I have to say about realism with the opinion of the two men whom I regard as the greatest of our time: Albert Einstein and Winston Churchill.
‘I do not see’, writes Einstein, ‘any “metaphysical danger” in our acceptance of things - that is, of the objects of physics... together with the spatiotemporal structures which pertain to them.’6 This was Einstein’s opinion after a careful and sympathetic analysis of a brilliant attempt at refuting naive realism due to Bertrand Russell.
Winston Churchill’s views are very characteristic and, I think, a very fair comment on a philosophy which may since have changed its colours, crossing the floor of the house from idealism to realism, but which remains as pointless as ever it was: ‘Some of my cousins who had the great advantage of University education’, Churchill writes, ‘used to tease me with arguments to prove that nothing has any existence except what we think of it...’ He continues:7
I always rested upon the following argument which I devised for myself many years ago... [Here] is this great sun standing apparently on no better foundation than our physical senses. But happily there is a method, apart altogether from our
physical senses, of testing the reality of the sun____astronomers
... predict by [mathematics and] pure reason that a black spot will pass across the sun on a certain day. You... look, and your sense of sight immediately tells you that their calculations are vindicated. ... We have taken what is called in military map-making ‘a cross bearing. We have got independent testimony to the reality of the sun. When my metaphysical friends tell me that the data on which the astronomers made their calculations... were necessarily obtained originally through the evidence of their senses, I say ‘No\ They might, in theory at any rate, be obtained by automatic calculating-machines set in motion by the light falling
upon them without admixture of the human senses at any stage. ... I ... reaffirm with emphasis ... that the sun is real, and also that it is hot - in fact as hot as Hell, and that if the metaphysicians doubt it they should go there and see.
I may perhaps add that I regard Churchill’s argument, especially the important passages which I have put in italics, not only as a valid criticism of the idealistic and subjectivistic arguments, but as the philosophically soundest and most ingenious argument against subjectivist epistemology that I know. I am not aware of any philosopher who has not ignored this argument (apart from some of my students whose attention I have drawn to it). The argument is highly original; first published in 1930 it is one of the earliest philosophical arguments making use of the possibility of automatic observatories and calculating machines (programmed by Newtonian theory). And yet, forty years after its publication, Winston Churchill is still quite unknown as an epistemologist: his name does not appear in any of the many anthologies on epistemology, and it is also missing even from the Encyclopedia of Philosophy.
Of course Churchill’s argument is merely an excellent refutation of the specious arguments of the subjectivists: he does not prove realism. For the idealist can always argue that he is dreaming the debate, with calculating machines and all. Yet I regard this argument as silly, because of its universal applicability. At any rate, until some philosopher should produce some entirely new argument, I suggest that subjectivism and idealism may in future be ignored.
I
In this paper I speak as an amateur, as a lover of the beautiful story of the Presocratics. I am not a specialist or an expert: I am completely out of my depth when an expert begins to argue which words or phrases Heraclitus might, and which he could not possibly, have used. Yet when some expert replaces a beautiful story, based on the oldest texts we possess, by one which - to me at any rate - no longer makes any sense, then I feel that even an amateur may stand up and defend an old tradition. Thus I will at least look into the expert’s arguments, and examine their consistency. This seems a harmless occupation to indulge in; and if an expert or anybody else should take the trouble to refute my criticism I shall be pleased and honoured.1
I shall be concerned with the cosmological theories of the Presocratics, but only to the extent to which they bear upon the development of the problem of change, as I call it, and only to the extent to which they are needed for understanding the approach of the Presocratic philosophers to the problem of knowledge - their practical as well as their theoretical approach. For it is of considerable interest to see how their practice as well as their theory of knowledge is connected with the cosmological and theological questions which they posed to themselves. Theirs was not a theory of knowledge that began with the question, ‘How do I know that this is an orange?’ or, ‘How do I know that the object I am now perceiving is an orange?’ Their theory of knowledge started from problems such as, ‘How do we know that the world is made of water?’ or, ‘How do we know that the world is full of gods?’ or, ‘How can we know anything about the gods?’
There is a widespread belief, somewhat remotely due, I think, to the influence of Francis Bacon, that one should study the problems of the theory of knowledge in connection with our knowledge of an orange rather than our knowledge of the cosmos. I dissent from this belief, and it is one of the main purposes of my paper to convey to you some of my reasons for dissenting. At any rate it is good to remember from time to time that our Western science - and there seems to be no other - did not start with collecting observations of oranges, but with bold theories about the world.
n
i
Traditional empiricist epistemology and the traditional historiography of science are both deeply influenced by the Baconian myth that all science starts from observation and then slowly and cautiously proceeds to theories. That the facts are very different can be learnt from studying the early Presocratics. Here we find bold and fascinating ideas, some of which are strange and even staggering anticipations of modem results, while many others are wide of the mark, from our modem point of view; but most of them, and the best of them, have nothing to do with observation. Take for example some of the theories about the shape and position of the earth. Thales said, we are told, ‘that the earth is supported by water on which it rides like a ship, and when we say that there is an earthquake, then the earth is being shaken by the movement of the water’. No doubt Thales had observed earthquakes as well as the rolling of a ship before he arrived at his theory. But the point of his theory was to explain the support or suspension of the earth, and also earthquakes, by the conjecture that the earth floats on water; and for this conjecture (which so strangely anticipates the modem theory of continental drift) he could have had no basis in his observations.
We must not forget that the function of the Baconian myth is to explain why scientific statements are true, by pointing out that observation is the 'true source’ of our scientific knowledge. Once we realize that all scientific statements are hypotheses, or guesses, or conjectures, and that the vast majority of these conjectures (including Bacon’s own) have turned out to be false, the Baconian myth becomes irrelevant. For it is pointless to argue that the conjectures of science - those which have proved to be false as well as those which are still accepted - all start from observation.
However this may be, Thales’s beautiful theory of the support or suspension of the earth and of earthquakes, though in no sense based upon observation, is at least inspired by an empirical or observational analogy. But even this is no longer true of the theory proposed by Thales’s great pupil, Anaximander. Anaximander’s theory of the suspension of the earth is still highly intuitive, but it no longer uses observational analogies. In fact it may be described as counterobservational. According to Anaximander’s theory, The earth ... is held up by nothing, but remains stationary owing to the fact that it is equally distant from all other things. Its shape is ... like that of a drum. ... We walk on one of its flat surfaces, while the other is on the opposite side.’ The drum, of course, is an observational analogy. But the idea of the earth’s free suspension in space, and the explanation of its stability, have no analogy whatever in the whole field of observable facts.
In my opinion this idea of Anaximander’s is one of the boldest, most revolutionary, and most portentous ideas in the whole history of human thought. It made possible the theories of Aristarchus and Copernicus. But the step taken by Anaximander was even more difficult and audacious than the one taken by Aristarchus and Copernicus. To envisage the earth as freely poised in midspace, and to say ‘that it remains motionless because of its equidistance or equilibrium’ (as Aristotle paraphrases Anaximander), is to anticipate to some extent even Newton’s idea of immaterial and invisible gravitational forces.2
How did Anaximander arrive at this remarkable theory? Certainly not by observation but by reasoning. His theory is an attempt to solve one of the problems to which his teacher and kinsman Thales, the founder of the Milesian or Ionian School, had offered a solution before him. I therefore conjecture that Anaximander arrived at his theory by criticizing Thales’s theory. This conjecture can be supported, I believe, by a consideration of the structure of Anaximander’s theory.
Anaximander is likely to have argued against Thales’s theory (according to which the earth was floating on water) on the following lines. Thales’s theory is a specimen of a type of theory which if consistently developed would lead to an infinite regress. If we explain the stable position of the earth by the assumption that it is supported by water - that it is floating on the ocean (<okeanos) - should we not have to explain the stable position of the ocean by an analogous hypothesis? But this would mean looking for a support for the ocean, and then for a support for this support. This method of explanation is unsatisfactory: first, because we solve our problem by creating an exactly analogous one; and also for the less formal and more intuitive reason that in any such system of supports or props failure to secure any one of the lower props must lead to the collapse of the whole edifice.
From this we see intuitively that the stability of the world cannot be secured by a system of supports or props. Instead Anaximander appeals to the internal or structural symmetry of the world, which ensures that there is no preferred direction in which a collapse can take place. He applies the principle that where there are no differences there can be no change. In this way he explains the stability of the earth by the equality of its distances from all other things.
This, it seems, was Anaximander’s argument. It is important to realize that it abolishes, even though not quite consciously perhaps, and not quite consistently, the idea of an absolute direction - the absolute sense of ‘upwards’ and ‘downwards’. This is not only contrary to all experience but notoriously difficult to grasp. Anaximenes ignored it, it seems, and even Anaximander himself did not grasp it completely. For the idea of an equal distance from all other things should have led him to the theory that the earth has the shape of a globe. Instead he believed that it had the shape of a drum, with an upper and a lower flat surface. Yet it looks as if the remark, ‘We walk on one of its flat surfaces, while the other is on the opposite side’, contained a hint that there was no absolute upper surface, but that on the contrary the surface on which we happened to walk was the one we might call the upper.
What prevented Anaximander from arriving at the theory that the earth was a globe rather than a drum? There can be little doubt:
it was observational experience which taught him that the surface of the earth was, by and large, flat. Thus it was a speculative and critical argument, the abstract critical discussion of Thales’s theory, which almost led him to the true theory of the shape of the earth; and it was observational experience which led him astray.
IV
There is an obvious objection to Anaximander’s theory of symmetry, according to which the earth is equally distant from all other things. The asymmetry of the universe can be easily seen from the existence of sun and moon, and especially from the fact that sun and moon are sometimes not far distant from each other, so that they are on the same side of the earth, while there is nothing on the other side to balance them. It appears that Anaximander met this objection by another bold theory - his theory of the hidden nature of the sun, the moon, and the other heavenly bodies.
He envisages the rims of two huge chariot wheels rotating round the earth, one twenty seven times the size of the earth, the other eighteen times its size. Each of these rims or circular pipes is filled with fire, and each has a breathing hole through which the fire is visible. These holes we call the sun and the moon respectively. The rest of the wheel is invisible, presumably because it is dark (or misty) and far away. The fixed stars (and presumably the planets) are also holes on wheels which are nearer to the earth than the wheels of the sun and the moon. The wheels of the fixed stars rotate on a common axis (which we now call the axis of the earth) and together they form a sphere round the earth, so the postulate of equal distance from the earth is (roughly) satisfied. This makes Anaximander also a founder of the theory of the spheres ,3
v
There can be no doubt whatever that Anaximander’s theories are critical and speculative rather than empirical: and considered as approaches to truth his critical and abstract speculations served him better than observational experience or analogy.
But, a follower of Bacon may reply, this is precisely why Anaximander was not a scientist. This is precisely why we speak of early Greek philosophy rather than of early Greek science. Philosophy is speculative: everybody knows this. And as everybody knows, science begins only when the speculative method is replaced by the observational method, and when deduction is replaced by induction.
Yet there is the most perfect possible continuity of thought between the theories of the Presocratics and the later developments in physics. Whether they are called philosophers, or pre-scientists, or scientists, matters very little, I think. But I do assert that Anaximander’s theory cleared the way for the theories of Aristarchus, Copernicus, Kepler, and Galileo. It is not that he merely ‘influenced’ these later thinkers; ‘influence’ is a very superficial category [see also p.61 above]. I would rather put it like this: Anaximander’s achievement is valuable in itself, like a work of art. Besides, his achievement made other achievements possible, among them those of the great scientists mentioned.
But are not Anaximander’s theories false, and therefore non-scientific? They are false, I admit; but so are many theories, based upon countless experiments, which modem science accepted until recently, and whose scientific character nobody would dream of denying, even though they are now believed to be false. (An example is the theory that the typical chemical properties of hydrogen belong only to one kind of atom - the lightest of all
r
atoms.) There were historians of science who tended to regard as unscientific (or even as superstitious) any view no longer accepted at the time they were writing; but this is an untenable attitude. A false theory may be as great an achievement as a true one. And many false theories have been more helpful in our search for truth than some less interesting theories which are still accepted. For false theories can be helpful in many ways; they may for example suggest some more or less radical modifications, and they may stimulate criticism. Thus Thales’s theory that the earth floats on water re-appeared in a modified form in Anaximenes, and in more recent times in the form of Wegener’s theory of continental drift. How Thales’s theory stimulated Anaximander’s criticism has been shown already.
Anaximander’s theory, similarly, suggested a modified theory -the theory of an earth globe, freely poised in the centre of the universe, and surrounded by spheres on which heavenly bodies were mounted. And by stimulating criticism it also led to the theory that the moon shines by reflecting light; to the Pythagorean theory of a central fire; and ultimately to the heliocentric world system of Aristarchus and Copernicus.
VI
I believe that the Milesians, like their oriental predecessors who took the world for a tent, envisaged the world as a kind of house, the home of all creatures - our home. Thus there was no need to ask what it was for. But there was a real need to inquire into its architecture. The questions of its structure, its groundplan, and its building material, constitute the three main problems of Milesian cosmology. There is also a speculative interest in its origin, the question of cosmogony. It seems to me that the cosmological interest of the Milesians far exceeded their cosmo-gonical interest, especially if we consider the strong cosmogonical tradition, and the almost irresistible tendency to describe a thing by describing how it has been made, and thus to present a cosmological account in a cosmogonical form. The cosmological interest must be very strong, as compared with the cosmogonical one, if the presentation of a cosmological theory is even partially free from these cosmogonical trappings.
I believe that it was Thales who first discussed the architecture of the cosmos - its structure, groundplan, and building material. In Anaximander we find answers to all three questions. I have briefly mentioned his answer to the question of structure. As to the question of the groundplan of the world, he studied and expounded this too, as indicated by the tradition that he drew the first map of the world. And of course he had a theory about its building material - the ‘endless’ or ‘boundless’ or ‘unbounded’ or ‘unformed’ - the ‘apeiron'.
In Anaximander’s world all kinds of changes were going on. There was a fire which needed air and breathing holes, and these were at times blocked up (‘obstructed’), so that the fire was smothered:4 this was his theory of eclipses, and of the phases of the moon. There were winds, which were responsible for the changing weather. And there were the vapours, resulting from the drying
up of water and air, which were the cause of the winds and of the ‘turnings’ of the sun (the solstices) and of the moon.
We have here the first hint of what was soon to come: of the general problem of change, which became the central problem of Greek cosmology, and which ultimately led, with Leucippus and Democritus, to a general theory of change that was accepted by modem science almost up to the beginning of the twentieth century. (It was given up only with the breakdown of Maxwell’s models of the ether, an historic event that was little noticed before
1905.)
This general problem of change is a philosophical problem; indeed in the hands of Parmenides and Zeno it almost turns into a logical one. How is change possible - logically possible, that is? How can a thing change, without losing its identity? If it remains the same, it does not change; yet if it loses its identity, then it is no longer that thing which has changed.
vn
The exciting story of the development of the problem of change appears to me in danger of being completely buried under the mounting heap of the minutiae of textual criticism. The story cannot, of course, be fully told in one short paper, and still less in one of its many sections. But in briefest outline, it is this.
For Anaximander, our own world, our own cosmic edifice, was only one of an infinity of worlds - an infinity without bounds in space and time. This system of worlds was eternal, and so was motion. There was thus no need to explain motion, no need to offer a general theory of change (in the sense in which we shall find a general problem and a general theory of change in Heraclitus; see below). But there was a need to explain the well-known changes occurring in our world. The most obvious changes - the changes of day and night, of winds and of weather, of the seasons, from sowing to harvesting, and of the growth of plants and animals and men - all were connected with the contrast of temperatures, with the opposition between the hot and the cold, and with that between the dry and the wet. ‘Living creatures came into being from moisture evaporated by the sun’, we are told; and the hot and the cold also administer to the genesis of our own world edifice. The
hot and the cold were also responsible for the vapours and winds which in their turn were conceived as the agents of almost all other changes.
Anaximenes, a pupil of Anaximander and his successor, developed these ideas in much detail. Like Anaximander he was interested in the oppositions of the hot and the cold and of the moist and the dry, and he explained the transitions between these opposites by a theory of condensation and rarefaction. Like Anaximander he believed in eternal motion and in the action of the winds; and it seems not unlikely that one of the two main points in which he deviated from Anaximander was reached by a criticism of the idea that what was completely boundless and formless (the apeiron) could yet be in motion. At any rate, he replaced the apeiron by air - something that was almost boundless and formless, and yet, according to Anaximander’s old theory of vapours, not only capable of motion, but the main agent of motion and change. A similar unification of ideas was achieved by Anaximenes’s theory that ‘the sun consists of earth, and that it gets very hot owing to the rapidity of its motion’. The replacement of the more abstract theory of the unbounded apeiron by the less abstract and more commonsense theory of air is matched by the replacement of Anaximander’s bold theory of the stability of the earth by the more commonsense idea that the earth’s ‘flatness is responsible for its stability; for it. ... covers like a lid the air beneath it’. Thus the earth rides on air as the lid of a pot may ride on steam, or as a ship may ride on water; Thales’s question and Thales’s answer are both re-instituted, and Anaximander’s epochmaking argument is not understood. Anaximenes is an eclectic, a systematizer, an empiricist, a man of common sense. Of the three great Milesians he is least productive of revolutionary new ideas; he is the least philosophically minded.
The three Milesians all looked on our world as our home. There was movement, there was change in this home, there were hot and cold, fire and moisture. There was a fire in the hearth, and on it a kettle with water. The house was exposed to the winds, and a bit draughty, to be sure; but it was home, and it meant security and stability of a sort. But for Heraclitus the house was on fire.
There was no stability left in the world of Heraclitus. ‘Everthing is in flux, and nothing is at rest.’ Everything is in flux, even the
beams, the timber, the building material of which the world is made: earth and rocks, or the bronze of a cauldron - they are all in flux. The beams are rotting, the earth is washed away and blown away, the very rocks split and wither, the bronze cauldron turns into green patina, or into verdigris: ‘All things are in motion all the time, even though ... this escapes our senses’, as Aristotle expressed it. Those who do not know and do not think believe that only the fuel is burned, while the bowl in which it burns remains unchanged;5 for we do not see the bowl burning. And yet it burns; it is eaten up by the fire it holds. We do not see our children grow up, and change, and grow old, but they do.
Thus there are no solid bodies. Things are not really things, they are processes, they are in flux. They are like fire, like a flame which, though it may have a definite shape, is a process, a stream of matter, a river. All things are flames: fire is the very building material of our world; and the apparent stability of things is merely due to the laws, the measures, which the processes in our world are subject to.
This, I believe, is Heraclitus’s story; it is his ‘message’, the ‘true word’ (the logos), to which we ought to listen: ‘Listening not to me but to the true account, it is wise to admit that all things are one’: they are ‘an everlasting fire, flaring up in measures, and dying down in measures’.
I know very well that the traditional interpretation of Heraclitus’s philosophy here restated is not generally accepted at
.
present. But the critics have put nothing in its place - nothing, that is, of philosophical interest.6 Here I wish only to stress that Heraclitus’s philosophy, by appealing to thought, to the word, to argument, to reason, and by pointing out that we are living in a world of things whose changes escape our senses, though we know that they do change, created two new problems - the problem of change and the problem of knowledge. These problems were the more urgent as his own account of change was difficult to understand. But this, I believe, is due to the fact that he saw more clearly than his predecessors the difficulties that were involved in the very idea of change.
For all change is the change of something: change presupposes something that changes. And it presupposes that, while changing, this something must remain the same. We may say that a green leaf
changes when it turns brown; but we do not say that the green leaf changes when we substitute for it a brown leaf. It is essential to the idea of change that the thing which changes retains its identity while changing. And yet it must become something else: it was green, and it becomes brown; it was moist, and it becomes dry; it was hot, and it becomes cold.
Thus every change is the transition of a thing into something with, in a way, opposite qualities (as Anaximander and Anaximenes had seen). And yet, while changing, the changing thing must remain identical with itself.
This is the problem of change. It led Heraclitus to a theory which (partly anticipating Parmenides) distinguishes between reality and appearance. ‘The real nature of things loves to hide itself. An unapparent harmony is stronger than the apparent one.’ Things are in appearance (and for us) opposites, but in truth (and for God) they are the same.7
Life and death, being awake and being asleep, youth and old age, all these are the same ... for the one turned round is the other and the other turned round is the first.... The path that leads up and the path that leads down are the same path. ... Good and bad are identical.... For God all things are beautiful and good and just, but men assume some things to be unjust, and others to be just. ... It is not in the nature or character of man to possess true knowledge, though it is in the divine nature.
Thus in truth (and for God) the opposites are identical; it is only to man that they appear as non-identical. And all things are one - they are all part of the process of the world, the everlasting fire.
This theory of change appeals to the ‘true word’, to the logos, to reason; nothing is more real for Heraclitus than change. Yet his doctrine of the oneness of the world, of the identity of opposites, and of appearance and reality threatens his doctrine of the reality of change.
For change is the transition from one opposite to the other. Thus if in truth the opposites are identical, though they appear different,
then change itself might be only apparent. If in truth, and for God, all things are one, there might, in truth, be no change.
This consequence was drawn by Parmenides, the pupil (pace Burnet and others) of the monotheist Xenophanes, who said of the one God: ‘He always remains in the same place, never moving. It is not fitting that He should go to different places at different times.
... He is in no way similar to mortal men, neither in body nor in thought.’8
Xenophanes’s pupil Parmenides taught that the real world was one, and that it always remained in the same place, never moving. It was not fitting that it should go to different places at different times. It was in no way similar to what it appeared to be to mortal men. The world was one, an undivided whole, without parts, homogeneous and motionless: motion was impossible in such a world. In truth there was no change. The world of change was an illusion.
Parmenides based this theory of an unchanging reality on something like a logical proof; a proof which can be presented as proceeding from the single premiss, ‘What is not is not’. From this we can derive that the nothing - that which is not - does not exist; a result which Parmenides interprets to mean that the void does not exist. Thus the world is full: it consists of one undivided block, since any division into parts could only be due to separation of the parts by the void. (This is ‘the well-rounded truth’ which the goddess revealed to Parmenides.) In this full world there is no room for motion.
Only the delusi belief in the reality of opposites - the belief that not only what is exists but also what is not - leads to the illusion of a world of change.
Parmenides’s theory may be described as the first hypothetico-deductive theory of the world. The atomists took it as such; and they asserted that it was refuted by experience, since motion does exist. Accepting the formal validity of Parmenides’s argument, they inferred from the falsity of his conclusion the falsity of his premiss. But this meant that the nothing - the void, or empty space - existed. Consequently there was now no need to assume that ‘what is’ - the full, that which fills some space - had no parts; for its parts could now be separated by the void. Thus there are many parts, each of which is ‘full’: there are full particles in the world,
separated by empty space, and able to move in empty space, each of them being ‘full’, undivided, indivisible, and unchanging. Thus what exist are atoms and the void. In this way the atomists arrived at a theory of change - a theory that dominated scientific thought until 1900. It is the theory that all change, and especially all qualitative change, has to be explained by the spatial movement of unchanging bits of matter - by atoms moving in the void.
The next great step in our cosmology and the theory of change was made when Maxwell, developing certain ideas of Faraday’s, replaced this theory by a theory of changing intensities of fields.