Lecture 1: The Nature of Belief
1.1 Introduction
The subject of science and belief is so vast that it is difficult to know where to begin, so we follow the traditional Oxford advice: start at the beginning, go on until you reach the end, and then stop. But where is the beginning? There are three possibilities:
1. The absolute beginning, before the Creation: "In the beginning was the Word, and the Word was God. All things were made by Him, and without Him was made nothing that was made. His light was the light of men, and the light shone in the darkness, and the darkness did not comprehend it."
2. The beginning of the universe, after its Creation. The big bang, the formation of radiation, matter and the elements, and eventually human history.
3. The beginning of knowledge for each one of us. How do we come to know and to believe?
If we followed the chronological order, we would be talking about science and belief before we considered how we can know anything at all. We will therefore start with the fundamental question of how each individual learns, and how eventually we have come to learn about God and about the development of the universe and the human race through the ages.
1.2 What are we talking about?
Before actually beginning, it is useful to think about what we mean by science and belief, and what sort of questions we will try to answer.
At the crudest level, it represents a dichotomy between reliable, well-grounded and verifiable knowledge on the one hand, and uncertain, unverifiable fancies on the other. More briefly, it is fact versus fif (funny internal feeling). The scientists, we are told, are extremely careful to check all their measurements and theories, and so what they say is reliable knowledge. As for belief, and usually what is meant is religious belief, it is just a matter of feeling; one person feels one thing and another person another thing, and there is nothing to choose between them.
Our main task is to take this apart, and see to what extent it is justified. Up our world-picture. But then what is the connection between our construction and reality? Already we have got ourselves into a tangle that lies at the very heart of epistemology. It is a critical watershed: make the wrong move here and the whole of our philosophy is fatally flawed.
The crucial question is whether we take as fundamental our mind or external reality directly perceived by the mind. If we make the former choice we can never escape from the mind itself; that was the fatal mistake of Descartes, Kant and many other philosophers that led inexorably to the sterile wastes of positivism.
The other road is to recognise that we have to capacity to grasp the external world directly. We know, definitely and without possibility of error, what is directly in front of us. If we are willing to accept this, we have a sound basis for knowledge.
We may well reflect that this seems quite obvious, and only philosophers worry about justifying such things. Indeed, we must make this step before we can even talk about the mind and sense impressions and so acquire the concepts that we used to argue for the alternative approach.
With that essential foundation firmly in place, we can go on to explore in more detail just how we come to know things.
The Epistemic Cycle
If we watch a baby we do not see it sitting still, receiving sense impressions and trying to organise them into a coherent whole. On the contrary, the baby interacts with its surrounding. It stretches out towards things, picks them up, shakes them and throws them down. It becomes aware of its own body: it sucks its fingers and its toes, and thus builds up its knowledge of the world. The baby is active and not passive. This tells us that the way to learn about the world is to act on it and see what happens. "Children are innate scientists, probing, pottering, experimenting with the possible and impossible in a confused local universe. Children and scientists share an outlook on life: 'If I do this, what will happen?' is both the motto of the child at play and the defining refrain of the physical scientist," (Genius: Richard Feynman and Modern Physics, by James Gleick).
As time goes on, the baby builds up its knowledge of a range of familiar objects, and so learns to recognise them on sight, without going through the whole process again. It may be occasionally mistaken, but learns how to correct its error by further interactions with the object. An adult is seldom deceived, except perhaps by artifacts deliberately designed to mislead.
We can gain further insight into what is going on from the experiences of people who have worked on pattern recognition. This research tries to understand how the brain works by building a robot controlled by a computer that is programmed to recognise objects. At the beginning, the field of vision consists of various lines and curves, with different colours. There are so many possible interpretations that it is impossible for even the fastest computer to scan them all. The situation is made much easier if the computer can begin by making some reasonable assumption about the object, and then seeing if its consequences accord with the observations. It can look at it from a different angle, can try to move it and so on. From a simple hypothesis made at the first stage the computer can predict how the picture will change if this is done, and then see if this is correct. This feedback very rapidly reduces the number of possibilities so that by repeating the process it now becomes possible to recognise objects relatively quickly. This cycle of guessing followed by checking and then another round of guessing and checking is called the epistemic cycle.
It is possible that after some time the cycle runs into a dead end; it is clearly not correct and yet it is not obvious how it should be changed. It may then be necessary to go back several stages in the cycle, and try again. It is a requirement of a successful concept of the object that it will eventually be reached from a large number of different starting points. It is a very flexible and ultimately stable process.
This has important philosophical implications, and provides the justification for the starting point already affirmed, namely that the mind directly apprehends an objective external world.
First there is the problem of innate ideas. Are we born with some ideas about the world? If so, is there any reason why they should be correct? If they are not correct, will they not irretrievably distort all subsequent knowledge? On the other hand, if we do not have some innate ideas about the world, how can we ever get started?
These difficulties are overcome by the extreme flexibility and self-correcting nature of the epistemic cycle. Almost any idea, however wrong-headed, suffices to get the cycle going, and once it is going the erroneous elements will soon be eliminated. The cycle can be started anywhere, and it will in the end lead to the same result. It does not even matter in a fundamental way how the cycle is operated; because of its self-correcting nature almost random actions will in the end lead to the same result, although of course that will take longer than intelligent and coordinated actions. Thus it does not matter whether we have innate ideas or not, or what they are. As long as we have the urge to learn by interacting with the world we are set on a process of continual learning that automatically progresses to higher and higher levels.
At the lowest level, the baby learns that there are certain objects in the world with particular properties. His rattle makes a nice noise, it can be thrown about but is not good to eat. Then maybe he is given another rattle of a different shape and colour. He recognises that the two rattles have some properties in common but in other ways they are different. He realises that he can think about rattles in general, abstracting from any particular rattle. In this way he has formed the concept of rattle. He will make mistakes; perhaps he sees something that looks like his rattle, but when he shakes it nothing happens; it is not a rattle but another sort of toy. In this way the baby builds up a series of concepts that enables him to classify the objects and the people around him.
This process goes on as the baby grows up, through higher and higher epistemic cycles. Very soon, particularly as the ability to speak develops, the process becomes a social one. He learns the word for rattle, and indeed the development of the concept of rattle is helped and crystallised by the word. Our language develops in response to our apprehension of reality. Concepts are developed and refined as the learning process proceeds; the concept of swan is revised when we sees one that is black.
This process is not without its dangers, particularly if we come to believe that there is a one-to-one correspondence between language and reality. This is not so bad for simple objects, although some languages are richer than others; Eskimo has about thirty words for different types of snow. The danger becomes acute at the higher levels of abstraction, when we use words like mind, space and time. Such words have a long history and do not have sharp and easily defined meanings, but are only defined in the context of definite philosophical or scientific beliefs.
Perhaps the baby eventually becomes a scientist or a theologian, and then he or she is embarked on further voyages of discovery, to higher and higher levels of abstraction.
This process is never-ending, as we explore the richness and complexity of reality. We can be sure of some of our knowledge, but there are also legitimate areas of disagreement. A concept or a scientific theory may have been quite well tested against a range of experiences but may later on fail, and then we have to think again. The whole process also presupposes a willingness to revise our ideas in the face of contrary evidence. If we stick to our beliefs regardless, the whole fruitful growth of our knowledge is impossible. It is not surprising that there are still strong areas of disagreement, but we have available the means to resolve them.
The concept of epistemic cycles applies at every level of knowledge: from the initial efforts of the child to the work of the scientist, philosopher and theologian. While ultimately the process leads to the attainment of objective truth, it becomes progressively more difficult with the degree of abstraction of the subject matter. The child soon finds out if he is mistaken, and the scientist can subject his theories to sharp tests, often requiring precise numerical agreement. If a philosopher makes a false move, all his system is fatally flawed, and in the end will prove untenable, but in the absence of sharp tests it may be a long time before this is apparent. The system may have much to commend it, and when the first difficulties appear it may be possible to develop the system to account for them, thus postponing the final reckoning. This is still more true for systems of religious belief, which can survive for millennia. The final challenge comes partly from within, but more often from without, as another system of beliefs proves able to account for all that is good in the original system, and much else besides. Individuals may find it very difficult to change, but the next generation is able to take a more objective view and so eventually the old beliefs die away and become a historical memory.
It is important to recognise that throughout this account we have tacitly presupposed that we live in a real world. This is the essential assumption underlying the epistemic cycle, for it describes our interaction with reality. It is justified by the result. If there were no objective reality the cycle would not work, still less would it yield results that are agreed among many people. If we were trapped in our own minds, building concepts and ideas into acceptable patterns, there would be no reason why my pattern should be any truer than yours. Indeed I would have no reason to even speak about you, for the concept of another person would on this view be simply yet another construction of my own mind. I am trapped within my own self, a solipsist. The epistemic cycle would not work because there would be no objective standard that would enable us to distinguish the false from the true. Its success would be wholly inexplicable; if there is no objective external world then why can we improve our ideas by systematically correcting our mistakes?
Scientists know all this instinctively, although so deeply that it is almost never articulated. Scientists are natural and instinctive realists, and always behave in a realist way, even though they may use philosophical concepts of different types to talk about their work.
As an example, we can quote the opening words of Duhem's essay on theoretical physics: "The human mind, being placed in the presence of the external world in order to know it, encounters first of all the realm of facts," (Uneasy Genius, p. 320). He saw clearly that philosophical doubt and skepticism serve only to erode our capacity to grasp reality. We can even use concepts such as body, extension, time and motion in our attempts to understand the world, without any preliminary philosophical analysis. We do not of course understand them with any precision, but in a way that is sufficient for us to begin scientific work.
The recognition of individual facts is but the first step in knowledge, the second is the classification of facts, the recognition of the general in the particular. This is a spontaneous unconscious act, a basic characteristic of human thinking. It is not an inference from sensations; it is the immediate grasping by the mind of a facet of reality.
1.3 The Beginning of Human History
With our basic philosophical foundation in place, we can begin our study of how the human race came to know and to believe. We begin at the beginning, on the African savannah where early man emerged from the forests and started to live on the plains. It was not an easy transition; they were beset with wild beasts and had to search for their food, but somehow they made it. It is only during the present century that the fossilised remains of early man have been found in various sites in Africa, mainly in the Great Rift Valley that cuts Africa in two from north to south. The first discoveries were made by Louis and Mary Leakey in the Olduvai gorge on the Serengeti Plain, and later by Dart at Sterkfontein near Johannesburg that I have visited. Most of the findings were of skulls, that are most easily preserved, but in some cases much of the skeleton has been found as well.
Similar remains were found in many other parts of the world, in Java by Dubois and in China by Teilhard de Chardin at a site near Peking that I have also visited. Many remains of early man have been found in Europe, that of Neanderthal man being the most familiar.
By examining the sites where these remains are found we can reconstruct to some extent the lifestyle of early man. From the surrounding animal bones we can determine his diet, and from the stone axes and other tools we can understand how they killed their prey and prepared it to be eaten. We can classify the skulls and try to reconstruct the lines of descent from one type of man to another. This is now greatly helped by modern dating techniques, both radiochemical and biochemical. We now know that early forms of hominids were found about five million years ago, and homo sapiens using stone tools about two million years ago.
But what went on in those ancient skulls? That is the question that we would like to answer. Were they men and women with much the same mental equipment as our own, or were they little more than apes, with a few faint glimmering of intelligence that would develop slowly over the millennia? We can learn a little from their burial customs. If they buried weapons and cooking pots with their dead, it may be conjectured that they believed in some sort of after life.
The most familiar indication of the mentality of early man was found in the caves of Lascaux, Altimira and other sites. We are familiar with the strikingly realistic pictures of horses and cows and bulls painted with great artistic skill on the walls of the caves. It has been conjectured that these are connected with religious ceremonies performed before or after hunting the animals depicted. Whatever their meaning, "they were drawn or painted not only by a man, but by an artist . . . Monkeys did not begin pictures and men finish them. Pithecanthropus did not draw a reindeer badly and Homo Sapiens draw it well . . . the wild horse was not an Impressionist and the racehorse a Post-Impressionist . . . there is not a shadow of evidence that this thing evolved at all" (Chesterton).
A much less familiar but more striking indication of the mental capacity of early man was found at Ishango in the mountains of central equatorial Africa. There, at a Palaeolithic site, was found a bone tool with engraved marks along the edges. The marks were in groups that suggested that they were not just decoration, but had a definite numerical purpose. These marks were studied in detail by Alexander Marschak, and he concluded that the marks refer to the days in the lunar cycle, and the groups to the phases of the moon.
It did not seem likely that such markings were unique to this particular part of Africa, so he read widely in the literature relating to early man, and looked through collections of artifacts in museums. He found a large number of bones, antlers and stones inscribed with a variety of marks that could be connected in similar ways with the lunar cycles. Such marking are thus an ubiquitous feature of the artifacts of early man.
The marks had of course been noted by other scientists, but they suggested that they were decoration, or perhaps tallies of successes in the hunt. In many cases it is evident that the marks are not decoration because if they were, they would be regular and made at the same time with the same tool, which was not the case for those he studied.
If this interpretation is correct, we see that early man had a considerable degree of natural intelligence, perhaps quite similar to our own. He was a keen observer of nature, and realised that to be useful his observations must be recorded in a systematic way. This is the beginning of language and of the storing of information.
This is something that is quite new on the earth. It is the appearance of a new type of being, completely different from even the most highly-developed animals. There is no trace of a gradual progression from apes to men. Early man could draw very well; apes do not draw at all. Early man recorded the phases of the moon, an activity that has yet to be noted among animals.
Our fragmentary knowledge of the thought of early man may be supplemented by studies of primitive peoples today. We find that "the whole mentality of primitive man is religious. His conception of reality is never limited to what he sees and touches. So far from being a materialist, it is an effort to him to think in terms of matter" (Dawson, Progress and Religion, p.86). Mary Kingsley has remarked from her own experience that "His mind works along the lines that things happen because of the action of spirit upon spirit. We think upon the line that things happen from the action of matter upon matter . . .The Englishman is constrained by circumstances to perceive the existence of an (external) material world. The African regards spirit and matter as undivided in kind, matter being only the extreme low form of spirit" (West African Studies, p. 330). We see how strongly we are conditioned by scientific materialism.
Dawson goes on to remark that "everywhere we find the belief that there exists behind the outward appearance of things a mysterious world of spiritual or supernatural forces, which rule the course of nature and the life of man." These beliefs are often a rich mixture of bizarre stories, but these may conceal underlying monotheism. Chesterton has told the story of a missionary who "was preaching to a very wild tribe of polytheists, who had told him all their polytheistic tales, and telling them in return of the existence of the one good God who is a spirit and judges men by spiritual standards. And there was a sudden buzz of excitement among those stolid barbarians, as at someone who was letting out a secret, and they cried to each another, 'Atahocan. He is speaking of Atahocan!'" (The Everlasting Man, p. 101).
As religious beliefs developed it became necessary to have in each tribe medicine men, shamans, a priestly caste who maintained and passed on the beliefs of the tribe. They were "men set apart from their fellows, relieved from the necessity of labour, that they might devote themselves to the acquisition of knowledge" (Dawson). They had the duty to "know more than their fellows, to acquaint themselves with everything that could aid man in his arduous struggle with nature. The properties of drugs and minerals, the causes of rain and drought, of thunder and lightning, the changes of the seasons, the phases of the moon, the daily and yearly journeys of the Sun, the motions of the stars, the mystery of life, and the mystery of death" (Sir James Frazer, Lectures on the Early History of Kingship, 1905, p. 90).
Thus we find in the mind of primitive man that religious beliefs and knowledge of the world are inseparable, and that it was the first priests who had a professional interest and duty to find out about the world and how it can be controlled. Their work implied the central concepts of objective knowledge of the world and the causal influence of one thing on another. They were the forerunners of the scientists of today.
1.4 Early Civilisations
We must now pass rapidly over many millennia when men and women gradually learned to live together in communities that grew and coalesced to form villages, town and cities. At the same time, the growth of crops and the production of goods became more specialised so that each man and woman had a definite place in society and a range of tasks to perform. We know a great deal about such civilisations. Some, like Sumeria, Babylon and Egypt have long disappeared; others like India and China are still with us, though in a greatly altered form.
These civilisations all developed many of the arts to a high degree, especially architecture and the working of wood, metal and stone. We still marvel at the pyramids of Egypt and the treasure of Tuthankamen. They had priestly castes and well-developed systems of beliefs, but no science as we know it today.
There is one ancient civilisation that stands out above all others because of its high intellectual achievement that it must be considered on its own, namely that of ancient Greece. It is in Greece that we find the beginnings of systematic thought, of philosophy, history, geometry, and rhetoric, as well as the arts of poetry, and drama, and the beginning of science.
1.5 The Greeks
It was the Greeks who developed the art of asking the right questions, which is the essential preliminary to finding the right answers. They wanted to know why things behave as they do and formulated some of the most fundamental scientific questions such as whether matter is discrete or continuous and whether the universe is finite or infinite in space and in time. The great achievement of the Greeks was to put forward the idea of universal causality and to stress that it might be studied by rational argument. This in turn led to the recognition of a higher reality transcending all change and limitation (Dawson). These are major problems that continually recur during the succeeding centuries.
The Greeks were acute observers but they underestimated the value of controlled and specific experiments, and in any case regarded experimentation as a rather menial task beneath the dignity of a philosopher and fit only for slaves. Lacking the right approach, and with no appreciation of the immensity of the task they had set themselves, it is hardly surprising that their answers were frequently vague and naive.
Socrates was always going around asking people what they meant by what they said. Among the questions that exercised the Greeks was why the world behaves as it does. What lies behind the diversity of objects and processes that we see around us? What is the meaning of change? How can we find answers to such questions, what sort of answers are possible and how can we test them? Such questions lie at the heart of science.
Socrates' questioning led to the ideal of a science that makes nature fully intelligible, and by this he meant gaining an insight into the cause and purpose of everything that happens. He was alarmed by the speculations of the atomists that the world is made of atoms and the void, and is ruled by chance. In the words of Whitehead, the world is then just the hurrying of material, endlessly, meaninglessly. This leaves no room for right and wrong, for duty and responsibility. This horrified Socrates, so his aim was to save purpose for man. Now, with the wisdom of hindsight, we can see that physics is not and should not be about purpose, although it is a most purposeful enterprise. The efforts of the Greeks to save purpose for man and for the cosmos had the effect of putting physics into a straightjacket for two thousand years.
The Greeks were particularly concerned with the problems of change and the mathematical structure of the world. They realised that a possible answer to the problem of change is to analyse everything into simple components, each behaving in a simple way that we understand. Then, by combining these components, we may hope to understand more complicated bodies or phenomena. We see changes around us continually, and they are not entirely chaotic but tend to follow definite rules and patterns. What is the unchanging substance and what is the changing element? Thales (c 580 BC) suggested that the universal stuff is water; Anaximenes thought it was air and Heraclitus thought it was fire. A later theory of Anaximander combined these suggestions and postulated four elements, earth, air, fire and water. All bodies are made up of these elements in various proportions, and changes are due to alterations in these proportions. Parmenides analysed the idea of change, pointing out that the fundamental stuff, whatever it is, must itself be unchangeable. Whatever is, is, and whatever is not, is not, eternally. Thus all change is an illusion. This apparently logical but obviously unsatisfactory conclusion stimulated two main sets of theories to avoid the difficulty, the atomism of Democritus and the theory of act and potency of Aristotle.
In his atomic theory, Democritus postulated that all matter consists of different combinations of indivisible atoms moving in a void. These atoms are intrinsically unchangeable, but they move relative to each other and this accounts for the observed changes. Thus Parmenides' argument is essentially accepted, but one type of change, namely local motion, is excluded from his criticism; as it is not a 'thing' it does not have to be unchangeable.
The atomic theory was a valuable insight, but the Greeks had no idea how it could be verified, how big are the atoms, and how they interact with each other. Epicurus also held that the world is made of atoms, but was concerned about preserving freedom and purpose. He suggested that this could be done by allowing each atom to swerve, even rather slightly, from the path predetermined by its nature.
Aristotle developed his more subtle theory of act and potency to answer Parmenides. He said that every thing, or substance, is real in two different senses, actual and potential, the one being what it actually is at the present time and the other being what it could possibly be at another time. Change is then the actualization of a potency by an intrinsic or extrinsic cause.
Neither of these theories received much further development in the Greek period, but both were ultimately of great importance for science and philosophy.
Change can be analysed at the purely physical level of what is actually happening, but also at the level of purpose: who brings the change about, and why? Plato held that the substance is the mathematical form, which imposes order on chaos. Aristotle thought that there are four types of cause: the material, the formal, the efficient and the final. A substance must therefore have other attributes, since geometry gives no knowledge of efficient and final causes.
The other problem studied by the Greeks is the mathematical structure of the world. Pythagoras discovered the numerical relations between the lengths of the strings giving an harmonic chord, and this led him to suggest that whole numbers underlie the rational structure of the world. Numerical relations were widely sought, and there was great consternation when it was found that the length of the diagonal of a square cannot be expressed as an integral fraction. Plato extended the work of Pythagoras and proposed geometry as the basic pattern of the world, and looked for geometrical patterns in nature. This stimulated astronomy and since each fixed star traverses a perfect circle around the pole of the celestial sphere this was assumed to be the natural type of movement of the heavenly bodies. The planets execute more complex paths on the celestial sphere, and Plato's school tried to explain them as the resultants of several circular motions. This in turn stimulated the study of mathematics.
Aristotle accepted this theory and divided the universe into two regions, the celestial and the terrestrial, obeying different laws. Celestial matter, of which the stars and other heavenly bodies are made, is eternal, incorruptible and moves in the most perfect way, which is circular. This explains the apparent motions of the stars, but those of the planets can only be explained as a superposition of several circular motions. All other motions are subject to these cyclic motions; this is the origin of astrology. Terrestrial matter is changeable and corruptible and moves in straight paths. Everything has its natural place, and strives to reach it. Thus fire goes upward and stones fall down towards the centre of the earth. The rate of fall depends on the amount of matter in the falling body. This far-reaching, coherent and plausible synthesis exerted a powerful influence for many centuries, and implanted the conviction that the earth is the unique centre of the universe. It is a well-ordered, easily intelligible world view, sometimes illuminating, sometimes confusing but always dominating (Grant).
Some minor defects appeared quite soon: planets, the sun and the moon vary in apparent size and brightness and so are not always at the same distance from the centre of the earth. The more accurate the observations, the more difficult and complicated it became to account for the motions of the planets by superposing circular motions. Ptolemy worked on this problem and ultimately developed a very complicated system of cycles and epicycles to do this. This and other difficulties tended to be ignored and rejected by the Aristotelians, thus hindering further progress.
The Greeks realised that theories can be divided into two types: those that give a true account of reality and those that merely imply consequences that agree with experiment, without claiming to be a true account of reality. These are the essentialist and the descriptive theories, typified by Aristotle and Ptolemy respectively. The essentialist view is that science achieves a knowledge of the nature or essence (the intelligible principle of unity or activity) of a thing. Our studies give us an insight into the nature of a thing and then we see how its properties follow as a necessary consequence of this. Aristotle recognised the difficulty of attaining such insights, but thought that this was the ideal towards which the ideal science tends. On the other hand the descriptive view is that the aim of science is only to give an account of the observed facts; this is all that can be expected of science, that it shall 'save the appearances' but cannot make any justifiable claim to give an insight into essences.
Plato contrasted the perfect world of ideas or forms and the changing realm of matter. We can try to glimpse the perfect world by studying our imperfect one. The ratios found in musical harmonies provide an example of this.
The nature of motion is the most fundamental problem in all physics and hence lies at the basis of science. All motion, according to Aristotle, is due to the continuing action of a mover, and if the mover stops acting, the motion ceases. We can see this, for example, when a horse pulls a cart. But what about an arrow shot from a bow? After it has left the bow it does not fall immediately to the ground, but continues to move. Aristotle suggested that the air pushed aside by the arrow moves round to the back and impels it forward.
Since all motion is due to the action of a mover, it is indicative of purpose. In animate bodies, such as animals, the soul is the mover, and in the planets a celestial intelligence, with the mover and the moved distinct but inseparable (Grant). We are then led to ask what moved the mover, and so on. An infinite regress is not acceptable, so Aristotle concluded that there must be a Prime Mover, that is not itself moved. This argument was later taken up by Aquinas and used in one of his ways to God.
Both Plato and Aristotle agreed that there is a real world behind what we observe. From our observations we intuit our theories, and for the Greeks a theory is the definition from which all properties can be deduced. Thus we see a triangle and this gives us the idea of a triangle. We then define it, and from the definition we can deduce all its properties.
Behind arguments such as these is the belief that it is possible for the mind to intuit general principles that contain the essence of the object of study, from which all its behaviours can be deduced. If this were true, then basic truths about the world can be attained without detailed observation and experiment. This may work in some simple cases, but in general it is far too easy and superficial a way to try to learn about the real world, and is not the way that science can develop.
Time was also a problem for the Greeks. If all perfect motion is circular, eventually when all the circles have been traversed, the world will come back to the same state as before. Thus we have a cyclic universe that repeats itself periodically. This solution has the merit of solving the problem of an infinite number of different events, which would be entailed by a non-cyclic universe of infinite duration. Such a cyclic universe is however profoundly debilitating; why bother to strive for higher things when it has all happened before, an infinite number of times, even including what we think are our best ideas? This conception of a cyclic universe is found in all ancient cultures, and is the main reason for their failure to develop a viable science.
Cycles were also of great importance in Plato's cosmology. The celestial cycles defined the periods of fertility and health,so it was important that children should be born at propitious times. Such beliefs still survive as astrology. Furthermore, the cosmic process was alternately subject to divine guidance and left on its own, when it soon degenerated into chaos, so that God is opposed by the factors leading to chaos, the rational and the irrational holding sway in turn.
This emphasis on cycles, implying that everything has already happened an infinite number of times, and will recur in the same way, has the effect of weakening our sense of time. There is nothing to distinguish one cycle from another, so there is little meaning to be attached to 'before' and 'after'. Thus Aristotle remarked that probably every art and every philosophy had already reached its maximum development and then perished. This not only discourages effort but also weakens the sense of time, so vital for the growth of science.
Aristotle was an excellent observer and systematiser, and so made outstanding contributions to biology. The concept of purpose is very suitable to described biological development, and he naturally applied this to the inanimate world as well, treating the world as a vast organism. This suggests that Aristotle's success as a biologist is perhaps responsible for his failure as a physicist.
For all its glories, Greek science was still-born; it never developed into a self-sustaining enterprise.
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