Eureka! Page 2

  Two Cultures

  Greek society was affluent enough for some relatively well-to-do people to have sufficient time to consider philosophical questions, including the nature of the world around them. They also had the intellectual freedom to pursue original lines of thought. Significantly, the Greeks had no centralised religion and no official caste of priests. Babylonian society was hierarchical, both in the literal sense that it was ruled by priests (from the Greek hieros, priest, arche, rule) and in the sense that it was rigidly stratified. In Greek society there was tolerance of a wide range of religious views, and of debate in general. An excellent example of this can be found in the views of Xenophanes of Colophon (fl. 520 BC),1 a philosopher and theologian. Xenophanes lived to be at least 92, wrote in verse and travelled extensively. He was particularly critical of popular religion, and of the gods in the epic tales of Homer and Hesiod. He said that:

  Homer and Hesiod have ascribed to the gods all those things which are shameful and reproachful among men: theft, adultery and deceiving each other … Mortals believe that the gods are born, and that they have clothes, speech and bodies similar to their own … If cattle, horses and lions had hands, and could draw with those hands and accomplish the works of men, horses would draw the forms of gods as like horses, and cattle like cattle, and each would make their bodies as each had themselves … The Ethiopians claim their gods are snub-nosed and black, while the Thracians claim theirs have blue eyes and red hair.

  Here I should explain that in the case of some Greek thinkers, notably Plato and Aristotle, we are fortunate enough to have had virtually all of their works preserved intact. With others, particularly the early Greeks, we have very little of their work preserved directly, and we have to use what are known as fragments – quotations from them, or descriptions of their views preserved in the work of later writers. The fragments of Xenophanes are very important. Firstly, Xenophanes was critical of popular religion, without being persecuted for his views. Secondly, his ideas illustrate some important features of the early Greeks. Critical of orthodox opinions, they had a self-awareness that allowed them to see a great deal of traditional religion as anthropomorphic. We see here also the cosmopolitan nature of the Greeks. As a trading and seafaring nation, they were aware of the views of other cultures, and able to take them into account.

  Cosmos: an Elegant Universe

  The ancient Greek word cosmeo has given us several words in modern English, such as ‘cosmology’ (the study of the universe), ‘cosmogony’ (the study of the origins of the cosmos) and ‘cosmetic’. The last may seem somewhat surprising, but cosmeo not only meant to order or arrange, but also had a sense of good order; and also of beautiful, aesthetically pleasing order. A statement which is deceptively simple, but is in fact of enormous importance for the origins of science, is that the Greeks believed themselves to live in a cosmos, a well-ordered place. To them, the universe had an order, and a good and pleasing order at that. What is more, the Greeks were the first to recognise a distinction between the natural and the supernatural. They considered the cosmos to be an entirely natural place. Things did not happen at random, or by the caprice of the gods. With an optimism that was typical of them, the early Greeks believed the cosmos to be comprehensible. The order of the cosmos was something that could be discovered and understood by humans. Furthermore, they believed that the cosmos could be successfully described in words and numbers.

  The first philosophers and scientists were the Milesians: Thales (fl. 585 BC), Anaximander (fl. 555 BC) and Anaximenes (fl. 525 BC). They came from Miletus in Asia Minor (on what is now the Turkish coast), an important cosmopolitan trading centre which had strong links with older Eastern cultures. Thales is said to have predicted an eclipse in 585 BC, to have been a brilliant geometer, and to have allowed a Greek army to cross a river by suggesting that they divert it into two streams, each of which was fordable. Anaximander was a pupil of Thales, and is said to have produced the first map of the known inhabited world. Anaximenes is reputed to have been a pupil of Anaximander. Unfortunately, little else is known about the lives of the Milesians, but they were the first to describe the cosmos in entirely natural terms, and the breadth of their theorising was quite remarkable. They also took the important step of not focusing on individual events (e.g., what caused this earthquake?), but looked instead at classes of events (e.g., what causes earthquakes?). This enabled them to form general theories about the causes of events, rather than specific theories about one event.

  The philosopher Heraclitus of Ephesus (fl. 500 BC) insisted that the cosmos worked according to a logos, which in Greek could mean ‘word’, ‘account’, ‘measure’ or ‘proportion’. We derive the word-ending ‘-ology’ from logos (as in biology), as well as the word ‘logo’. That the cosmos obeyed a logos meant not only that it was an orderly place, but also that it was comprehensible to humans if they could grasp the nature of this logos. The cosmos could be correctly described and understood using words. To do so, it was necessary for humans to generate a common account of the logos, not just individual accounts, and to follow it wherever it led. Thus, the Greeks were happy to pursue all sorts of arguments to their logical conclusion, which was an important factor in driving their theories forward. Heraclitus also said that:

  This cosmos, the same for all, was made by neither god nor man, but was, is and always will be: an ever-living fire, kindling and extinguishing according to measure.

  This expression of the idea of an objective, natural and orderly cosmos was typical of the early Greek scientists. Heraclitus believed that:

  For those who are awake the cosmos is one and common, but those who sleep turn away each into a private world. We should not speak and act like sleeping men.

  This is not to say that either the early Greek philosopher-scientists or the Greek populace were atheists. After all, the Greeks gave us a marvellous theology, full of characterful gods like Zeus and Poseidon. However, there was a huge difference between the sort of gods that societies prior to the Greeks – and the Greek populace – believed in, and the philosopher-scientists’ conception of god. The popular gods had unpredictable wills of their own, and often interfered in human affairs and with the world in general, either deliberately or accidentally. The easy explanation for phenomena such as thunder and lightning was simply to say that they were caused by the gods, perhaps because they were angry with humans, perhaps because they were arguing among themselves. The Milesians refused to use the gods to explain events in this manner. Events in their cosmos had natural causes. If the early scientists believed in gods, then theirs were gods who kept order and did not interfere with the natural processes of the cosmos. It was, of course, important that the philosopher-scientists should be free to have their own conception of god. Xenophanes, free to express his opinions, was not an atheist, but stressed the need for one god who behaved in a seemly manner and did not change his nature.

  The history of ancient Greek science is the history of a relatively small group of people – far, far smaller than the scientific community of today. Their ideas were influential, both historically and in Greek society, but their views need to be distinguished from those of the Greek population as a whole, many of whom still held the old views about the gods and myths. Against that background, it is all the more remarkable that science began to come about at all. The views of the early philosophers were known and discussed in society, and The Clouds, a play by the famous Athenian dramatist Aristophanes (c. 450–385 BC), had philosophers debating whether lightning was caused by the clouds or by the gods.

  Myths and Theories

  There was another critically important distinction between the early Greek philosopher-scientists and their predecessors. This was that they sought to explain the cosmos in terms of theories rather than myths. Again, this is not to say that the Greek populace gave up believing in myths, or that the Greeks did not give us a rich and enduring mythology. Rather, a small group of people began to think in a different way and this was
enormously important for the origins of science. The Babylonians and other societies prior to the Greeks generally used mythopoeic thought – thought expressed in terms of myths and poems. There were significant differences between myths and the sort of theories that the early Greeks were interested in. This allowed the Greeks to begin to make rapid progress in both philosophy and science.

  Think of the different ways in which we compare myths and compare theories. How do we decide if one myth is better than another? There are criteria which might apply to myths, but not the same sort as apply to theories. Rather, they are literary criteria. Myths might be imaginative, entertaining, or carry some message by means of allegory, etc. So one might prefer the gods of Greek myth to the gods of Norse myth, or Tolkein’s The Hobbit to The Lord of the Rings, on grounds of grandeur. Or vice versa. One might prefer simplicity to grandeur. These are subjective, rather than objective, criteria. Do we judge theories in this way? One might also consider this. There are many ways of telling the story of King Arthur. Is there a right way? If we stick to the historical evidence for Arthur, we get a pretty dull story. So we might embroider some mythology around him. But what do we embroider, and on what grounds?

  We can collect evidence and discuss the merits of a theory. We have a good idea of why one theory is better than another. There is a need for theories to be consistent internally, or if we hold a group of theories, for them to be consistent as a group. Theories should also be as general as possible and have no exceptions. So there is a drive to establish a completely general theory. There is no great need for myths to be consistent with themselves or with other myths. Myths are compatible with one another in a way that theories are not. However, if I hold the theory that the sun is made entirely of stone, and you hold that it is made entirely of fire (an issue which concerned the ancient Greeks), then one of us is right and one of us is wrong. Theories exclude other theories from being true in a way in which myths do not.

  Myths ask us to believe in a great number of things, while theories do not. There is an important principle applying to theories, which runs like this: We do not suppose there to be more things in our theories than the bare minimum required to account for the phenomena. This is known as the principle of parsimony, or Ockham’s razor, after the medieval philosopher William of Ockham (c. 1285–1349). For example, we might have two ways of explaining why presents appear on Christmas morning. Is there a Santa Claus with some magic reindeer who delivers presents down the chimney? A delightful piece of mythology, but the more mean-minded of us will say that humans have bought the presents and we have no need to believe in Santa and his reindeer. A good theory is very mean with what it supposes there to be. A myth, on the other hand, may be a good myth because it has more, or more extravagant, magical monsters. The problem is, what criteria do we have for determining how many and what sort of monsters? Ultimately, the difference between myth and theory is this. A good myth may be no nearer the truth, in terms of being a description of the world, than a poor myth. A good theory is.

  Theories can be debated in a way in which myths cannot, because of the objective criteria for theories. We can collect the evidence, debate the merits of competing theories and agree on the best theory. It is by no means clear that one can do something similar with myths. I have no wish to dismiss myths, which are fine examples of human creativity, imagination and ingenuity. Myths have their place, but they also have their limitations. One important limitation is that myths do not generate or drive progress in the way that theories do. The requirements that theories be consistent, that they cover all the evidence and be as general as possible while being as parsimonious as possible, mean that it is clear what form a better theory might take.

  The Greek use of theory can be considered alongside their idea of the cosmos as a well-ordered, natural place. The cosmos was to be explained in terms of theories which used natural explanations only. As Heraclitus insisted, there was a need for an objective account of it. There was a belief that its nature could be described and comprehended by human beings using words and numbers. Once the Greeks formulated the idea of a cosmos, and began to try to explain it in terms of theories, then their science and their philosophy began to progress very rapidly. They made leaps of sophistication in their theories of matter and their cosmology, and many other sciences appeared which were simply not seen in other ancient societies.

  Natural Phenomena

  Do we know that the Babylonians and Egyptians had no theories? We have a considerable amount of evidence about Babylonian astronomy, but we have yet to find any real evidence of a proper theory of the heavens. The ancient Greeks, and in particular Aristotle, were fascinated by theories and wrote down every one they could find. Aristotle’s aim was usually to show these theories to be wrong and himself to be right. If he had known of any Babylonian theory, it is very likely that he would have recorded and criticised it. He was certainly aware of Babylonian and Egyptian culture, and indeed praised the accuracy of their astronomical observations. Yet he tells us that:

  Others state that the earth rests on water. This is the most ancient account we have, which was given by Thales of Miletus, that it stays in place through floating like a piece of wood or something similar … as if the same argument did not apply concerning the water supporting the earth as to the earth itself.

  The point here is not that this theory is right, nor even that it is a particularly good theory. It is that it attempts to explain the world in a certain manner, without resort to myth or poetry. It makes a clear statement about the nature of the earth which can be discussed and verified or falsified. It is a theory, depending on natural things only, and not a myth. It can be sharply contrasted with the Greek myth that the world was supported on the shoulders of Atlas. So too with many other early Greek theories. The later chronicler Aetius tells us that:

  Concerning thunder, lightning, thunderbolts, whirlwinds and typhoons, Anaximander states that all these come about because of wind. Whenever it is enclosed in a thick cloud and then forcibly breaks out, due to its fineness and lightness, then the bursting makes the noise, and the rent against the blackness of the cloud is the lightning flash.

  Again, this may not be the greatest of theories, but it attempts a natural explanation of phenomena that had previously been explained by the actions of the gods. Zeus was supposedly responsible for thunder, Poseidon for earthquakes.

  So the Greeks were responsible for a new conception of nature as a cosmos, and indeed for the very distinction between natural and supernatural. It could even be said that they ‘discovered’ nature. So, too, they were responsible for producing the first theories, devoid of supernatural influences, of how nature might work. They effected the transition from myth to theory. Next we shall see the rapid progress they made with their theories and their idea of a cosmos, as they sought to carry through their vision of a new way to explain the world.

  Footnote

  1 With some of the earlier Greeks, we have only a rough indication of when they did their most important work, rather than specific dates for birth and death; ‘fl.’ (floruit, when they flourished) indicates this date.

  2 The First Scientific Theories

  Which was to be proved.

  Euclid, Elementa, book 1, proposition 5 and passim (usually quoted in Latin: ‘Quod erat demonstrandum’)

  The first ideas about the nature of the world gave a hemispherical picture of the universe. There was the earth, which was flat, and a hemispherical heaven above it. There was no conception of anything beneath the earth (such as the other half of the heavens), and so no question of whether the earth needed some form of support to hold it in position. Thales made a conceptual leap forward in seeing the problem of what might lie below the earth. He gave us the first spherical, as opposed to hemispherical, cosmos. Aristotle’s criticism, doubtless voiced by many others before him, was that water is something we know to be heavy, so why does it not fall as well? The next generation of cosmologies had the earth supported by air
, something which in our experience does not fall. Aristotle tells us that:

  Anaximenes, Anaxagoras and Democritus say that it is the flatness of the earth that is the reason why it stays still, for it does not cut the air below but covers it as flat bodies are able to do.

  So the earth rides on air, a bit like a frisbee. For us today, these theories seem slightly odd, but the resources available to the Greeks were very limited. The following statement may seem surprising, but it can explain a great deal about the nature of Greek cosmology and cosmogony: the Greeks had no conception of gravity. Of course, they knew that if you released a heavy object it fell to the ground. They had no idea, though, of bodies having a mutual gravitational attraction, or of an object falling because of the gravitational attraction of the earth. Instead, they had to explain such phenomena in other ways. So early cosmologies had a direction to the cosmos, a top and a bottom, with heavy objects falling from one to the other. Hence the problem of why the earth appeared not to be falling. The Greeks began to realise the problems, though, and moved to a further stage of sophistication. Aristotle tells us that:

  There are some, such as Anaximander among the ancients, who say that the earth rests on account of its likeness. It is fitting that what is established in the centre and has equal relations to the extremes should not move up, down or to the side. It is not possible for it to move in opposite directions at the same time, and so necessarily it remains still.

  So the earth was central and immobile, and would remain so without any means of support. Furthermore, the earth was believed to be spherical. From this time on, it was the view of every educated person in ancient Greece that the earth was a sphere, and not flat. They supported this view with observations. They saw the shape of the earth’s shadow cast on the moon during an eclipse, and were aware that if you journeyed much further south than Greece, different stars could be seen in the night sky. At sea, the appearance of ships over the horizon was explained by a spherical earth. The Greeks explained the fact that we stick to this spherical earth by means of a ‘like-to-like’ principle. They held that like things attract, and since we are made of the same sort of stuff as the earth (a radical thought in itself), we stick to it.