[In the following excerpt, Hussey examines Anaximander's philosophy in the larger context of Milesian cosmology.]

The Theogony of Hesiod is very likely the earliest work of Greek literature that we possess. Its author lived in Boeotia, on the Greek mainland, and can be plausibly dated to near the beginning of the seventh century. The Theogony is an attempt to construct a unified genealogy of the gods. It is far from being merely a reworking of traditional Greek stories. The chief deities of the Greeks have a prominent place; but the story which looms largest—the 'Succession Myth', in which Uranus is deposed by his son Cronus who is in turn succeeded by his son Zeus—is of Near Eastern origin, though it had perhaps arrived in Greece in the Mycenean age. What is more, the well-known gods are surrounded by a host of others not often, or not all, worshipped by Greeks, and in many cases 'invented' by Hesiod himself. These others correspond to features of the universe which Hesiod thought important: we find such diverse divinities as Earth, Night, Rivers, Sleep, Strife, Victory, and so on. Hesiod is not personifying or allegorising; he believes in the existence of all his gods alike. What is important is that he is led to assert their existence, and to assign them a particular place in his genealogy, only partly on the strength of mere tradition. Usually, the deficiencies of tradition are supplied or corrected by Hesiod from considerations of what is reasonable. Sleep, for instance, is clearly an important god; it is reasonable that he should appear in the genealogy, and clearly reasonable that he should figure as the son of Night.

What Hesiod does in the Theogony is like Presocratic thought in many ways. He attempts to create a complete, unified and reasonable picture of the workings and history of the universe. He employs a single basic mechanism (the begetting of gods by gods) to achieve this picture. He is by no means constrained by tradition, and he is open to non-Greek ideas. Yet between Hesiod and even the earliest Presocratics there is a great gulf, created by a revolution in thought.

In order to see more clearly what this revolution was, it will be helpful to move on nearly two hundred years to look at the theological opinions of Xenophanes of Colophon, an Ionian born about the mid-sixth century. Xenophanes is probably not an original thinker, but he is important because the surviving fragments of his works contain the first certain statements of a theology which in sixth-century Greece was new and revolutionary:

One god there is, greatest among gods and men, in no way like mortal creatures either in bodily form or in the thought of his mind (fr. 23).

The whole of him sees, the whole of him thinks, the whole of him hears (fr. 24).

He stays always motionless in the same place; it is not fitting that he should move about now this way, now that (fr. 26).

But, effortlessly, he wields all things by the thought of his mind (fr. 25).

Corresponding to these positive statements, there is sharp criticism of traditional views, including those of Hesiod:

But mortal men imagine that gods are begotten, and that they have human dress and speech and shape (fr. 14).

If oxen or horses or lions had hands to draw with and to make works of art as men do, then horses would draw the forms of gods like horses, oxen like oxen, and they would make their gods' bodies similar to the bodily shape that they themselves each had (fr. 15).

The Ethiopians say their gods are snub-nosed and black-skinned, the Thracians that they are blue-eyed and red-headed (fr. 16).

Homer and Hesiod have attributed to the gods everything which brings shame and reproach among men: theft, adultery and fraud (fr. 11).

For the source of this radical monotheism, so foreign to the traditional Greek religion, it is reasonable to look first to the Near East. There seem to have been monotheistic tendencies both in Iranian and in Hebrew religious thought at this time as well as in Greece itself. Yet whether or not any inspiration came from these quarters, Xenophanes' theology is still something quite new. In attacking head-on the traditional beliefs and putting forward utterly different ones, Xenophanes makes no appeal to the authority of a prophet or teacher, still less to any personal revelation. He relies entirely on certain general principles—certain conceptions of what it is reasonable or fitting that a god should be. Further indications of this way of argument are preserved in other reports about Xenophanes: he argued, for instance, that it cannot be that one god is ruler of other gods (as in traditional religion), since it was 'contrary to divine law' that gods should have masters.

This way of thinking, it must be repeated, was something quite new. For the first time, a conscious and deliberate attempt had been made to set up a standard of what was and was not 'reasonable' or 'fitting' in theology. Everything was to be judged in terms of this standard alone, and the authority of tradition, or of a general consensus, or of a great teacher, was to count for nothing. By the application of this method, a doctrine of great generality and coherence was produced.

Xenophanes … has been introduced here … because it is by working back from his fragments that one may best hope to understand the intellectual atmosphere of the earliest Presocratics, the thinkers of sixth-century Miletus….

Miletus, commercially the leading city [of early Ionia] shared in these developments as well as being particularly accessible to Near Eastern influence. What seems especially important for the revolution in thought is the emergence of the concept of law as something determinate, impartial, and unchanging, and the spread of political equality. A debate between equals, in the popular assembly or the law-courts, must be conducted by appeals to general, impartial principles of law or reason—otherwise the parties will not be equal. The notion of 'reasoned argument' will begin to develop. There will grow up a habit of seeing particular situations as applications of a superior, abstract law. And law of this kind will be seen as the necessary arbiter of any complex whole in which order is apparent.

In this way, the new kind of thinking apparent in Xenophanes can be plausibly linked with the equally new political and social developments of seventh- and sixth-century Greece. One would expect the Milesian thinkers to fit into the same sort of context. As far as can be seen from the evidence, which is sparse and difficult to interpret, they fit extremely well. What follows is a reconstruction of Milesian thought which tries to take account of the evidence but which necessarily goes beyond it in places, and which is guided by the ideas which have been outlined.

Over some period in the first seventy years of the sixth century was spread the active life of three citizens of Miletus: Thales, Anaximander and Anaximenes, of whom Anaximenes was at least slightly younger than the first two. Hardly anything is known about the lives of these men. They must have been known to one another, and it is reliably reported that Thales and Anaximander were close associates. These three produced the systems of ideas about the nature of the universe which, at least since Aristotle, have been recognised as a new beginning. Anaximander and Anaximenes set out their systems in writing—two of the earliest Greek prose treatises—but Thales wrote nothing. In consequence, very little reliable information indeed is to be had about his ideas: our best informant, Aristotle, makes it clear that what evidence he could find was meagre and at second hand; at best, it came from the other Milesians. Before the three are considered separately, the main lines of the 'Milesian' view of the universe will be given. If an opinion or idea is described, in what follows, as 'Milesian', this will mean that it appears in Anaximander or Anaximenes and was, for all we can tell, common to all three thinkers.

For the theological beliefs of the Milesians, the only reliable direct evidence is in a passage of Aristotle's Physics (203^b 3-15). This suggests that the early natural philosophers, and Anaximander in particular, held that there was a single boundless all-powerful and immortal divinity which encompassed and controlled the universe. A theology of this kind would be close to that of Xenophanes, and it is reasonable to suppose that the arguments by which it was supported were similar.

It is clear that this kind of theology, supported by this kind of argument, will have far-reaching consequences for cosmology. The method of Hesiod's Theogony, in particular, will no longer be an acceptable way of producing a coherent account of the structure and workings of the universe. Since these are now dependent on the power of the unique supreme god, it is necessary to discover, if possible, the ways in which that power is exercised; to discover, therefore, the plan upon which God controls the universe. There were those who thought the enterprise hopeless: the mind of God was inscrutable and of infinite complexity, so that the order of the universe was inexplicable by man. This was the belief, for example, of the author of the book of Job, in the fifth century, and, in Greece of the same period, of the poet Pindar, whose poetry is permeated by a feeling for the sheer irreducible complexity of phenomena both physical and mental. The Milesians were of another mind: they supposed, equally with some support from observed facts, that the universe, being controlled by a supreme divinity worthy of the name, must necessarily be a universe of order, of lawlike regularity, and of intellectually satisfying construction. To hold this belief inevitably inclines men to be naively optimistic and to underrate the subtlety of nature. Their constructions are doomed always to turn out crude by comparison with reality. As Pindar said, 'They pluck the fruit of wisdom when it is unripe' … and with these words he dismissed the first century of Presocratic thought. The sneer, coming from Pindar, is no cheap one; but it applies if at all to the whole history of all sciences, not only to the first Presocratics.

The problems that most concerned the Milesians can be reduced to the question: what are the relations between the supreme power in the universe, 'the Divine', and the observable world-order? The Milesians aimed to find an answer which would square both with the observed facts and with what they held to be necessarily true about the supreme god.

The observable world-order is, for them, a bounded system of earth, sea, murky lower atmosphere, translucent sky, and the heavenly bodies, together, probably, with a hard outer shell to which the fixed stars may have been thought to be attached. This system behaves, in broad outline, with regularity, the principal changes repeating themselves in daily and yearly cycles. These easily observable cycles must have been the best guarantee for the Milesians of the existence of a controlling law in the universe: the parallel with the periodic rotation of political office necessary among equals was close at hand. Beyond this system, and unlike it not bounded in space or in time, is 'the Unbounded' (to apeiron) which is the supreme divinity and controls the whole universe. Being alive, it is perpetually in motion.

This concept of 'the Unbounded' is so important that something more must be said about its history and significance. The word apeiron is a negative adjective in the neuter formed from the noun peirar or peras. This noun has various applications in early Greek, most of which can be summed up by saying that the peras of X is that which completes X in some respect or marks the completion of X. So 'to apeiron' is 'that which cannot be completed', without any necessary specialisation to a spatial or a temporal sense. But the spatial and temporal senses were the most natural for it to bear at this time, namely, 'spatially unbounded' and 'unending in time'.

The most obvious role of 'the Unbounded' in the Milesian scheme was that of sustaining the observed world-order. What is beyond the edge of the observ able region, and why does everything not fall down? The Unbounded is 'outside' and keeps the world-order in its place. What keeps the orderly cycle of change going, and moves the heavenly bodies in their courses? The Unbounded, which never gives out, supplies the necessary motive power. In giving such answers to such questions, the Milesians were looking at the observed world-order 'from outside', and contrasting its finitude in space and time with the boundlessness of God. This contrast is encapsulated in another important word, kosmos (plural: kosmoi). As a technical term, meaning a 'world-system' containing the components of the visible world-order, this was current in the fifth century, and there is no reason why it should not have been coined in this sense by the Milesians, who would certainly have felt the need for a term of this meaning.

To look at our kosmos from the outside is to become aware that it may be not the only kosmos in the universe. The Milesians almost certainly held that there existed at any time an unlimited number of kosmoi, dotted about in the Unbounded, and their reasoning has probably been preserved by Aristotle (Physics 203^b 25-8), though he does not attribute it: if there is a kosmos here, in the Unbounded, then why not elsewhere, since there are no privileged places in the Unbounded? It is an appeal to the equality under cosmic law of all places in the universe, or (as we should say) to the principle of Sufficient Reason, of which Anaximander made striking use in another connection (see below).

A kosmos, by contrast with the Unbounded, was essentially not divine, though it was produced by creation by and from the Unbounded; it was finite, both in space and in time, having both an origin and an end. Here the obvious problem is to explain how a kosmos is created and how it is kept going, agreeably with the observed facts and with theology. All the Milesians were concerned with this problem, and gave different answers which can be partly reconstructed with greater or less probability. It becomes necessary to take them one by one.

Thales, the first Milesian thinker, was obviously a remarkable figure in public life, who by the fifth century had become legendary as a man of practical ingenuity. About his ideas, as has been explained, hardly anything can be counted certain. All that is possible is more or less plausible speculation, which must begin from the reports of Aristotle (esp. Metaphysics 983^b 20-7) that Thales was the 'pioneer' of natural philosophy, that he was said to have held that water was the origin of all things, and that the earth was supported by water. The emergence of the whole universe from an original mass of water, and a cosmic scheme in which there are waters both below the earth and above the firmament, are ideas which appear throughout the ancient Near East, and no doubt Thales drew from that source. But it is still necessary to explain why he took up these particular Near Eastern ideas, and what he used them for. Here a suggestion of Aristotle seems relevant. What water is needed for is life, and the dependence of life upon water is starkly obvious to every inhabitant of the Mediterranean region. This would indicate that Thales was primarily concerned to account for the life in the universe, and in particular the motive power that created the kosmos and kept it going. Another scrap of evidence says that Thales equated being alive with the possession of motive power, and, applying this principle, concluded that lodestones were living things (Aristotle, de Anima 405^a 19-21). Water, then, may have been identified as the fuel or the mover of the universe; things in the kosmos that could cause change had originated from water and retained its properties, some more than others. That even hot and dry things might be 'nourished' by water was suggested by the idea that the sun draws up water from the sea to feed itself—this idea was certainly current in the fifth century. And that moisture could create even dry and solid things was suggested not only by the facts of animal reproduction, but by the apparent turning of the sea to dry land at Miletus itself—a phenomenon due to the deposition of silt by the river Maeander.

This is at best conjecture, and any suggestions about the theological ideas of Thales must be equally conjectural. Aristotle (de Anima 411^a 8) attributes to him the saying 'all things are full of gods', which suggests that he was prepared to regard all forces in nature as equally divine—a view which would clearly fit in with the derivation of all forces from a divine wateriness.

Such speculations about Thales are not entirely in the air. They derive some degree of confirmation from what can be known of Anaximander, the friend of Thales. About Anaximander's opinions there is at least evidence which can be presumed reliable, within limits, derived from two witnesses, Aristotle and Theophrastus, who had read the book in which Anaximander had set down these opinions. This evidence is still very difficult to handle: it is often hard to separate what Aristotle and Theophrastus found in Anaximander's book from the interpretation they put upon it. For such reasons, there is wide divergence of opinion about fundamental questions in Anaximander. The following account is put, for convenience of exposition, rather dogmatically; much is controversial, as may be seen from any of the books referred to in the notes.

The foundation of Anaximander's system, as has been said, was the contrast between the Unbounded and the world-systems (kosmoi). Now for Anaximander the most important forces at work in the kosmoi were what were later called 'the opposites': pairs of opposed entities of which the most frequently invoked were 'the hot' and 'the cold', 'the wet' and 'the dry'. These were conceived of neither precisely as substances nor precisely as qualities, these distinctions being post-Socratic. The 'opposites' were above all forces, agents of physical change, each present in varying degrees at different places. There is no reason to think that Anaximander went beyond ordinary observation in what he said about the relations of these 'opposites' to such obvious constituents of the world as earth or water or fire. There is, further, every reason to suppose that he did not make clear in any precise way the relation of the 'opposites' to the Unbounded out of which they came. For if he had done so, Aristotle and Theophrastus would not have been as puzzled as they were about how to fit him in to their own scheme of classification. The Aristotelian scheme of classification of previous 'physical speculators' (phusiologoi) demanded that something like the Aristotelian concept of 'material cause' should have been in the minds of those classified. It was then possible to ask whether a particular thinker had taken the universe to contain one or more material causes. Anaximander might be pressed in either direction. Aristotle himself takes, in two places (Physics 187^a 20-1; Metaphysics 1069^b 18-24), the view that Anaximander's Unbounded (taken to be the material cause of what was in the universe) was meant to be a mixture of all the 'opposites', which Aristotle seems to have thought of as playing the role of material causes in Anaximander's system. Yet Aristotle noticeably does not venture to include this interpretation of Anaximander in the first book of the Metaphysics, which contains his most considered remarks on the early thinkers. And Theophrastus ([H. Diels and W. Kranz, Die Fragmente der Vorsokratiker, 6th ed., Berlin, 1951; hereafter DK] 12 A 9^a) recognised (as it seems) that there was not sufficient evidence to decide between this interpretation and another one, according to which all the 'opposites' were simply modifications of the Unbounded, and there was only one material cause, namely the Unbounded itself, whatever that might be.

The difficulty in which Aristotle and Theophrastus found themselves in trying to classify Anaximander is instructive in several ways. It is an excellent example of the classic pitfall in the history of philosophy, conceptual anachronism. It shows the limitations of Aristotle as a historian of thought. Again, the vagueness of Anaximander on the point at issue shows that not merely the Aristotelian concept of 'material cause' but even a more informal concept of 'matter' or 'material substance' was as yet not in use, and thereby sets in relief the achievements of Anaximenes, Heraclitus and their successors in working forwards to such a concept. Those to whom it seems paradoxical that the notion of a thing's 'matter' or 'substance' should be less immediate than that of its origin or past history should look at the questions that God puts to Job out of the whirlwind (Job chs. 38 and 39). These are good examples of the kinds of question that would be put to the Presocratics. Many are about the origins and motive powers of things, none about their 'matter' or 'substance'.

It does not follow that Anaximander said nothing about the relation of the 'opposites' to the Unbounded, only that he is likely to have concentrated on saying how the opposites came out of the Unbounded to create a world-system. For this part of Anaximander's account there is some evidence, though as usual it is difficult to interpret and coordinate it. We are told that the cause of the separation-out of the 'opposites' was the perpetual movement of the Unbounded. This is very vague, and the report (in DK 12 A 9) is of doubtful standing. Firmer ground is provided by indications in Aristotle (esp. de Caelo 295^a 9-14) that a 'whirl' (dinē), a vortex movement, was important in the creation of a kosmos. It looks as if the dinē was used to explain both the separation of the kosmos into heavy and light components and the circlings of the heavenly bodies. When water containing particles of varying kinds has been stirred in a bowl, the heavier particles tend to sink and to congregate about the axis of rotation, while the lighter ones execute their revolutions higher up and further from the axis. On this model it was posible to account for the formation of the earth 'below' and the movements of heavenly bodies 'above'. Whether the 'whirl' had the more general function of separating out the 'opposites' is uncertain. It seems unlikely in view of the other evidence. A doxographical fragment derived from Theophrastus gives this account of the first stage of cosmogony:

He [Anaximander] says that, at the origin of this world-system, that which, coming from the Eternal, was generative of hot and cold was separated off, and that this produced a kind of ball of flame which formed around the mist in the region of the earth, like the bark around a tree (A1O).

If the simile of the tree and its bark goes back to Anaximander, as seems probable, he was being guided here by an analogy with the formation of living things. The word 'generative' (gonimon) points in the same direction. In addition to these clues, there is the general reflection that for the creation of a kosmos from the Unbounded it is difficult to think of any natural analogy except from animal reproduction, and that Thales may have used analogies of this kind. All this suggests that the origin and development of a kosmos may have been thought of as like that of an egg or an embryo. The idea that this kosmos began as a 'worldegg' certainly appears in 'Orphic' poems which are probably later than Anaximander and in the comic cosmogony in Aristophanes' Birds, not to mention certain Hindu scriptures in which an original deity impregnates itself. More generally, an analogy between the kosmos and an animal was taken seriously by several thinkers of the Presocratic period, as will be seen.

It must not be thought that there was any essential conflict for Anaximander between the 'mechanical' model of the dinē and the 'biological' model of the egg or embryo. Anaximander was not committed to explaining exclusively by analogies of one sort or another, and did not (in all probability) press any of his analogies very hard. Even in the last Presocratics the process of cosmogony is explained only in rather vague, intuitive terms. Yet the inherent disparity between biological and mechanical explanation was to become a source of confusion.

In the developed kosmos, the working of each of the 'opposites' is thought of as a continual struggle against its opposed twin. Each gains ground at certain times in certain places, and loses ground correspondingly at other times and places. It is natural to ask whether these gains and losses involved the transformation of one 'opposite' into another, the destruction of one by another, or merely the advance of one 'opposite' and the retreat of the other. Theophrastus seems to have asked this question, and to have answered it by claiming that Anaximander's 'opposites' turned into one another. Unfortunately, the passage derived from his report on which this conclusion is based does not suggest that Theophrastus had any very strong grounds for his claim. The passage runs as follows:

[Anaximander says that] the destruction of things that are takes place by their turning back into those things from which they had their origin, according to necessity; for they make requital and recompense to one another for their injustice, according to the assessment of Time. (Such are the rather poetical phrases he uses in speaking of them) (A9 and Bl).

This passage cannot well refer to anything except the struggle of the 'opposites', and if so it is evidence that Theophrastus saw this struggle as a succession of transformations, but does not explain why. It may very well be that Theophrastus' reasons have been lost in abridgement.

Nevertheless, this passage is still very interesting. The comment at the end shows that at least some of the less prosaic expressions used were quoted by Theophrastus from Anaximander's book. It follows that the phrases rendered by the words italicised above are probably Anaximander's own phrases. They bring us back to the problem of how the Undoubted controls the events in each kosmos, and thus to the idea of the kosmos as governed by law. It is clear that 'injustice' consists in the encroachment by one 'opposite' on the other, and that the 'requital' is the restitution of the unjust gains and a corresponding loss as well. There is an overall regulation of the fight; however it may go in small areas of space and time, it is evened up in the long run over the whole kosmos, the cycles of day and night, and of the seasons, being the most obvious evidence for the existence of such a law. This law is not guaranteed by some inherent equipollence of forces, but imposed externally, by the intervention of the Unbounded. This at least is the most reasonable conclusion from various indications. We know in general that the Unbounded 'governs' the universe, and so is the natural source of physical law. Moreover, the lawlike behaviour occurs 'by necessity' (kata to chreōn), which implies a power imposing the necessity, and 'according to the assessment of Time' (kata tēn tou chronou taxiri). The significance of this last phrase is, unfortunately, disputable, but it is quite possible that 'Time' is here thought of as the name of a divine power, namely the Unbounded. For the idea of Time as a divine power occurs, not only in Iranian religion, but in other Greek sixth-century writers: Solon, Pherecydes and Heraclitus.

Each kosmos lasted only a finite time, but on the later stages of its existence there is no direct information. Presumably it aged like an animal or ran down like a clock, the rotatory movement which was its life and gave it its form slowing down and eventually stopping, whereupon its contents would be reabsorbed into the Unbounded.

Within this grandiose framework, Anaximander filled in a great number of smaller details about our kosmos as it now is. Here is a list of some of the questions to which he offered answers (it is again worth while to compare Job chs. 38 and 39): how the heavenly bodies were formed; at what distances they are from the earth; what is the cause of eclipses; why the earth remains in the same place; what is the shape of the earth; what are the causes of winds, rain, thunder, lightning, earthquakes and the annual flooding of the Nile; what was the origin of animals and mankind. He also constructed a map of the earth's surface. Space does not allow treatment of all these details, but two points of particular significance must be mentioned here.

One is the explanation of why the earth remains in the same place. This problem, as Aristotle remarks, exercised all the Presocratics, just as it did many other people. With the single exception of Anaximander, all the early Presocratics (and most later ones) supposed that the earth had some material support: a pillar of solid earth (Xenophanes) or a cushion of air (Anaximenes) or water (Thales), on which it floated. Anaximander appealed instead to symmetry. There was no reason why the earth should move downwards rather than in any other direction, since it was symmetrically placed in the middle of the kosmos. This explanation might seem to imply that Anaximander took both earth and kosmos to be spherical; in fact we know that his earth was cylindrical, as befitted the product of a cosmic vortex. The appeal to symmetry may therefore have proceeded in two stages rather than in one, using first a symmetry about a horizontal plane through the earth, and secondly a radial symmetry around the axis of the cosmic rotation. If this is right, he ought in consistency to have maintained that the flat surface of the earth which, relatively to us, was the under surface, exhibited the same features as the 'upper' surface—rivers, mountains, animals and so on; and that there was correspondingly another set of heavenly bodies 'below'. A faint trace of this doctrine appears in the doxography.

In any case, this explanation is the earliest certain instance of an appeal to the principle of Sufficient Reason—a principle which, as has been suggested, is characteristic of the spirit of Milesian cosmology.

The second important point of detail is Anaximander's account of the origin of animal and human life on the earth. Animals, including human beings, he supposed to have been originally produced by spontaneous generation from mud, by the action of the sun's heat on moist earth. Of the beginnings of the human race he held a remarkable theory, which was clearly designed to take account of the fact that the new-born human infant is unable to fend for itself. The prototypes of human beings were originally produced as fish-like creatures, encased in a spiny bark, and inhabiting the water; in due course, on reaching maturity, they took to the dry land and shed their fish-like exterior, emerging in human form. This striking 'anticipation' of modern theories of human phylogeny suggest that Anaximander may have known something of the development of the human embryo. If so, this would add some plausibility to the attempt to find biological analogies in his cosmogony.

Anaximander's system was, naturally, open to objections on points of detail, since it offered solutions to all the problems of cosmology which most interested his contemporaries. It is more important that it was in danger of internal incoherence. Not only did Anaximander give no clear explanation of how the 'opposites' existed in the Unbounded, or of how they alternately prevailed in the kosmoi. He left it unexplained how, if everything was regulated by divine law, there could occur even local and temporary 'injustice'. All these difficulties may be comprehended in the general problem: how far is the deity identical with the worlds it creates and governs, how far are they distinct from it?

As soon as Anaximander's ideas were discussed in the spirit in which they were propounded, this question must have begun to emerge. It is therefore not surprising that the main innovation of the third Milesian thinker, Anaximenes, is an attempt at a new kind of answer to the problem. Remaining within the 'Milesian' framework outlined above, Anaximenes declared that the contents of the world-systems that emerge from the Unbounded deity are produced from it, and are interconvertible with it and each other, by processes of condensation and rarefaction. In other words, some notion approximating to that of Aristotle's 'material cause' is invoked or constructed.

This point deserves further precision. If we are to be able to say that Y is the 'same thing' as X, what seems to be required is not merely that X should change into Y in a fairly continuous fashion, but also that this change should be intelligible and lawlike, in other words that it should appear explicable in familiar terms, and should proceed according to definite laws which place restrictions on the ways in which X may change and what it may change into. Further, the change should ideally be reversible, so that X can be recreated from Y; and at any rate we must be able to reidentify in Y those properties of X which we take to be most essential and characteristic of X. All these features can be found in Anaximenes' theory. It is not suggested that he identified each of them, still less that he made a self-conscious conceptual analysis. Rather, the the whole nexus of conditions will have emerged as 'natural' in the circumstances, given the need to produce, within the Milesian framework, a lawlike process of change linking the deity to the kosmoi.

If this account is on the right lines, then an essential step in Anaximenes' construction was an appeal to certain facts of experience. Anaximenes seems to have been guided by the observation that the more closely anything is compressed, the harder and more solid it becomes. This suggests that we may explain solid, liquid and gaseous things by the varying degrees of compression of one basic material. It is natural to take as a leading fact here the interconvertibility of water and snow or ice; Anaximenes did so, and stated more generally the principle that heat was associated with expansion or rarefaction, cold with compression or condensation. Going on from this, he constructed a spec trum in which all the main components of our kosmos were ranged according to their degree of condensation. The spectrum was: fire, air, wind, cloud, water, earth, rock.

This theory gave each kosmos an internal coherence far beyond what it had had for Anaximander. But the internal coherence only reflected the external coherence between the kosmoi and the unbounded deity. For Anaximenes gave the deity too a place on the spectrum, by declaring that it existed in the form of air. The consideration that determined this choice was almost certainly the fact that animals must breathe in order to live. This fact had long been connected with the popular conception of the psuchē or life-principle as the 'breath of life' which left the body at death. There is in the doxography a report (DK 13 B 2) that Anaximenes made an explicit analogy between the role of psuchē in the living body and that of the divine air in the kosmos. The report shows clear signs of having been influenced by Stoic ideas, but this does not mean that its kernel is not authentic; the Stoics embroidered the doxography rather than invented it. If this is right, the divine air of Anaximenes is another sign that, for the Milesians, the most characteristic property of the controlling deity was that he was alive and could initiate movement.

This new general theory of physical change was Anaximenes' sole important contribution. It seems unlikely, to judge by the doxography, that he worked it out in much greater detail or made applications of it to particular problems. Some details of his cosmological speculations are preserved, but they bear no obvious relation to the general theory.

This chapter has been focused, up to this point, upon the ideas and attitudes of the Milesian thinkers, with some suggestion of how they are to be related to the political and economic developments sketched in the first chapter. But it is interesting, and may be important, to consider the relations of Milesian thought to the whole intellectual history of the ancient Near East. The very brief survey of Ionian horizons in the first chapter showed, at least, the great variety of possibilities for fruitful transmission of ideas from the barbarians, and especially from the old urban civilisations of the 'Fertile Crescent'. The evidence in detail for such transmission has been growing gradually stronger in the last hundred years as the written records of those civilisations have been unearthed and interpreted. Fresh documents may yet be found which will warrant new conclusions.

If we assume, however, that the evidence so far available is not seriously misleading, and if the view of the Milesians taken in this chapter is correct in general, then it can be said that they were indisputably influenced from the Near East, but that such influence was of an incidental, secondary kind, in a sense to be explained. The core of the Milesian revolution, namely, the development of a reformed theology based on general principles, and the correlative vision of a universe governed by universal law, cannot be paralleled, as yet, from anywhere outside Ionia. The earlier Hebrew prophets, and the Iranian prophet Zoroaster, may have had a vision of the nature of God as austere as that of Xenophanes, but their expression of it is enmeshed in the particular circumstances of themselves and their society. And because they lack such a vision, the cosmogonies of Babylonia, Canaan, or Egypt contain intelligent speculations and inferences, as well as the general notion of an established world-order, but are unable to free themselves definitely from the entrenched belief in the arbitrary power of an uncoordinated multiplicity of gods, and their world-systems evolve in a sequence of events without any internal necessity.

When this is granted, it may be readily admitted that on many great and small points of cosmogony and cosmology, the fact of borrowing is as certain as such things can be. One would expect the Milesians to have turned to the Near East as a source of ideas and of knowledge, and they did. But because they were borrowing for purposes of their own, they borrowed selectively and never wholesale. So Thaïes was stimulated by a cosmogony widespread in the Near East to see water as the origin of all and the support of the earth. Anaximander's Unbounded has been traced both to Iranian and to Babylonian sources, and there may well be something in both conjectures. Certainly there are several other points which point to Babylonian or Iranian influence on Anaximander, and equally certainly the religious ideas of the Iranian peoples will have had much to appeal to a Milesian thinker. Less certain is the attempt to connect details of Milesian cosmogony with those of the cosmogony attributed to 'Sanchuniathon' and other Phoenician speculations. 'Sanchuniathon"s ideas are preserved only in a later Greek translation, but they are alleged by the Greek source to be of Phoenician origin and of great antiquity. This claim has come to seem more and more reasonable as knowledge of the ancient Near East has increased. 'Sanchuniathon' seems closer in spirit to the Milesians than any other Near Eastern cosmology—perhaps it is significant that he is Phoenician. However this may be, in spite of the many points of possible contact, there is no convincing proof that the cardinal ideas of Anaximander's system were anticipated inside or outside Greece, and still more is this true of Anaximenes.

A special question is that of borrowings of mathematical and astronomical knowledge from Babylonia and Egypt at this time, by the Milesians or by other Greeks. The nature of the Babylonian and Egyptian knowledge has been briefly indicated in the first chapter. It would be in keeping with the general character of the Milesians that they should take over and assimilate this knowledge if it was available to them. Unfortunately the evidence for the astronomical speculations of the Milesians, or of any sixty-century Greeks, is sparse and difficult to handle. The subject remains highly controversial, but it seems rather likely that some very rudimentary astronomical (and mathematical) knowledge was transmitted to Ionia at this time.

In connection with the question of Near Eastern influence, it is right to mention what is known of other cosmogonies produced by Greeks in the late seventh and early sixth centuries. The poet Alcman, writing in Sparta not much if at all later than 600, incorporated in one of his choric songs a set of cosmogonical ideas in which there are things suggestive both of the Milesians and of the Near East. And in the sixth century Pherecydes of Syros composed a prose theogony which related in turn: the origin of the gods from three original gods who 'always existed'; the constructing of the rest of the world as it now is by one of those three, the creator-god Zas; and the final establishment of order by Zas after he had overcome a snaky monster representing the forces of confusion. These two examples show that, as is not surprising, interest in cosmogony was strong throughout the Greek world at this time, and they are good evidence of an openness to Near Eastern ideas. But it would be very misleading to class Pherecydes, and still more Alcman, with the Milesians as 'Presocratics'. For if the label 'Presocratic philosopher' has any point, it is that it marks off the Milesians and their successors as something new in the history of thought. Pherecydes and Alcman are, in this classification, on the same side as Hesiod and the ancient Near East. To put it more sharply, in the history of the human mind the Milesians are of cardinal importance, and Alcman and Pherecydes not at all. It has been the object of this chapter to explain where the difference lies.