For example , from around the thirteenth century BCE, the Egyptians had identified the five planets visible to the naked eye (Mercury, Venus, Mars, Jupiter and Saturn) and over forty stellar constellations, including the signs of the Zodiac (Wright, Cosmology, p. 15). Greek cosmological enquiry, from the sixth century BCE onwards, wa s based on the recognition that the external universe is a well-ordered system and the conviction that this order is open to rational analysis and explanation. It wa s the strong sense that the early Greek philosophers had of the world’s orderliness that prompted the application of the word kosmos (KOO|JOS ) , which had the primary sense of ‘order’, to the physical universe. In early Greek usage, the term wa s used with reference to specific types of social orderings, such as the seating order of rowers (Homer, Od. 13.77), the order of soldiers (Homer, 77. 12.225) and wellordered political states such as Sparta (Herodotus 1.65). It wa s also used for order in a general sense (Herodotus 2.52; 9.59). 5 According to Charles Kahn, the term wa s applied to the cosmic order ‘by conscious analogy with the good order of society’ (C. H. Kahn, Anaximander and the Origins of Greek Cosmology (New York: Columbia University Press, 1960), p. 223). On e ancient tradition (Diogenes Laertius 8.48) accords Pythagoras the distinction of being the first to call the universe b y the name of kosmos, but w e cannot b e certain that he wa s responsible for this semantic move.

The earliest picture of the cosmos we encounte r in Greek literature is that assumed in the epic poems of Homer, the Iliad and the Odyssey. Th e earth is viewed as a circular, flat disc surrounded b y the great river Ocea n (77. 18.607; cf. Herodotu s 4.8), and the sky as a bowl-like hemispher e of bronz e or iron (77. 5.504; 17.425; Od. 15.329), covering the flat earth. Below its surface, the earth extends downward s as far as Tartarus (77. 8.14). Anaximander, in the sixth century BCE, pictured the earth as cylindrical in shape , like a column drum, hangin g without support in the surrounding air (G. S. Kirk, J. E. Raven and M. Schofield, The Presocratic Philosophers: A Critical History with a Selection of Texts (2nd edn; Cambridge: Cambridge University Press, 1983), texts nos. 122-4, pp. 133-4). According to the Aristotelian cosmi c model, the earth lies at the centre of the cosmos, surrounded b y a numbe r of concentric , rotating spheres, to whic h the sun, moo n and planets are attached (see further below). A heliocentric picture of the cosmos wa s proposed b y Aristarchus of Samos (b. c. 320 BCE), but this wa s almost universally rejected (Wright, Cosmology, pp. 153-6).

1. 1.1. Hesiod
2. The first gods are personifications of the main components of the cosmos, so their appearanc e constitutes the formation of the physical world. First came Chaos. After Chaos came Earth, Tartarus and Eros. Chaos then produced Erebos (dark place) and Night (night). From them came Aither (brightness) and Hemer a (day). Earth brought forth Ouranos (heaven), mountains and sea. A striking feature of this cosmogony is the primacy of Chaos. Wha t Hesiod mean t b y ‘Chaos’ wa s the subject of muc h ancient discussion and continues to b e debated. A n attractive (though not unproblematic) suggestion is that it refers to the gap between the sky and earth, which would make the first stage of creation the separation of wha t wa s formerly one mass. 1 4 Th e idea of the separation of an originally indistinct earth and sky wa s a well-established feature o f Ancient Nea r Eastern (ANE) cosmogonies. The clash betwee n the Titans an d the Olympians, and the later conflict between Zeu s and Typhoeus, takes the world to edge of total collapse. Hesiod employs colourful imagery of cosmi c catastrophe to depict the battles of the divinities (Theog. 678-705 , 847-68). With all opposition vanquished, Zeu s secures the stable existence of the cosmos. Hesiod seems to suggest that the earth is everlasting (Theog. 116-17). Philo (on who m see below) regards him as the father of the Platonic doctrine that the world is created and indestructible (Aet. Mund. 17).

1.2. The Milesians

Thes e thinkers maintained that the univers e originated from a single generative principle or arche. The y explained the emergenc e of the cosmo s in biologica l terms, as growth from a seed. Th e Milesians wer e hylozoists: they believed that the cosmo s is animate . Fo r Thales, who m Aristotle identifies as the founde r of the arche type of cosmogony, the originating principl e wa s water. Thales also seems to hav e taught that the earth floats like a piece of a wood. Aristotle, Met. 983b6. Aristotle, who is our only source of information on this point, presents Thales as teaching that all things were made of water and that water continues as the material substrate of all things. It is possible, though, that what Thales actually taught was that the earth emerged from water, and that he was simply reflecting the belief that the earth rose out of the primaeval ocean, found in ANE cosmogony and also in Homer (77. 14.201,246). But, on the other hand, Thales could well have transformed the mythological notion into a physical theory. Anaximenes, his successor, certainly believed that air was the actual material source and substrate of everything, and it is generally assumed that he was pursuing a line of reasoning instigated by Thales. See the discussion in Kirk, Raven and Schofield, Presocratic Philosophers, pp. 88-95.

1.3. Heraclitus, Parmenides, Empedocles and Anaxagoras

1.4. The Atomists

The Atomists, Leucippus and his younge r but mor e well-known contemporary Democritus, rejected the idea that the universe arose from a single material principle, such as wate r or air. In their view, the cosmos is mad e u p of indestructible particles of matte r called atoms (atomon meaning ‘uncuttable’). Thes e particles are of different sizes and shapes but are so tiny that they are below the threshold of visibility. Atoms are infinite in numbe r and mov e randomly in infinite space or void. 4 4 The y collide, bounc e bac k and interlock to form aggregates that can b e seen and touched. Th e ordered cosmo s came about whe n a mass of atoms collected in a region of the void. Their collisions caused a vortex or whirlwind and the atoms began attaching themselve s to each other to form compounds. The heavie r compound s collected at the centre thus forming the earth. Th e lighter compounds, ignited b y the whirling motion, formed the substance of the celestial bodies. 4 5 This world came into being by chanc e and necessity; there wa s n o cosmi c intelligence directing the physical processes.

1. 1.5. Plato
2. Plato dismissed the Atomists’ view that our cosmos is one of an infinite numbe r of accidentally caused worlds. H e insisted on the singularity and uniqueness of our cosmos, and maintained that the order manifested in the cosmos wa s not there b y chanc e but ha s been imposed upo n it b y a divine intelligence. Plato tells us that the cosmo s ha s been perfectly constructed (32D-33B). All existing matter ha s been used in u p its production; nothing ha s been left outside. In its formation, the elements have been perfectly combined. Th e cosmos cannot be injured b y something external to it, nor can it b e undon e b y internal disharmony. Therefore, it is not subject to decay and dissolution. Only the craftsman himself can unmak e wha t h e ha s created. But the demiurge is wholly goo d (30A) and could neve r engage in such an evil act as to destroy this consummat e achievement and wor k of art. Th e physical cosmos is thus everlasting and indestructible. It is a living creature (30CD) with bod y and soul (34B).

1. 1.6. Aristotle
2. “Aristotle maintained that the cosmos is eternal, having neither beginning nor end (De Caelo 1.10-12). The cosmos is spherical in form, and limited in extent (1.5-7). There is no empty space beyond it nor within it. He viewed matter as extending continually throughout the universe leaving no gaps. At the centre is the earth, which is encircled by concentric spheres to which the heavenly bodies are affixed. The outermost sphere, encasing the whole, is the sphere of the fixed stars. The terrestrial sphere is made up mainly of the element earth, which has on its surface water, and is enclosed by air, which is in turn enveloped by a sphere of fire. Aristotle did not, though, think that the elements were completely distinct; he allowed for their interpenetration and transformation. Above the lunar sphere, matter is of a different character. The heavenly bodies and their spheres are not composed of any of the four terrestrial elements, but a ‘fifth element’, aither (2.7). Aristotle limited change to the sublunary sphere.

For both Plato and Aristotle, perfect motion was circular. However, the planets (literally, the wanderers) did not appear to exhibit that motion consistently. They seemed to deviate occasionally from their rotations, turning back from their eastward movement in relation to the constellation and moving westward for a while – a phenomenon known as retrogradation. Eudoxus, a younger contemporary of Plato, offered a mathematical explanation of planetary movements that tried to account for this phenomenon. He proposed that the paths of the celestial bodies were produced by the rotations of concentric spheres moving at different velocities and with different axes, with the earth as the shared centre (Aristotle, Meta. 12.8.9-10). Callippus then modified Eudoxus’ theory (12.8.11). Aristotle made his own adaptations to the theory, positing the existence of no less than fifty-five rotating spheres (12.8.12-14). Aristotle thus produced an account of the ordered universe as a mechanized system. For Aristotle, the universe could not be the cause of its own movement. A prime mover was required, external to the universe: ‘something which moves without being moved’ (Met 12.7.2). Aristotle did not hesitate to call the prime mover ‘god’ (12.7.7-9), though Aristotle’s ‘god’ is not the personal deity of the Old Testament.”

1.7. Epicurus and Lucretius

Epicurus accepted the Atomists’ account of the nature of reality and the origins of the cosmos. Our world, one of an infinite numbe r of worlds in infinite space, came into existence, not b y divine agency, 5 4 but through the accidental collision and combination of atoms in an area of the void. It will eventually perish whe n the compound breaks up and the atoms disperse. He explained the life of a cosmos using a biological model. 5 5 A world grows by taking in nourishment. It absorbs atomic matte i until it reache s the peak of maturity. After growth, there is decline, when more particles are exuded than taken in, until eventually the cosmic body, no longer able to resist the external forces bearing down upo n it, become s so wea k that it collapses and disintegrates. The world is a mortal entity, the collapse of which is inevitable. Its end ma y come ‘within some short time’ . He also strikes at the belief that the cosmos ha s bee n divinely ordered and mad e for the benefit of huma n beings. He argues that the world is far too flawed to b e of divine origin (5.195-234). Most of the earth’s surface is uninhabitable, and of what is left, much is wild and infertile.

1.8. The Stoics

‘God ‘ wa s understood as the rational, active principle – the logos – present in matter (and inseparable from it), pervading it and giving it order (Diogenes Laertius 7.134). Th e Stoics wer e thus thoroughgoing pantheists (and thoroughgoing materialists), identifying the cosmos itself with god (Diogene s Laertius 7.137). The ascription of full divinity to the cosmos shows how highly they esteemed it. Plato and Aristotle rejected the notion of space outside the cosmos, but the Stoics argued for the existence of an infinite void external to the cosmos (into which the cosmos expands whe n it ignites at the conflagration). 5 9 They mad e a terminological distinction between ‘the whole ‘ and ‘the all’, which hitherto had been used synonymously: the former is the physical cosmos; the latter is the cosmos and the void together. 6 0 The cosmos is conceived in Aristotelian fashion as a series of spherical tiers, with earth at the centre and the heavenly bodies at the periphery. 6 1 Terrestrial matter divides into the four terrestrial elements: earth, fire, air and water. But these elements are transformations of a mor e basic form of matter, ‘designing fire’, to be distinguished from the element fire.62 The celestial bodies are composed of aither, which is ‘designing fire’ in its purest form, though the Stoics appear to have shied away from calling aither a fifth element. On the Stoic theory of cosmogony, the universe originates in a pur e fire (none of the Greek natural philosophers posited creation ex nihilo). Th e fiery substance change s to air and then to water, and out of the primordial wate r the four elements arise, and these combine in man y way s to mak e u p the variety of things and forms of life on earth (Plutarch, Stoic. 1053a; Diogene s Laertius 142).