Discuss the origin and development of Greek cosmology and cosmogony from the 8th Century to the 5th Century BC.

     With the philosophy of Anaximander proposing that our universe is comprised of a number of different elements, his student returned to the conviction that there must be a single kind of substance at the heart of everything, and he proposed vapour or mist as the most likely candidate (Cf. Arist. Metaph. i. 3 ; 984 a 5). Not only does this warm, wet air combine two of the four elements together, but it also provides a familiar pair of processes for changes in it’s state: condensation and evaporation. Thus, in its most basic form of breath or spirit, Anaximenes's air constitutes the highest representation of life (Cf. Cic. de Nat, Deor. i. 10 ; Dox. 531). Anaximenes's notion of successive change of matter by rarefaction and condensation had a lasting effect on Greek thought. 

     Despite how intriguing the Milesian speculations are, they demonstrate only the most primitive form of philosophical inquiry. Although they opposed each other on a number of points, each of the thinkers appears to have been satisfied with proposing his own views in relative isolation from those of his teacher or contemporaries. Later generations initiated the move toward critical thinking by directly arguing with one another, a step that would inevitably lead to a development in the practise of philosophical debate.

     During the same period as the Milesian thinkers, the Greek colony in Italy at the same time devoted much more concern to practical matters. Followers of the legendary  developed a comprehensive view of a human life in harmony with the entire natural world (Cf. Arist. De caelo ii. 13; 293 a 19). Since the Pythagoreans persisted for many generations as a semi-religious sect, concealing themselves behind a veil of secrecy, it is difficult to recover a detailed account of the original doctrines of their leader, but the basic premises are clear. 

     Pythagoras was interested in mathematics: he discovered a proof of the theorem that still bears his name, engaged in extensive observation of the apparent motion of celestial objects, and described the relationship between the length of strings and the musical pitches they produce when plucked. In each of these aspects of the world, Pythagoras saw an order of regularity, occurrences that could be described in terms of mathematical ratios.

     The aim of human life, then, must be to live in harmony with this natural regularity. Our lives are merely small portions of a greater whole (Cf. Aet. Plac. i. 3; 280). Since the spirit (or ‘breath’) of human beings is ‘divine air’, Pythagoras speculated, it is naturally immortal; its existence naturally outlives the relatively temporary functions of the human body (Cf. Gorg. 493 A.). Pythagoreans therefore believed that  "transmigrates" into other living bodies at death, with animals and plants participating along with human beings in a grand cycle of reincarnation (Cf. Aet. Plac. v.1; 415), a notion that would last in the philosophical tradition of the west.

     We are beginning to see that despite the additions of scientific and mathematical research into contemporary cosmology, the philosophical ideas are still incredibly similar to those of the 6th century. However, during the , another significant development in the history of rational thought was beginning to emerge. The Greek philosophers began to engage in extended controversies that represented a movement toward the development of genuinely critical thinking. Although they often lacked enough common ground upon which to adjudicate their disputes and rarely engaged in the self-criticism (a characteristic of genuine philosophy), these thinkers did try to defend their own positions and attack those of their rivals by providing attempts at rational argumentation. With this in mind we now move on to look at the ‘critical cosmology’ of later Greek speculation.

     Dissatisfied with earlier efforts to comprehend the world,  earned his reputation as "the Obscure" by delivering his teachings in deliberately  form. The structure of puzzling statements, he believed, mirrors the chaotic structure of thought, which in turn is parallel to the complex, dynamic character of the world itself. In this intrinsic method of explaining ideas we see a move towards dialectical philosophy, an area which would have a lasting effect on Western thought.

     Rejecting the Pythagorean ‘’ (Cf. Above section on Pythagoras) as peaceful coexistence, Heraclitus saw the natural world as an environment of perpetual struggle and strife. "All is flux," he supposed; everything is in constant change (Cf. Origen c. Cels. vi, 52). As Heraclitus is often reported to have said, "Upon those who step into the same river, different waters flow" (Cf. Arius Didymus ap. Eusebium P.E. xv. 20). The tension and conflict which govern everything in our experience are moderated only by the operation of a universal principle of proportionality in all things. Through the ideas of Heraclitus we see a break away from earlier cosmological speculation through the introduction of dialectical methods, which to this day plays a key role in philosophical understanding. However we must also acknowledge that Heraclitus still maintained that there was a primary substance at the centre of things, an idea first proposed by Thales. This represents a lasting rationale in Greek thought.

     Against Heraclitus’s position, the  defended the unity and stability of the universe. Their leader,  supposed that language embodies a logical system of perfect immutability: "What is, is." Since everything is what it is and not something else, he argued in On Nature, it can never correct to say that one and the same thing both has and does not have some feature, so the supposed change from having the feature to not having it is utterly impossible (Cf. Hipp. Ref. ix, 10, 5). Of course, change does seem to occur, so we must distinguish sharply between the many mere appearances that are part of our experience and the one true reality that is discernible only by intellect.

     Other Eleatics delighted in attacking  with  of his notion that the world is perpetual changing.  in particular fashioned four paradoxes about motion, covering every possible combination of continuous or discrete intervals and the direct motion of single bodies or the relative motion of several (See Appendix I). The  that results in each of these cases, Zeno concluded, shows that motion (and, hence, change of any sort) is impossible.

     What all of this raises is the question of "the one and the many." How can there be any genuine unity in a world that appears to be multiple? To the extent that a satisfactory answer involves a distinction between  and the use of  in the effort to understand what is real. This pursuit of the Eleatics set important standards for the future development of Western thought.

     In the following generation,  introduced the plurality from the very beginning. Everything in the world, he supposed, is ultimately made up of some mixture of the four elements, considered as irreducible components (Cf. Plut. Adv. Colotem, iv F). The unique character of each item depends solely upon the special balance of the four that is present only in it. Change takes place because there are two competing forces at work in the world. Love (Gr. philia) is always drawing things together, while Strife (Gr. neikos) is constantly drawing things apart. The interplay of the two constitutes the activity we see in nature (Cf. Simpl. Phys. 158, 1). Empedocles’ conception of everlasting reoccurrence is often named his ‘cosmic cycle’. Its most significant and clearest application is undoubtedly in his cosmological theory concerning the birth and death of the universe, presenting a development in Greek thought that would influence later thinkers.

     Empedocles’ rival, , returned in some measure to the  effort to identify a common substance out of which everything is composed. Matter is, indeed, a chaotic primordial mass, infinitely divisible in principle, yet in which nothing is differentiated. But Anaxagoras held that order is brought to this mass by the power of Mind (Gr. nous), the source of all explanation by reference to cosmic intelligence (Cf. Plato Kratyl. 400 A). Although later philosophers praised Anaxagoras for this explicit introduction of mind into the description of the world, it is not clear whether he meant by his use of this word what they would suppose. With the introduction of Mind the basis for his cosmological system is complete. Like the atomists that followed him, Empedocles was a dualist; and his dualism is in a sense a dualism of Mind and matter (Cf. Theophr. Phys. 164, 26), however both the members of this dualism are peculiar. Mind, like matter, is corporeal and owes its influence over matter to its fineness and purity (Cf. Simpl. Phys. 164, 24 and 156, 13). Matter itself, so far from being pure, is originally at least an infinitely divisible mixture of every form of substance that the world is ultimately to contain (Cf. Simpl. Phys. 14, 157, 7).

     The tendency to regard the universe as pluralistic took its most radical form in the work of the ancient . Although the basic outlines of the view were apparently developed by , the more complete exposition by , including a discussion of its ethical implications was more influential. Our best source of information about the atomists is the poem On The Nature of Things (Gr. De Rerum Natura) by the later Roman philosopher .

     For the Greek atomists, all substance is material and the true elements of the natural world are the tiny, indivisible, unobservable solid bodies called ‘atoms.’ Since these particles exist, packed densely together, in an infinite empty space, their motion is not only possible but also inevitable. Everything that happens in the world, the atomists supposed, is a result of microscopic collisions among atoms (Cf. Arist. On Democritus ap. Simplicium de caelo. 295, ii). Thus, as  would later make clear,  are also inevitable consequences of material motions. Although atomism has a decidedly modern ring, notice that, since it could not be based on observation of microscopic particles in the way that modern science is, ancient atomism was merely another fashionable yet deeply important development in cosmological speculation.
    With Democritus, who was a little if at all older than Socrates, the Presocratic period legitimately comes to an end. During the second half of the fifth century BC, particularly during the Peloponnesian War and under the growing influence of the Sophists, the archaic cosmological approach was gradually substituted with a more humanistic approach to philosophical investigation, in which the study of man became the first principle. This reorientation was a natural development: in part it was determined by social factors, but in part, as will have become clear in reading this account, it was the product of tendencies in the Presocratic movement itself which moved emphasis away from the religious cosmologies first put forward by Homer and Hesiod and towards a logical understanding of the universe. It is through this notion of natural development that contemporary cosmology will, in time, eventually develop further, leading humanity into new areas of speculation about aspects of our universe.

Appendix 1:

The Paradoxes of Zeno

The Dichotomy

It is impossible to move around a racetrack since we must first go halfway, and before that go half of halfway, and before that half of half of halfway, and . . . . If space is infinitely divisible, we have infinitely many partial distances to cover, and cannot get under way in any finite time.

Achilles and the Tortoise

Given a ten-meter head start, a tortoise can never be overtaken by Achilles in a race, since Achilles must catch up to where the tortoise began. But by then the tortoise has moved ahead, and Achilles must catch up to that new point, and so on. Again, the supposition that things really move leads to an infinite regress.

The Arrow

If motion occurs in discrete intervals, then at any given moment during its flight through the air, an arrow is not moving. But since its entire flight comprises only such moments, the arrow never moves.

The Stadium

If three chariots of equal length, one stationary and the others travelling in opposite directions, were to pass by each other at the same time, then each of the supposedly moving ones would take only half as long to pass the other as to pass the third, making 1=2.

Zeno's arguments are perhaps the first examples of a method of proof called  also known as ‘proof by ’. They are also credited as a source of the  method used by .

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