Early Speculation: Cycles of Change

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Early Speculation: Cycles of Change




Turning Point . The early fifth century is a turning point in the history of Greek science, since it was then that the problem of change first began to be raised in a systematic manner. The Milesians had focused their attention mainly on identifying the basic material of the world; and the Pythagoreans turned away from that material element to look instead at the mathematical structure and form of the world. Neither group directly addressed a simple but crucial fact of everyday observation: things change.

The Cycle of Air . Change is an obvious feature of all things and is directly confirmed by the senses. But what exactly is it? And how does the fact that the world always changes impact on the ability to understand it scientifically? Anaximenes more than any other earlier thinker seems to have speculated on how one thing can turn into another. He claimed that everything is air and proposed condensation and rarefaction as the two processes that account for how air changes into everything else in the world—fire, clouds, rain, rocks, and so forth. This claim is circular. If water, for example, is nothing but condensed air, and fire is air that has been rarefied even more, then air itself is not really a unique element at all, but instead just another phase in an endless cycle. That is, it could just as easily be said that air is nothing but rarefied water or condensed fire. And if this is so, then what sense does it make to claim that air is the primordial reality?

Truth . The problem of change has two main aspects. The first has to do with what passes for an acceptable answer to the question, “What is real?” The ancient Greeks implicitly believed that whatever the true nature of reality is, that true nature must always be true. This truth is what motivated them to “save the phenomena” in the first place, by searching for something fixed and permanent beneath the constantly shifting things and events in the world. Yet, if the answer (as in the case of Anaximenes) is that this fundamental something is sometimes air and sometimes something else, have we really found what we are looking for? Does a changeable reality fit the definition of what reality really should be?

Epistemology. The second aspect of the problem of change has to do with how people can know what is real. What evidence do people have for talking about reality? What basis do people have for judging whether evidence is valid or not? How can people be sure that they know anything at all about reality? These and similar questions mark the beginning of Western epistemology, the study of the relation between the mind and the world. The Greek thinkers of the fifth century b.c.e. put these questions in a more direct form, by contrasting the mind with the senses. The mind insists that reality be permanently true, but the five senses only presents a picture of change; nothing we hear, see, taste, touch, or smell conforms to the idea of a permanent truth. Which is the true path to genuine knowledge of the world, then, reason or sensory experience?

Answers. The first response to these questions was made around 500 b.c.e. by Heraclitus of Ephesus in Asia Minor. The surviving fragments of his book are written in a deliberately obscure and riddling style, making it hard to agree on how exactly to interpret many of his claims. On the one hand, Heraclitus apparently argued that change is indeed the essence of reality itself. He is said to have

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“This text has been suppressed due to author restrictions”

summed this up in the famous claim that “everything flows” (panta rhei):” We step and do not step into the same river,” he wrote, “we are and we are not.” According to Plutarch, a later commentator:

For it is not possible to step twice into the same river, according to Heraclitus, nor to touch anything twice: due to the velocity of its change, the thing scatters and collects itself again—or rather, it does not come together and depart, approach and withdraw at one time and then at another, but instead does all this simultaneously.

Constant Change. The constantly flowing water of a stream always makes it a different stream from the one into which we just stepped. For that matter, we ourselves also participate in change—our cells, for instance, are constantly dying and being regenerated—so that even the one who steps into the stream is different from the one who stepped there a moment ago. This approach would seem to make any notion of a fixed and permanent reality quite impossible.

Logos. At the same time, however, Heraclitus also insisted on a single unifying principle behind or beneath or within that constant flux. He called this principle the Logos—a term that embraces a range of meanings, from “word” or “account” to “reason,” “ratio,” and “rationality”—and described it as a kind of balance that underlies and also controls all change. Although he identified the Logos with the element fire, it is unlikely that Heraclitus thought of it as a material substance, like the water and air of the Milesians. Fire instead offered a brilliant metaphor for the constantly changing, constantly identical world: “The cosmos . . . was always and is and shall be an ever-living fire kindled in measures and extinguished in measures.” The reference to measures once again points to an abiding Greek belief in the ultimate orderliness and measurability of the universe. Beneath or behind or within all change, the Logos remains constant.

The Senses. On the epistemological problem of knowledge—How exactly can one know what is real?—Heraclitus implied that the senses are untrustworthy witnesses that must be brought under the control of the rational mind. After all, how else except by reasoning can one discover the invisible Logos concealed by the world’s apparent flux?


In his poem On Nature (fifth century b.c.e.), Empedocles draws an analogy to a common implement from daily life in the ancient world—the klepshudra or “water-catcher”—to explain how liying things breathe:

Everything breathes in and out All creatures have bloodless vessels in their flesh, extending over the surface of the body, and the skin is perforated with pores at the mouths of those vessels, keeping the blood inside but cutting an easy route for air to pass. When the liquid blood moves away from there, the air bubbles in with a violent surge; and when the blood rushes back, the air is pushed out again. It is just as when a girl plays with a bright brass kkpshudm. When she puts her beautiful hand over the mouth of the pipe and dips it into shining water, no liquid enters; instead, the air trapped within presses against the many holes and keeps it back, until she uncovers the thick stream. Then, as the air withdraws, an equal amount of water enters. Likewise, when the bronze implement is filled with water and her hand blocks the mouth, the outer air pushes inwards and holds the water back … until she removes her hand. Then … as air rushes in, an equal amount of water rushes out. So too in the body, when the blood rushing through the limbs moves back and inwards, a stream of air immediately and swiftly rushes in; but when the blood surges up again, an equal quantity of air is breathed back inside.

Parmenides . Far more radical, however, was the view of the next major thinker, Parmenides, born around 515 b.c.e. in the southern Italian city of Elea. For Parmenides, pure logic alone pointed the way to a truth that completely contradicted every shred of evidence our senses can provide. His main argument, rigorously abstract, is preserved in a poem called The Way of Truth. One of its chief aims is to deny that reality could ever be subject to change. The basic argument can be summarized in four points:

  1. Whatever is, is—and if it is, it is impossible for it not to be;
  2. There was never a time when it was not, because then it would have been nonexistent, and “what is” can never come from what is not, since by definition “what is not” has no reality;
  3. Therefore, “what is” must have always been;
  4. If this is true, nothing can ever come into being at all.

A Uniform Whole. The upshot of these dense and knotty claims is that reality always was, is, and will forever be the same. Despite everything our senses report, it is actually static and eternal. There is no coming-to-be or passing-away. Change is an illusion, then: nothing is really born, grows, or dies. Parmenides went even further to claim that reality is perfectly homogeneous—that is, it has no parts, but is instead a single, uniform whole. This approach means that no distinct things exist at all, despite the fact that the evidence of our senses insists on quite the opposite.

Deception . Parmenides’ Way of Truth is a startling tour de force. It utterly rejects the senses and relies on reason aided only by the new science of logic. This argument marked both a starting point and a challenge for all later fifth-century thought. Logic seemed to demand that his reasoning about the true nature of reality be accepted, or at least that all other claims about reality had to have the same logical structure. Fundamental reality must indeed be permanent and unchanging. Yet, as a result, our five senses are not only untrustworthy but even deceptive, since they present us with a view of the world that, on Parmenides’ terms, is totally false. Each of the thinkers who came after him were forced to confront this problem and work out some way of solving it.

Eleatics . On the one hand, philosophers such as Zeno of Elea and Melissus of Samos, both of whom lived around 450 b.c.e. and are collectively known as Eleatics, further refined the tools of logic to support Parmenides. Zeno in particular is

famous for a series of logical paradoxes, all of which construct rigorously logical arguments to prove something that completely contradicts intuition and experience. Among the most famous and familiar is the paradox that denies that an arrow can traverse a given space, from A to B, because it would first need to cross an infinite number of fractions of that distance—one-half, one-quarter, one-eighth, one-sixteenth, and so on—in a finite amount of time. Zeno’s conclusion, of course, is that motion is logically absurd.


Tried and convicted of impiety in an Athenian coitt, Anaxagoras spent the remaining years of his life in, exile. The following passage {from the third-century c.e. theologian Hippolytus) records some of the theories that might well have provided the prosecution with ammunition for its case against the philosopher.

The earth (be thinks) is flat in .shape, and stays, suspended from where it is because of its size, because there is no void and because the air, which is very strong, keeps the earth, afloat on it… The sun, the moon, and all the stars are red-hot stones which the rotation of the aithêr carries round with it. Beneath the stars are certain bodies, invisible to us, that are carried around with the sun and moon. We do not Feel the heat of the stars because they are so far from the earth. Moreover, they are not as hot as the sun and occupy a colder region. The moon is beneath the sun and nearer to us. The sun is larger than the Peloponnese. The moon has no light of its own but derives it from the sun…. Eclipses of the moon are due its being screened by earth or, sometimes, by the bodies beneath the moon; eclipses of the sun, to screening by the moon.

Source: Geoffrey Stephen Kirk and John Earle Raven, The Presocratic Philosophers: A Critical History with a Selection of Texts (Cambridge: Cambridge University Press, 1957).


Patricia Curd, The Legacy of Parmenides: Eleatic Monism and Later Presocratic Thought (Princeton: Princeton University Press, 1998).

Charles H. Kahn, The Art and Thought of Heraclitus: An Edition of the Fragments with Translation and Commentary (Cambridge & New York: Cambridge University Press, 1979).

Alexander Mourelatos, The Route of Parmenides: A Study of Word, Image, and Argument in the Fragments (New Haven: Yale University Press, 1970).

Wesley Salmon, comp., Zeno’s Paradoxes (Indianapolis: Bobbs-Merrill, 1970).

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