Ionian Thinkers

By C.D.C. Reeve | June 1, 2011

Thales, Anaximander, and Anaximenes were from Miletus, which is on the Ionian coast of Asia Minor. Their great successor Heraclitus was from Ephesus, which is on the same coast. Together these Ionian thinkers of the sixth and late fifth centuries brought about one of the most significant revolutions we know of, one that set the civilized world on a path it has followed, with minor and not so minor deviations, ever since. What they did, to put it boldly and rather simply, was to invent critical rationality. For the theories they advanced, whether on the nature and origins of the cosmos or on ethics and politics, were not offered as gospels to be accepted on divine or human authority or, like Hesiod’s cosmology, on the authority of the Muses, but as rational constructions to be accepted or rejected on the basis of evidence and argument. Every university and college, every intellectual discipline and scientific advance, every step towards freedom and away from ignorance, superstition, and enslavement to repressive dogma is eloquent testimony to the power of their invention. If they had not existed, our world would not exist.

Of these thinkers, Thales was the first. His reputation in antiquity was immense. He was one of the fabled Seven Sages (Solon was another). He is credited with being able to predict solar eclipses and with determining the height of the pyramids by measuring the length of their shadows. Whether he wrote anything is unknown. If he did, no genuine fragment of it has survived. But despite the fact that we possess none of Thales’ original words, we do know that he held that everything is water, or something to that effect.

The first thing to notice about this claim is that it says that there is really only one thing—water—and that everything else is in some way made up of or built out of it. We don’t know just why Thales assigned such a fundamental role to water. Perhaps, as Aristotle claims, he noticed that water is essential in various ways to the existence of living things (Metaphysics, 983b22–27), or that water alone exists naturally as a solid, liquid, and gas, and so might be the fundamental stuff from which all things were made. If Thales did think in either of these ways, his doctrine is a prototype of many fundamental scientific doctrines. It is based (no doubt somewhat loosely) on evidence and argument, and it suggests that a single thing underlies and explains the apparent diversity of phenomena. Modern scientists who claim that everything is mass-energy or that the four-dimensional space-time continuum is the only real thing are heirs to Thales.

Two ancient stories about Thales are worth repeating, because of the somewhat different light they cast on early philosophy. The first is recounted in Plato’s Theaetetus:

Once while Thales was gazing upwards while doing astronomy, he fell into a well. A clever and delightful Thracian serving girl is said to have made fun of him, since he was eager to know the things in the heavens but failed to notice what was in front of him and right next to his feet (174a4–8).

The second story might be thought of as Thales’ slightly revengeful response to the servant-girl. It is found in Aristotle’s Politics:

The story goes that when they found fault with him [Thales] for his poverty, supposing that philosophy is useless, he learned from his astronomy that there would be a large crop of olives. Then, while it was still winter, he obtained a little money and made deposits on all the olive presses both in Miletus and in Chios. Since no one bid against him, he rented them cheaply. When the right time came, suddenly many tried to get the presses all at once, and he rented them out on whatever terms he wished, and so made a great deal of money. In this way he proved that philosophers can easily be wealthy if they desire, but this is not what they are interested in (I 11 1259a9–18).

The moral of the story is that apparently arcane knowledge can have important practical uses, so that philosophy can help us to live well, and that we neglect it at our peril (see Plato, Republic 487d ff.).

Anaximander was a younger contemporary of Thales. Only a few words of his writings have survived, but ancient sources give us a vivid idea of their astonishing scope. They contained a cosmogony, or account of the origins of the cosmos; an account of the origins of life; astronomical, meteorological, and biological speculations; and a map of the known world. Our primary interest is in Anaximander’s most general explanatory doctrine, but a brief glimpse at two of his other views shows what a daring thinker he was.

The first of these concerns the origin of human beings:

[Anaximander] also declares that in the beginning humans were born from other kinds of animals, since other animals quickly manage on their own, and humans alone require lengthy nursing. For this reason, in the beginning, they would not have been preserved if they had been like this.

Here an observation coupled with an insightful piece of argument leads to a daring hypothesis: Human beings were not made by gods. They came from other animals.

The second piece of Anaximandrian speculation concerns the ancient question of what holds up the earth. Thales seems to have held that the earth is floating on water, “as if,” Aristotle witheringly comments, “the same question did not arise . . . for the water supporting the earth” (De Caelo 294a32–23). Aware, perhaps, of this defect in Thales’ answer and in other similar ones, Anaximander proposed a different kind of answer altogether. He declared that

the earth is at rest on account of its similarity. For it is no more fitting for what is established at the center and equally related to the extremes to move up rather than down or sideways. And it is impossible for it to make a move simultaneously in opposite directions. Therefore, it is at rest of necessity.

In other words, the earth doesn’t move, not because it’s held up by something else, but because there’s nothing to cause it to move in one way rather than another. The cleverness of this answer is obvious, since it gets around the kind of criticism that Aristotle uses against Thales.

I turn now to Anaximander’s fundamental doctrine:

Of those who declare that the first principle is one, moving, and indefinite, Anaximander . . . said that the indefinite was the first principle and element of things that are . . . He says that the first principle is neither water nor any other of the things called elements, but some other nature which is indefinite, out of which come to be all the heavens and the worlds in them.

The fundamental stuff out of which everything else is made or comes to be isn’t any of the four recognized elements—earth, water, fire, and air (or dry, wet, hot, and cold)—but a fifth thing, the unlimited. Why? According to Aristotle (Physics III 5 204b22–29), Anaximander argued, “If everything is water, then everything must have the properties of water. But not only do some things lack these properties, some even have properties that are the opposites of those possessed by water: Earth isn’t wet, it’s dry. Since nothing can be both wet and dry, how can dry earth just be some form of wet water? How can what just is wet water become dry?” This is a powerful argument for thinking that if there is a single stuff of which all things (including the elements) are made, it cannot have any definite characteristics of its own. It must be indeterminate in quality.

More significantly, this Anaximandrian argument is a telling criticism of his predecessor, Thales. Consequently, it’s a good example of the critical rationality I praise the Greek philosophers for inventing. Anaximander didn’t accept Thales’ doctrines on his authority or, as we are asked to accept Hesiod’s cosmogony, on the authority of the Muses; rather, he submitted them to rational scrutiny, modifying those that failed to pass muster and accepting only those that did. In the Nicomachean Ethics, just as he is about to criticize the doctrines of his own teacher, Plato, Aristotle recommends this as the appropriate attitude for a philosopher to take to his forebears:

It presumably seems better, indeed only right, to destroy even what is close to us if that is the way to preserve the truth. And we must especially do this when we are philosophers, [lovers of wisdom]; for though we love both the truth and our friends, piety requires us to honour the truth first (I 6 1096a).

Paradoxically, then, it is by destroying Thales’ doctrines, rather than by accepting them unquestioningly, that Anaximander reveals himself as Thales’ true heir.

In addition to criticizing Thales’ doctrines, Anaximander also made an important suggestion about what causes the elements to interact and give rise to the things we see around us:

The things that are perish into the things out of which they come to be, according to necessity, for they pay penalty and retribution to each other for their injustice in accordance with the ordering of time.

His idea seems to be that elements, conceived of as opposite powers (dry/wet, hot/cold), struggle with one another, with sometimes one gaining the upper hand, sometimes another. When this happens the balance or equilibrium of the cosmos is disturbed: one opposite has gained “unjustly” at the expense of another, and must of necessity—or because of the laws governing the cosmos—pay reparation to it in due course, so that equilibrium is restored once more. No doubt this is, indeed, “rather poetical,” as Simplicius puts it, but it certainly shouldn’t be dismissed on that account. For it contains the fundamentally important notion that the natural world is governed by necessity (by law) not by the arbitrary whim of the gods. Many good and fruitful theories start their lives as metaphors.

Anaximander’s follower, Anaximenes, developed Anaximander’s account of the elements and introduced significant economies into it. In Anaximander’s cosmology, there are four elements (earth, water, fire, and air) as well as the somewhat mysterious indeterminate stuff, whose relation to them is not fully explained. Thus Anaximander has five fundamental things in his ontology. Anaximenes seems to have realized that the unlimited was unnecessary baggage, that one of the elements could play its role. He claimed that air is the fundamental principle of everything, and that earth, water, and fire are simply air which is to different degrees either rarefied or condensed. Earth is very dense air; fire is very rarefied air:

The form of air is the following: when it is most even, it is invisible, but it is revealed by the cold and the hot and the wet, and movement. ... For when it is dissolved into what is finer, it comes to be fire, and on the other hand air comes to be winds when it becomes condensed. Cloud results from air through felting, and water when this happens to a greater degree. When condensed still more it becomes earth, and when it reaches the absolutely densest stage it becomes stones.

Thus Anaximenes’ theory is at once simpler and more complete than Anaximander’s. It needs only one thing—air—where Anaximander’s needs five. Moreover, it explains in a straightforward way what Anaximander leaves mysterious: how the one fundamental stuff can give rise to the other elements that appear in the world. This makes it a better theory and another good example of critical rationality—or a critically rational tradition—in operation.

The next step in this line of argument was taken by Heraclitus of Ephesus, a consummate thinker and writer, if a rather difficult one. In the following fragments, he speaks of the birth of one element as the death of another.

It is death to souls to become water, death to water to become earth, but from earth comes water and from water soul.

Fire lives the death of earth and air lives the death of fire, water lives the death of air, earth that of water.

If we set out the claims they make in a table, we can see that they describe the series of transformations already familiar to us from Anaximenes:

Death of  Birth Of
Fire Air
Air Water
Water Earth
Earth Water
Road A (Downward Road) Road B (Upward Road)


Notice that the transformations are cyclical. When they are complete, what started as fire ends up being fire again.

Now, two questions naturally arise about this cycle of transformations: What causes it to occur? And what happens to fire, for example, when it becomes air? Anaximander’s answer to the first question is that strife between the opposites causes the transformations on Road A (the downward road), and that justice causes the transformations on Road B (the upward road). Heraclitus adopts this answer, but sees that it can be simplified without loss of explanatory power. He sees that because the transformations are cyclical, we do not need two forces—strife and justice—to drive them, but only one. Hence he tells us that “justice is strife,” that “the road up and the road down are one and the same,” and that “the beginning and end are common on the circumference of a circle.” Thus the force that transforms fire into air also transforms air back into fire. (This Heraclitean criticism of Anaximander is a model of critical scientific rationality at work. Physicists like Steven Weinberg or Murray Gell-Mann, who look for Grand Unified Theories in which gravitational, electromagnetic, and weak and strong forces are unified, are heirs to Heraclitus.)

To see how Heraclitus answered the question about what happens to fire when strife causes it to become air, we must begin, as he surely did, with Anaximenes. In Anaximenes’ view, elements change into one another by becoming more rarified or more condensed. But this account is uneconomical because it introduces a new primitive notion—rarifaction/condensation—over and above the original four elements. Heraclitus seems to have noticed this defect in Anaximenes’ theory and tried to rectify it. In his view, all that happens when fire is transformed into air is that it dies down. Thus Road A (the downward road) is the progressive dying down of fire and Road B (the upward one) is its progressive rekindling. Thus only fire “being kindled in measures and being extinguished in measures,” is needed to explain how strife (justice) causes the elements to be transformed into one another, so that their cyclical transformations are simply “the turnings of fire.”

But why does Heraclitus assign such a fundamental role to fire rather than to air or one of the other elements? Why does he identify the cosmos with “ever-living fire” rather than with ever-living air or ever-living water? Why is Road A the progressive dying down of fire rather than the progressive drying of the wet? To see a possible answer, we need to return to the first question we raised: What causes the elements to be transformed into one another? Anaximander’s answer was strife and justice. Heraclitus simplifies this to a single causal agent: strife. But Anaximander does not tell us why the elements strive with one another in the first place. Strife enters the Anaximandrian cosmos, as it were, from the outside; it is something extrinsic to, or over and above, the unlimited and the four elements. Strife, however, is intrinsic to a cosmos of fire. For fire is “want and satiety”: it exists only when striving with what it is trying to burn; it simultaneously wants or needs fuel and is becoming hungry through consuming it. It is this dynamic feature, possessed by none of the other opposites, that most likely led Heraclitus to assign priority to it. It enables him to “reduce” strife to fire (since if fire exists so must strife) just as he has already reduced justice to strife.

One final theoretical advantage of fire deserves to be mentioned. Fire exists through striving with its fuel, but its striving is law-governed or measured:

Earth is poured out as sea, and is measured according to the same ratio (logos) it was before it became earth.

After all, the size or heat of fire is proportional to the amount of fuel being consumed. Thus if fire is the fundamentally real thing, this offers an explanation of the order observed in such things as the seasons and the rising and setting of the sun.

There is no doubt that the theory that results from these reductions is vastly more successful than any of the theories of Heraclitus’ predecessors. It is also fundamentally different in kind. Heraclitus doesn’t tell us that the cosmos and all its contents are fundamentally fire, he tells us that they are fire “being kindled in measures and being extinguished in measures.” This emphasizes the fact that what is fundamentally real for Heraclitus is not a static stuff to which change and activity are extrinsic, but a law-governed process or activity. Heraclitus differs from his predecessors, then, not simply in choosing fire rather than water, air, or the unlimited as his primary stuff, but in choosing law-governed change over static stability as being more fundamentally real. In the worlds of Thales, Anaximander, and Anaximenes, change depends on stability; in Heraclitus’ world, stability depends on change: “Changing, it rests.”

Heraclitus’ powerful vision of the world exerted enormous influence over his successors, who tried in various ways to destroy, criticize, modify, and augment it. But it is not his theory so much as the spirit in which he offers it, that I have wanted to emphasize. He wasn’t the first to theorize in that spirit, he was part of a tradition of critical rationality that already existed. But he was the first to give explicit voice to it:

Listening not to me but to the logos it is wise to agree that all things are one.

This is the injunction that all the subsequent Greek philosophers follow. As students of Greek philosophy, it is an injunction we must strive to follow ourselves. If we do, we will become what so many Greek philosophers thought was the best thing to be: critically rational human beings.

C.D.C. Reeve taught at Reed for 25 years (1976–2001) and is now Delta Kappa Epsilon Distinguished Professor of Philosophy at the University of North Carolina at Chapel Hill. He works primarily in ancient Greek philosophy, especially Plato and Aristotle. His books include Philosopher-Kings (1988), Socrates in the Apology (1989), Practices of Reason (1992), Substantial Knowledge (2000), and Love’s Confusions (2005). He has translated Plato’s Cratylus (1997); Euthyphro, Apology, Crito (2002); Republic (2004); and Meno (2006), as well as Aristotle’s Politics (1998). His new book, Immortal Life: Action, Contemplation, and Happiness in Aristotle, will soon appear from Harvard University Press. A related book, Aristotle on Practical Wisdom: Nicomachean Ethics Book VI, Translated with Introduction, Analysis, and Commentary, is in the works.

These classic Hum lectures were selected by Peter Steinberger [political science and humanities 1977–].

Further Reading

Patricia Curd, ed., A Presocratics Reader (Indianapolis: Hackett, 1996)

Charles Kahn, The Art and Thought of Heraclitus (Cambridge: Cambridge University Press, 1979)

Karl Popper, “Back to the Presocratics,” in his Conjectures and Refutations (London: Routledge, 1963)