This post takes a closer look at “The 2,500-Year-Old Argument About What’s Real.” Here, I dig into what Parmenides actually argued, what Heraclitus proposed, and where experts still debate. I think this old argument still shapes how we talk about the self today.

Let’s begin with something simple. An unstrung bow is just a curved stick and a cord. When you string it, each part pulls on the other, and both are changed by the tension. On the reading I’ll follow, Heraclitus thought the world is more like the strung bow than two separate things. To see why this matters, it helps to look at the philosopher often seen as his opposite.

What Parmenides Actually Argued

Parmenides wrote a single poem in epic verse, of which about 160 of perhaps 800 lines survive. A goddess teaches him that What Is must be “ungenerated and deathless, whole and uniform, and still and perfect.” It cannot come to be, since it would have to come from what is not, and what is not can be neither said nor thought.

The textbook version stops there and calls Parmenides a strict monist: exactly one thing exists, and change, plurality, and even our own selves are illusions. John Palmer’s survey of the scholarship lists at least five ways of reading the poem, and notes that the strict-monist reading is less common than it once was. On the modal reading Palmer himself defends, Parmenides was the first philosopher to distinguish rigorously what must be, what must not be, and what is but need not be. The changing things of ordinary experience are real on this view, only contingent, and so unfit objects for the kind of understanding that “does not wander.” Parmenides becomes a “generous” monist: one thing must be, and many things are without having to be.

This question still matters in modern philosophy. Jonathan Schaffer argues for “priority monism,” the idea that the whole universe comes before its parts. He gives monism a pedigree running from Parmenides, Plato, and Plotinus to Spinoza, Hegel, and Bradley. In a note, though, he counts Parmenides as an “existence monist,” holding the stricter view that there is “one and only one actual concrete object.” Schaffer even begins one of his main papers with a quote from Heraclitus: “Listening not to me but to the Logos it is wise to agree that all things are one.” He doesn’t comment on it, but the choice is telling. Keep that in mind.

One River Fragment, Not Three

The famous river saying comes from Plato. In his dialogue Cratylus, Plato reports: “Heraclitus, I believe, says that all things pass and nothing stays, and comparing existing things to the flow of a river, he says you could not step twice into the same river.” That is Plato’s paraphrase, not a quotation from Heraclitus.

Plato’s reading is easy to state. Everything is always changing, so nothing can be met twice, not even a river. Plato drew a further conclusion: if the things we perceive never hold still, they cannot be known. He seems to have taken this reading from Cratylus, a later follower of Heraclitus, who pushed it further and said you cannot step into the same river even once. Plato then used it as his picture of the changing world of the senses.

Heraclitus’s own words survive only because later ancient writers quoted them, and three river sayings come down to us that way. One says that other waters flow on those who step into the same rivers (B12). One says we both do and do not step into the same rivers (B49a). One says you cannot step twice into the same river (B91), much as Plato has it. Following G. S. Kirk and Miroslav Marcovich, Daniel Graham argues that only B12 is genuine. The second begins with the same three words, but in a different Greek dialect from Heraclitus’s, and its second half doesn’t connect to the first. The third is “patently a paraphrase.”

Here is B12 in Graham’s deliberately literal translation: “On those stepping into rivers staying the same other and other waters flow.” The odd word order is on purpose. In the Greek, “the same” can go with the rivers or with the people stepping in, and on Graham’s reading Heraclitus meant both.

In the first reading, Graham suggests, the changing waters do more than just flow through the river. They “actually constitute the rivers, and maintain them as the same rivers.” If the water stopped, the river would turn into “a lake or a dry streambed.” In the second reading, which Graham takes from Charles Kahn, the people stepping in stay the same “precisely by confronting the changing waters, or more broadly, their changing surroundings.” I find this second reading most interesting for this project. It shows a self that keeps its identity by engaging with a changing world, not by staying separate from it.

Plato’s reading still has defenders, but it is, in Graham’s words, “no longer the only reading.” Its most careful modern descendant comes from Jonathan Barnes. As Graham summarizes him, Barnes reads Heraclitus as a material monist, for whom all things are modifications of fire, holding two further principles. Flux: “everything is always flowing in some respects.” The unity of opposites: “every pair of contraries is somewhere coinstantiated; and every object coinstantiates at least one pair of contraries.” Read that precisely, the unity of opposites entails contradictions. Barnes concludes that Heraclitus, writing before the development of logic, violates its principles and makes knowledge impossible; Heraclitus, he suggests, “might well have failed” to see the problem.

If Barnes is right about opposites, then the unity of opposites is a logical mistake, not a real structure of relations, and the relational view of Heraclitus does not hold up. Graham answers on two fronts. On opposites, he points out that Heraclitus knows the qualifiers Barnes says he drops. Sea water is “drinkable and healthy” for fish and “undrinkable and harmful” for men, and sleep and waking are both in us, “but not at the same time.” On the larger picture, he argues that flux and monism pull against each other. If everything is really fire, then nothing truly comes into being or disappears, and all change is just on the surface; Heraclitus would be a philosopher of one unchanging substance in disguise. A reading that avoids those contradictions is, he argues, the better one. Graham says Heraclitus’s paradoxes are “provocative heuristic devices”; we do not have to take them literally. I generally agree with Graham, though I know this is just one side of an ongoing debate.

Account and Order

Heraclitus’s word for the order behind measured change is logos, though, as we’ll see, scholars disagree about just what the word names. His book opened with a warning: “Of this Word’s being forever do men prove to be uncomprehending, both before they hear and once they have heard it.” Two senses are already at work in that sentence. The logos is something you can hear, like a speech. It also exists “forever,” whether anyone understands it or not. Heraclitus presents himself less as the author of a theory than as a spokesman for something independent of him: “Having harkened not to me but to the Word (Logos) it is wise to agree that all things are one.”

To see how one word could carry both senses, it helps to know what it meant before him. Robert Fowler’s study of the two old Greek words for speech, mythos and logos, is the clearest guide. In the earliest Greek poetry, mythos was the weighty word. It named a pronouncement backed by the standing of whoever made it: a warrior’s words, the Muses speaking to the poet Hesiod. Fowler calls it “speech with accoutrements,” meaning the words plus the speaker and the occasion. Logos was the plain, everyday word for speech of any kind. In the oldest texts, Fowler reports, drawing on Lincoln, it often named soft, charming talk, the kind that could also deceive.

That ranking later reversed, and Fowler explains why. A mythos was only as trustworthy as the person who spoke it. As the Greek cities began to question the authority of powerful men, their pronouncements lost the presumption of truth. Logos, the word for what was said and not who said it, became the word for an account judged on its own merits. By Plato’s time, a mythos was a story that might be false and a logos was a reasoned account. Fowler dates that familiar contrast between myth and reason to the middle of the fifth century BCE, a generation or two after Heraclitus.

Heraclitus was part of this shift and made logos central to his thinking. Fowler says that for Heraclitus, logos “meant both the rational order of the world and one’s account of it.” The word refers both to the act of speaking and understanding, and to a clear, accurate account of reality. Imagine a good map of a river. The map is an account, and the river’s path is the order it shows. When the account is accurate, the two match so well that one word can describe both the pattern you follow and the pattern itself.

Not every scholar reads the word this way. Mark Johnstone argues that Heraclitus “denotes by the term ‘logos’ neither his own discourse nor a cosmic law, but rather the world’s orderly and intelligible … presentation of its nature to us throughout our lives.” On that reading, logos is the way the world shows itself as orderly and understandable, not a law standing behind it. The two readings disagree about what the word names. Both tie the order of the world to our understanding of it, which is the point this project cares about.

Heraclitus, in Fowler’s phrase, “threw logos into the highest possible relief,” and later thinkers either built on his ideas or pushed back against them. The biggest break came with the Sophist Protagoras, who said every question has two opposing logoi. That is very different from Heraclitus’s idea of a single logos. As I see it, the main point is this: understanding the world is not about making up your own version of it. It is about matching your understanding to an order that already exists.

The logos is also common. “Although this Word is common, the many live as if they had a private understanding” (B2). “Speaking with sense we must fortify ourselves in the common sense of all, as a city is fortified by its law” (B114). Enrique Hülsz Piccone notes that the Greek of that second fragment plays on xunôi, “the common,” and xun nooi, “with understanding”: the common becomes the ground of intelligent speech.

A word of caution before using this idea for an ethics of dialogue. In the city, Hülsz points out, the common is the law, since nomos is a kind of logos, and he calls this way of thinking poco democrática (rather undemocratic). Heraclitus believed that one good person is worth ten thousand ordinary people. His idea of the “common” is an order to follow, not a discussion among equals.

Opposites That Stay Different

The river is just one example of a bigger idea: opposites that are linked together. “As the same thing in us are living and dead, waking and sleeping, young and old. For these things having changed around are those, and those in turn having changed around are these” (B88). Sleep and waking both exist in us, just not at the same time. As Graham puts it, the opposites are “interconnected, but not identical.”

“A road up and down is one and the same” (B60). Celso Vieira uses this idea to model change: two opposites joined by a single path that goes both ways. The opposites need that path to exist, but their union “cannot result in an homogeneous whole, for it would make the change impossible.” The difference between them has to remain for the union to work.

Then the bow. In Richard Neels’s translation, B51 reads: “They do not understand how being at variance with itself it agrees with itself: back-turning structure [palintropos harmoniê] as of a bow or a lyre.” The instrument works because its parts pull against each other. A working bow, Neels points out, depends on its parts “but also … on their relationship to one another,” and the parts depend on that relationship in turn, since the string’s tension is set by the stave and the stave’s by the string.

A Cosmos With Nothing Basic

Neels applies the bow idea to the whole cosmos using B10: “Collections: wholes and not wholes; brought together, pulled apart; sung in unison, sung in conflict; and from all things one and from one all things.” He argues that nothing in Heraclitus’s cosmos is fundamentally basic. The parts support each other, and the cosmos and its parts exist in “a relation of reciprocal determination.” Neels calls this “cosmic interdependence,” presents it as a new interpretation, and directly contrasts it with Schaffer’s view. Where Schaffer opened with “all things are one” (B50), Neels answers with B10: “from all things one and from one all things” shows, he argues, that the whole and the parts depend on each other, with neither coming first.

Hülsz reaches a similar point by looking at the logos: Heraclitean unity is not just simple identity but conjunción o comunidad (conjunction or community), a dynamic unity that includes opposition and tension.

Not everyone reads Heraclitus this way. Vieira, in a later paper, finds Graham’s process reading of opposites convincing but argues that Heraclitus’s view leads to real contradictions during change, and that “we should not start explaining away the occurrence of objective contradictions.” David Shaw thinks the unity of opposites is either mistaken or too vague “to be regarded as a serious proposition about the nature of the universe.” Shaw adds, though, that the idea of managing tension, “for the sake of the usefulness of a bow or a lyre,” is useful in practice. The fragments do not settle the issue.

Where Whitehead and Buber Pick It Up

Some later thinkers take up Heraclitus by name. Alfred North Whitehead starts his chapter on process in Process and Reality with “all things flow,” the traditional saying attributed to Heraclitus, which he calls “the first vague generalization” of human intuition. Later in the book, he says that mathematical physics turns Heraclitus’s “All things flow” into its own language, where it “becomes, All things are vectors.”

For this project the most important reader is Martin Buber. In “What Is Common to All,” Buber builds on the saying that people who are awake share one world while each sleeper turns away to a world of his own. He names “three basic concepts of Heraclitus: the concept of the common, of the logos, and of the cosmos.” He gives the logos its double character in his own terms, “the wedding between meaning and speech,” and says it “does not attain to its fullness in us but rather between us.” Heraclitus’s teaching, he writes, “knows no other harmony than that which arises out of its tensions,” and when people work together in the service of the logos, “out of the extremest tension … arises ever anew the harmony of the lyre.”

Then Buber goes a different way. Having “summoned the help of Heraclitus,” he writes: “But now he parts from us in our need or we part from him.” For Heraclitus, what he calls the common “has nothing that is over against it as such: logos and cosmos are, to him, self-contained; there is nothing that transcends them.” Buber doesn't say in which respect Heraclitus falls short, Maurice Friedman notes, but Friedman concludes that the ground of Buber's view is religious: “Real existence as a We is not possible in a self-contained cosmos, but only in ever renewed dialogue with what is over against us.” In this essay, Buber builds on Heraclitus’s common and then departs from it.

My Take

On the strict reading, Parmenides said that true unity means getting rid of the many. Heraclitus, as I see it, said the opposite: that unity works when it holds together many things in tension, without dissolving or scattering them. I don’t think he proved this, and I don’t think the experts who study him all agree he meant it. Still, the images of the bow, the river, and the road are hard to forget once you see them as he did.

What affects me most is Buber's correction. A cosmos held together by its own tensions is beautiful, but it is also closed; nothing beyond it can address it. Buber's answer is a We that stands before God. Mine, as a clinician, starts closer to home: the relational self I care about needs another person who stands across from me and responds. It is the other person who encounters us in the difference of our lived daily experience that calls forth our potential for becoming, much as the bow calls forth the potential of the string. I don’t think the question of the one and the many has ever gone away. We have just found better ways to talk about it.

Revised October 22, 2026. This post has been updated to correct several statements about its sources and to quote the original texts more closely. It also expands the discussion of the river fragments and of what logos meant before Heraclitus.

Go Deeper

  • “Heraclitus” by Daniel W. Graham, Stanford Encyclopedia of Philosophy (free online): the clearest guide to the river debate and the unity of opposites, with the fragments in translation.
  • “Parmenides” by John Palmer, Stanford Encyclopedia of Philosophy (free online): the five ways of reading the poem, and the case for the “generous” Parmenides.
  • “What Is Common to All” by Martin Buber, in The Knowledge of Man: Buber’s Heraclitus essay, including the moment he parts company with him.

References

Barnes, Jonathan. The Presocratic Philosophers. Rev. ed. London: Routledge & Kegan Paul, 1982. Chap. 4, “The Natural Philosophy of Heraclitus.” Quoted as reported in Graham, “Heraclitus,” and in Neels, Opposites and Explanations in Heraclitus (which cites the 1979 edition).

Buber, Martin. “What Is Common to All.” Translated by Maurice Friedman. In The Knowledge of Man: Selected Essays, edited by Maurice Friedman, 79–99. Atlantic Highlands, NJ: Humanities Press International, 1988.

Fowler, Robert L. “Mythos and Logos.” Journal of Hellenic Studies 131 (2011): 45–66.

Friedman, Maurice. “Introductory Essay.” In Martin Buber, The Knowledge of Man: Selected Essays, 1–48. Atlantic Highlands, NJ: Humanities Press International, 1988.

Graham, Daniel W. “Heraclitus.” Stanford Encyclopedia of Philosophy (Winter 2023 Edition).

———. “Heraclitus as a Process Philosopher.” Philosophy Study 2, no. 1 (2012): 1–8.

Hülsz Piccone, Enrique. “La unidad de la filosofía de Heráclito.” Tópicos 28 (2005): 13–49.

Johnstone, Mark A. “On ‘Logos’ in Heraclitus.” Oxford Studies in Ancient Philosophy 47 (2014): 1–29. Quoted in Neels, Opposites and Explanations in Heraclitus.

Neels, Richard. “Cosmic Interdependence: Heraclitus on Grounding.” Ancient Philosophy Today: Dialogoi 3, no. 1 (2021): 30–53.

———. Opposites and Explanations in Heraclitus. PhD diss., McMaster University, 2018.

Palmer, John. “Parmenides.” Stanford Encyclopedia of Philosophy, rev. 2025.

Schaffer, Jonathan. “Monism: The Priority of the Whole.” Philosophical Review 119, no. 1 (2010): 31–76.

Shaw, David. “On Misunderstanding Heraclitus: The Justice of Organisation Structure.” Philosophy of Management 18, no. 2 (2019): 157–67.

Vieira, Celso. “Heraclitus, Change and Objective Contradictions in Aristotle’s Metaphysics Γ.” Rhizomata 10, no. 2 (2022): 183–214.

———. “Um modelo para a mudança em Heráclito.” Codex 2, no. 2 (2010): 118–36.

Whitehead, Alfred North. Process and Reality: An Essay in Cosmology. Corrected ed. New York: Free Press, 1978.