What stays the same when things change?

A cup that was not there

A potter shapes a lump of clay into a cup. Something new now exists, yet she has not made it out of nothing: the clay was there already. So we can say both that the cup has come into being and that its material has continued, and the two statements answer different questions.

What, then, has changed, and what remains? And what would count as explaining the difference? To ask about nature here is to ask what things are and how they behave. Change puts both questions under pressure: how can we explain what a thing is while it is becoming something else?

We now leave Han Feizi’s offices and rules for two early Greek thinkers whose arguments turn change into a puzzle. Moving from China to Greece in this course implies no historical influence between the two conversations. Nor does it mark the point where reasoning begins: the earlier modules were already full of sustained argument, and Greek inquiry has no monopoly on it.

Reading words inside other books

Heraclitus of Ephesus, on the coast of what is now Turkey, and Parmenides of Elea, in southern Italy, were active around the beginning of the fifth century BCE. Neither man’s work survives complete, so we depend on passages that later writers quoted or described. [1]

That makes it important to know what kind of passage we are reading. A fragment here means words that editors judge to be a quotation from a lost work; it need not be a torn piece of papyrus. A report, also called a testimonium, tells us what another writer says a thinker held. The same later book may preserve both, but they are different kinds of evidence: a quotation offers evidence of wording, while a report offers someone’s account of a view.

Even a quotation calls for judgment. Where does it begin and end, and why did the later author use it? The specialists Jaap Mansfeld and David Runia show that collections of earlier views were organized for particular philosophical purposes, so a source can preserve precious evidence while also shaping how we meet it. [2]

A river that continues by changing

Heraclitus’s river fragment, conventionally numbered B12, describes different waters flowing upon people who enter the same rivers. The contrast is the point: the waters differ, while the rivers are called the same. [1]

On one interpretation, a river continues because its water moves. It persists through a process, not by keeping every part unchanged. Daniel W. Graham defends this reading and contrasts it with the stronger claim that nothing stays the same. The fragment allows his reading, though it does not compel every reader to accept it. [3]

The familiar saying that you can never step into the same river twice needs more care. Plato reports such a view in the Cratylus, and Plutarch gives a related formulation much later. To treat either report as the exact words of B12 would hide a real difference, and the difference changes the philosophical question: does change destroy continuity, or can it sustain it? [1] [3]

Order within change

Heraclitus also describes a world of fire kindled and extinguished in measures, and an attunement like that of a bow or lyre. The measures suggest regularity, and the bow and lyre suggest a unity held together by tension. In a strung bow, opposed pulls make a working whole; release the tension and the bow can no longer do its work. That is one way to understand the image, and it does not imply that every conflict is beneficial. [1]

His word logos can mean an account or an explanation. In B1 and B2 he connects it with the way things happen and with something people can share in understanding. If change has an order we can understand, it need not defeat explanation. Yet naming an order is only a beginning: we must still say what the order is and how the evidence supports it. [1]

Parmenides asks what can be thought

Parmenides makes the difficulty sharper. His poem tells of a young traveler who meets a goddess; she teaches him and calls on him to judge by reasoning. Religious imagery and argument share the same poem, and because the demand for reasoning comes from the goddess herself, the poem resists any simple story of myth giving way to reason. [1]

The goddess distinguishes an inquiry into what is from a supposed inquiry into what is not. The second cannot succeed, she says, because what is not can be neither known nor expressed. Being concerns what it is for something to be. We can start with the question of existence, though scholars dispute exactly how the poem uses “is.” Its expression “what-is” names whatever the argument will investigate. [1]

This restriction is a demanding premise, a starting claim about what thought can reach, and its force still needs examining. How does a claim about thinking become a claim about what can happen?

Could being begin?

In fragment B8, the goddess asks where what-is could have come from. It cannot have come from what-is-not, since the earlier restriction rules that out. And if it began from nothing, what could have made it arise later rather than earlier? Nothing would explain why it began just then. Coming into being would require a passage out of what-is-not, and perishing a passage into it, so the argument excludes both. The fragment goes on to describe what-is as continuous and unchanging. [1]

Return to the potter. “There was no cup” does not mean “there was nothing.” There was clay. The example suggests a reply, since something can take on a new form without existence emerging from sheer nonexistence. The reply still owes an account of the new form, though. Has it separated two meanings of “is not”—not being a cup and not existing at all—or merely renamed the difficulty? The question tests one step of the argument; it doesn’t pretend to refute the whole poem.

Scholars disagree about how far the argument reaches. The poem also gives an account of the changing cosmos, and how that account relates to its account of what-is remains disputed. John Palmer surveys the competing readings. Whatever we conclude, we should not reduce the whole poem to a simple denial of everything we see. [4]

Try the distinction

Imagine a fountain that keeps its shape while fresh water continually passes through it. One reader says that its continuity shows how change can sustain something. Another asks what must already exist for the fountain to appear at all. Explain how these two questions differ. Then explain why a later writer’s description of Heraclitus is not automatically a quotation from him.

Read a possible response

One reader asks about persistence, the other about coming into being. The first asks how an ongoing process can stay recognizable while its material changes, which fits the interpretation of Heraclitus explored here. The second asks what coming into being requires: water, a channel and a source of motion already exist, which helps separate forming something from producing being out of nothing, though it does not settle every step of Parmenides’s argument. As for the later writer, a report may preserve an interpretation or a paraphrase, so we need evidence that it quotes Heraclitus before treating its wording as his. Even a quotation leaves questions about context and meaning.

Carry this forward

When someone explains a change, ask what begins, what ends and what the explanation assumes was already there. In the next lesson, Plato’s Socrates brings examination into the Athenian city, and the questions turn personal: what do people mean by living well, and can they explain their confidence?

Sources and limits

[1] Readings in Ancient Greek Philosophy: From Thales to Aristotle, edited by S. Marc Cohen, Patricia Curd and C. D. C. Reeve, fifth edition, Hackett, 2016; ebook ISBN 9781624665943, for the translated fragments of Heraclitus and Parmenides. Patricia Curd is responsible for the Presocratics section, whose translations are by Richard D. McKirahan unless marked otherwise. The following were read:

• Guidance: the “Sources” and notation guidance, pp. 5–6, and the Heraclitus introduction, pp. 19–20.
• Heraclitus: B1–B2, p. 20; B12, B91, B49a and B30, p. 22; B51, p. 23; notes 18–19. B30 is Curd’s translation. B12 is preserved through Arius Didymus, fragment 39.2; B91 through Plutarch, On the E at Delphi 392b; B51 through Hippolytus, Refutation of All Heresies 9.9.2. The anthology marks B49a as disputed and brackets the twice-in-the-river formulation in B91. Note 19 records disagreement over a word in the bow/lyre image.
• Parmenides: the complete supplied section, introduction and fragments B1–B19, pp. 26–30, with notes 22–24. The discussion concentrates on B1–B2, B7 and B8. These four translations are McKirahan’s as modified by Curd. B8 spans pp. 28–29; its argument against coming-to-be is at lines 5–21 on p. 28. Its chief transmitting source is Simplicius, Commentary on Aristotle’s Physics 145.1–146.25 for lines 1–52; the anthology also cites 39.1–9 for lines 50–61.

“B” and its number identify a passage in the Diels–Kranz collection; they are not ancient chapter numbers or a guarantee of authenticity. The ebook’s numbered braces correspond to print pages. Only selected translations and editorial notes were read, not the whole anthology, complete ancient works or Greek manuscripts, and the anthology’s modern ordering does not recover Heraclitus’s original sequence. The manuscript witnesses, the surviving copies used to establish a text, were studied through the editions’ reports and not inspected directly.

[2] Jaap Mansfeld and David Runia, “Doxography of Ancient Philosophy”, Stanford Encyclopedia of Philosophy, revised 10 June 2024, for the distinction between evidence and the purposes of those who transmit it. Doxography means the recording of earlier thinkers’ views. The opening and §§5–8 were read, and earlier sections were consulted only in part; neither the complete entry nor the works it cites were read.

[3] Daniel W. Graham, “Heraclitus”, Stanford Encyclopedia of Philosophy, revised 8 December 2023, for an attributed interpretation of the river fragment and a comparison of how the river sayings were transmitted. The opening and §§1–3.2 were read, especially §3.1 on B12, the competing river formulations and Plato’s Cratylus 402a. Graham’s account is not a settled scholarly verdict, and it does not stand in for a full reading of Plato’s dialogue.

[4] John Palmer, “Parmenides”, Stanford Encyclopedia of Philosophy, revised 4 March 2025, for how the poem was preserved, its argument and the limits of interpretation. The opening, §1 and §§2.1–2.3 were read, with the opening of §2.4. The complete entry was not read, and Palmer’s preferred interpretation is not assumed to settle the debate.

The potter, the fountain and the optional response are original teaching material. No independent Greek-language collation was undertaken, and no independent specialist or learner has reviewed this lesson. The evidence supports a limited comparison, not a complete account of either thinker.