Gregory Rowden: ‘You never step into the same river twice’ (Heraclitus)

What did Heraclitus mean by his famous assertion that we can never step into the same river twice?

Heraclitus rejected the monist theories of Thales, Anaximander, and Anaximenes and instead argued for a process of continual law-like flux. His assertion that we can never step into the same river twice used an analogy to argue that everything is in flux; the river is constantly changing therefore the next time we step into the river it has changed. The problem of what Heraclitus meant by this assertion is compounded by the fact that there are several conflicting fragments from different authors. Two of the main interpretations of the fragments are the radical flux and moderate flux views. I argue that neither of these views on their own adequately accounts for the entire meaning of Heraclitus assertion and I propose an alternative interpretation.

Proponents of the radical flux view refer to Plato’s comment in Cratylus; “Heraclitus, you know, says that everything moves on and that nothing is at rest; and, comparing existing things to the flow of a river, he says that you could not step into the same river twice”. Guthrie argued that if we take Plato’s assertion as authentic then Heraclitus is arguing by this statement that everything, with the exception of the Logos, is constantly changing in every respect. When we step into the river for the second time not only has the water changed but so has the river itself. Plato’s interpretation denies any persisting objects, since all is in flux, thus supporting his Theory of Forms. There are however reasons why we should doubt Plato’s interpretation of radical flux. First, Guthrie argued that Aristotle wrote that Heraclitus had a profound influence on Plato, leading him to his Theory of Forms; therefore Plato must be authentic with his interpretation. However it is equally arguable that Plato may have distorted Heraclitus’ remarks, making them more in alignment with his own theories. This is further supported by the fact that in other dialogues Plato makes Socrates distort the ideas of other philosophers for his own purpose. However, it is just as likely that Plato truly believed that Heraclitus’ theory denied any persisting objects, and was merely mistaken. Based on the information we have available today, we do not have a strong enough reason to believe that by proposing all was in flux, Heraclitus was also making the assertion against material existence.

The second interpretation of Heraclitus’ assertion is the moderate flux view. Proponents argue that fragment B12 is authentic; “Upon those who step into the same rivers flow other and yet other waters”. Here fragment B12 is radically different in asserting that everything is not changing, only that some things are changing, while others stay the same. Instead of the universal flux theory Plato has Heraclitus arguing for, fragment B12 views a systematic, orderly, continuous changing of the elements. Kirk and Marcovich argued that fragment B12 is the only correct reading of Heraclitus’ theory. Even if material things are more process than static, the same object can endure even though it is undergoing constant change. In fact only by changing can some things remain the same. If the river ceased changing, it would cease to be a river. The main concern with this

interpretation is that to accept flux and monism as coexisting principles is to deny the law of non-contradiction. As a result the moderate view cannot be considered a viable interpretation as it is unlikely that Heraclitus would have proposed a theory that resulted in logical chaos.

I believe that Heraclitus was proposing that not only were some things in constant flux, as in the moderate view, but that all is in flux in every manner. However unlike Plato’s interpretation, I believe that Heraclitus does not to deny existence. The waters are constantly changing, the rivers are constantly changing, but they still exist. I believe that Heraclitus never intended that flux was separate from existence. Every cell in my body is under constant change and it cannot be inferred that I remain the same, this would be contradictory. If my parts change, my whole must also change. This change however is not random, but governed by the Logos. To accept the moderate view is to accept that some entities are permanent and modern science tells us this is not true. Even the most obvious seeming material entity, the rock, changes over time in what is known as “rock cycles” through changes in temperature and heat. If the waters change in the river, how can it be the same river? As the part changes, so does the whole. I believe Heraclitus is claiming that all, including the cosmos itself, is in a state of flux, but this need not assume the change is at random. This universal flux is systematic and logical, in accordance with his theories on the Logos and the Unity of Opposites. For Heraclitus, I believe, flux is a condition of existence in the same manner that the dynamic continuum is a condition of existence.

I believe it is unlikely that Plato’s portrayal of Heraclitus’ theory of flux is accurate. Heraclitus was not denying the coexistence of change and permanence. Likewise, I believe he held that all things, not just some parts, were changing at all times. This was also the Stoic interpretation, who subsequently adopted the views of Heraclitus as their own theories of “physics”. The Stoics claimed that everything is in state of flux at all times. Everything rises and passes away, the water rises and passes away as does the river itself. However the constant changing of the river does not negate its existence. Its existence is not in a static, but dynamic state. I believe the radical and moderate views were only partially correct. It is the Stoic view, I believe, that is the true interpretation of Heraclitus’ famous assertion.


Burnet, J. (1920). Early Greek Philosophy. A and C Black: London.

Guthrie, W.K.C. (1974). The Presocratics. Anchor Press: New York

Inwood, B. (2003). The Cambridge Companion to The Stoics. Cambridge University Press: New York, NY.

Kirk, G.S., Raven, J.E. & Schofield, M. (1957). The Presocratic Philosophers.

Cambridge University Press: New York, NY.

Plato. Cratylus. Parmenides. Greater Hippias. Lesser Hippias. Trans. H.N. Fowler.

Cambridge: Harvard UP, 1926.

Vlastos, G. (1995). On Heraclitis. The American Journal of Philology, 76 (4), 337-368.

© Gregory Rowden 2018