Abstract: This essay offers an original interpretation and defense of the doctrine of flux, as it is presented in Plato’s Theaetetus. The methodology of the paper’s analysis is in the style of rational reconstruction, and it is highly analytic in scope, in the sense that I will focus on the text itself, and only on certain parts of it too, while ignoring the rest of Plato’s extensive corpus, and without worrying about whether, how, and to what extent the interpretation of the view coheres well with the other elements of the secret doctrine view discussed in the dialogue, as well. In the first part of the essay, I’ll offer my interpretation of the doctrine. Then, in the second part of the essay, I’ll examine two potential criticisms of the doctrine, including Socrates’s infamous linguistic paradox, and show how my interpretation of Heraclitean flux metaphysics is able to circumvent both.

Key Words: Plato’s Theaetetus; Heraclitus, flux metaphysics; structuralism; process philosophy; dynamism; philosophical cosmology