All is Revealed
Where Parmenides saw only unity of Being, Heracleitus saw constant Becoming. Although he speaks in metaphor, Heracleitus' meaning is clear enough. Nothing is permanent. Everything is changing. The only permanent feature of things is their constant transformation.
This most famous part of his doctrine came to be encapsulated in the phrase "all things are flowing":
"It is impossible to descend twice into the same river and it is impossible to touch a mortal substance twice in the same condition, but because of the impetuosity and speed of the changes, it is scattered and gathered together, it comes and it goes."Heracleitus conceives of a world of constant change and conflict, but not a world of chaos. Opposites exist on a continuum: "The way up and down is one and the same." His is a world in which the interaction, the tension, of opposites, is a creative force with fire as the principle element of nature and creation. This he identified with what he termed the Logos, a sort of world soul which permeated and governed all life.
"All things come into being by conflict of opposites, and the sum of things flows like a stream. Further, everything that is, is limited, and forms one world which is alternately born from fire and again resolved into fire in fixed cycles for all eternity... For fire, by contracting turns into moisture, and this condensing, turns into water; water again when congealed turns to earth."Diogenes Laertius IX. 8,9