The water in the river keeps flowing. This time you stepped into the river and the water ran away. Next time you step into the river, new water will flow. The river keeps flowing, so you can't step into the same river. Obviously, this famous saying has its specific meaning, not the difference between this river and that river. Heraclitus advocated "the movement of all things" and "the flow of all things", which made him an outstanding representative of the "mobile school" with simple dialectical thought at that time. Heraclitus' famous saying shows that objective things are always moving. Such a changing and developing truth. Engels once commented: "This primitive, simple but essentially correct world view is the world view of ancient Greek philosophy, and it was clearly expressed by Heraclitus for the first time: everything exists, but it does not exist, because everything is fluid, constantly changing, constantly producing and disappearing." Heraclitus also believes that everything is transformed into each other. Cold becomes hot, hot becomes cold, wet becomes dry, and dry becomes wet. He also clearly asserted: "We didn't go down the same river. We exist and don't exist. "