The sun is new every day. Comparing existence to a river, one cannot step into the same river twice. Because when people enter the river for the second time, it is a new water flow instead of the original one.

Heraclitus summed up his views on movement change in very concise language: everything is flowing, and nothing is eternal. In his opinion. Nothing in the universe is absolutely static, everything is moving and changing.

Extended data:

There is a process in the development of dialectics, which combines speculation with demonstration. The first stage of dialectics development is to reach the truth through debate, which is the thinking stage of dialectics development; The second stage is to reveal the universal law of the development of the universe, which is the empirical stage of the development of dialectics; The third stage is the unity of speculation and demonstration, which is the synthesis of the first two stages, that is, the unity of speculation and demonstration.

If the first stage is the dialectics of epistemology, the second stage is the dialectics of ontology, and the third stage is the symmetrical dialectics of the unity of ontology and epistemology. Symmetric dialectics is the unity of speculative dialectics and empirical dialectics, and it is the highest stage of dialectics development.

References:

Baidu Encyclopedia-People can't step into the same river twice