Everything in the world is spent in change.

For example, cells in your body are dying and reborn every minute, so this can lead to a question: Do you know yourself now, especially in the external material world, when human existence cannot be recognized?

However, although the external physical world cannot be recognized, it can still maintain and count certain laws, that is to say, although people can't step into the same river, they still confirm that they are a river.

And this sentence is not so much the movement of things as the movement of time. If you regard time as a river, the same result is clearly visible.