Chapter eight contains the book's most durable image. The highest good is like water, which benefits the ten thousand things without contending, and which settles in the places people dislike, and so comes close to the way.
Every element of that is doing work. Water benefits universally and without selection, which matches the impartiality of chapter five. It does not contend, and yet chapter seventy-eight will point out that nothing surpasses it for wearing down what is hard. And it goes downward, always, without exception, to exactly the low ground that people avoid, which connects it to the valley of chapter six and the estuary of chapter sixty-one.
The reason the figure has lasted is that it is not a metaphor for a virtue. It is an observation about a substance with properties anyone can check. Water genuinely does take the shape of whatever contains it, genuinely does find the lowest available point, genuinely does cut rock given time, and genuinely cannot be compressed or gripped. A reader is not being asked to accept a comparison; they are being asked to notice something they already know.
Later Daoist and Chinese Buddhist writing used the image so heavily that it became a commonplace, and it travelled well beyond the tradition. It is the one chapter of this book that people who have never opened it are likely to be able to paraphrase.