Tao te Ching: 40

Reversion is the action of Tao.
Weakness is the function of Tao.
All things in the world come from being.
And being comes from non-being.

When looking at the Tao, always look backward. Everything depends on its base—on what it originates from. Very much like the Buddhist doctrine of dependent arising, things depend on being, and being depends on non-being.

This is the shortest chapter in the Tao te Ching, but it is a very profound restatement of the basic philosophy, if you have read the rest of the chapters.

Reversion also has another meaning. I've been thinking about it for a while. There is a story that Chuang Tzu and his disciple were walking through the mountains when they saw an enormous oak tree. A lumberjack was standing next to the tree but he wasn't cutting it down. Chuang Tzu asked why he didn't cut it down, and the lumberjack said it was of no use. So Chuang Tzu said "Because the tree has no exceptional qualities, it is able to live out its entire life."

Later, Chuang Tzu stops at a friends house for supper and the friend orders a goose to be killed for dinner. The servant says they have two geese, one that can cackle and one that cannot. Which should be killed? Chuang Tzu said to kill the mute one. The disciple said, "Hold on, Master. The tree lived because it had no exceptional qualities but the goose dies for the same reason? You need to pick a side." Chuang Tzu replies, "I pick somewhere in the middle. Even that isn't exactly right, because even one who stays in the middle will occasionally experience trouble."

You can think of reversion as playing "military golf."  You know—left, right, left, right...

When something gets to one far extreme, it becomes the other far extreme. I think this is probably easiest to see in politics. The most liberal of people become conservative once they have their way and those conservatives displaced by the former liberals become radicalized and attempt to bring about something new (the old ways seeming new). Hence why politics seems cyclical. Or fashion. Wars. Everything, really.

The man who goes to extremes eventually becomes his antithesis. Those who stay to the middle path are preserved.