反馈是一个强大的概念，在自然系统和技术系统中被广泛使用。

I can never be safe; I always try and go against the grain. As soon as I accomplish one thing, I just set a higher goal. That’s how I’ve gotten to where I am.

The Moving Finger writes; and, having writ, Moves on: nor all thy Piety nor Wit Shall lure it back to cancel half a Line, Nor all thy Tears wash out a Word of it.