On the 4th of December 1872 Charles Darwin wrote to Alpheus Hyatt at Harvard. In the letter he said: "after long reflection I can not avoid the conviction that no innate tendency to progressive development exists ". (The italics are mine.)

Ronnie Brown writes:

But perhaps there is a tendency to complexity, governed by the geometry of forms, and the laws of physics. This development also seems to evolve on the border between chaos and total stability, fed by energy, and allowing complex forms to evolve and interact.